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<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE book PUBLIC "-//FreeBSD//DTD DocBook XML V5.0-Based Extension//EN"
"http://www.FreeBSD.org/XML/share/xml/freebsd50.dtd" [
<!ENTITY bibliography SYSTEM "../../../share/xml/bibliography.xml">
<!ENTITY rel.numbranch "3"> <!-- number of branches that follow in this list -->
<!ENTITY rel.head "<emphasis xmlns='http://docbook.org/ns/docbook'>12-CURRENT</emphasis>">
<!ENTITY rel.head.relx "12.<replaceable xmlns='http://docbook.org/ns/docbook'>X</replaceable>">
<!ENTITY rel.head.releng "<symbol xmlns='http://docbook.org/ns/docbook'>head/</symbol>">
<!ENTITY rel.relx "11.<replaceable xmlns='http://docbook.org/ns/docbook'>X</replaceable>">
<!ENTITY rel.stable "<emphasis xmlns='http://docbook.org/ns/docbook'>11-STABLE</emphasis>">
<!ENTITY rel.releng "<symbol xmlns='http://docbook.org/ns/docbook'>stable/11/</symbol>">
<!ENTITY rel.relengdate "April 2016">
<!ENTITY rel2.relx "10.<replaceable xmlns='http://docbook.org/ns/docbook'>X</replaceable>">
<!ENTITY rel2.stable "<emphasis xmlns='http://docbook.org/ns/docbook'>10-STABLE</emphasis>">
<!ENTITY rel2.releng "<symbol xmlns='http://docbook.org/ns/docbook'>stable/10/</symbol>">
<!ENTITY rel2.relengdate "August 2015">
]>
<book xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0" xml:lang="en">
<info>
<title>Frequently Asked Questions for &os;
&rel2.relx; and &rel.relx;</title>
<author><orgname>The &os; Documentation Project</orgname></author>
<copyright>
<year>1995</year>
<year>1996</year>
<year>1997</year>
<year>1998</year>
<year>1999</year>
<year>2000</year>
<year>2001</year>
<year>2002</year>
<year>2003</year>
<year>2004</year>
<year>2005</year>
<year>2006</year>
<year>2007</year>
<year>2008</year>
<year>2009</year>
<year>2010</year>
<year>2011</year>
<year>2012</year>
<year>2013</year>
<year>2014</year>
<year>2015</year>
<year>2016</year>
<year>2017</year>
<holder>The &os; Documentation Project</holder>
</copyright>
&legalnotice;
<legalnotice xml:id="trademarks" role="trademarks">
&tm-attrib.freebsd;
&tm-attrib.adobe;
&tm-attrib.ibm;
&tm-attrib.ieee;
&tm-attrib.intel;
&tm-attrib.linux;
&tm-attrib.microsoft;
&tm-attrib.netbsd;
&tm-attrib.opengroup;
&tm-attrib.sgi;
&tm-attrib.sun;
&tm-attrib.general;
</legalnotice>
<releaseinfo>$FreeBSD$</releaseinfo>
<abstract>
<para>This is the Frequently Asked Questions
<acronym>(FAQ)</acronym> for &os; versions
&rel2.relx; and &rel.relx;. Every effort has been made to
make this <acronym>FAQ</acronym> as informative as possible;
if you have any suggestions as to how it may be improved, send
them to the &a.doc;.</para>
<para>The latest version of this document is always available
from the <link
xlink:href="https://www.FreeBSD.org/doc/en_US.ISO8859-1/books/faq/index.html">&os;
website</link>. It may also be downloaded as one large
<link xlink:href="book.html">HTML</link> file with HTTP or as
a variety of other formats from the <link
xlink:href="https://download.freebsd.org/ftp/doc/">&os; FTP
server</link>.</para>
</abstract>
</info>
<chapter xml:id="introduction">
<title>Introduction</title>
<qandaset>
<qandaentry>
<question xml:id="what-is-FreeBSD">
<para>What is &os;?</para>
</question>
<answer>
<para>&os; is a modern operating system for desktops,
laptops, servers, and embedded systems with support for a
large number of <link
xlink:href="https://www.FreeBSD.org/platforms/">platforms</link>.</para>
<para>It is based on U.C. Berkeley's
<quote>4.4BSD-Lite</quote> release, with some
<quote>4.4BSD-Lite2</quote> enhancements. It is also
based indirectly on William Jolitz's port of U.C.
Berkeley's <quote>Net/2</quote> to the &i386;, known as
<quote>386BSD</quote>, though very little of the 386BSD
code remains.</para>
<para>&os; is used by companies, Internet Service Providers,
researchers, computer professionals, students and home
users all over the world in their work, education and
recreation.</para>
<para>For more detailed information on &os;, refer to the
<link xlink:href="&url.books.handbook;/index.html">&os;
Handbook</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="FreeBSD-goals">
<para>What is the goal of the &os; Project?</para>
</question>
<answer>
<para>The goal of the &os; Project is to provide a stable
and fast general purpose operating system that may be used
for any purpose without strings attached.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="bsd-license-restrictions">
<para>Does the &os; license have any restrictions?</para>
</question>
<answer>
<para>Yes. Those restrictions do not control how the code
is used, but how to treat the &os; Project itself.
The license itself is available at
<link
xlink:href="https://www.FreeBSD.org/copyright/freebsd-license.html">license</link>
and can be summarized like this:</para>
<itemizedlist>
<listitem>
<para>Do not claim that you wrote this.</para>
</listitem>
<listitem>
<para>Do not sue us if it breaks.</para>
</listitem>
<listitem>
<para>Do not remove or modify the license.</para>
</listitem>
</itemizedlist>
<para>Many of us have a significant investment in the
project and would certainly not mind a little financial
compensation now and then, but we definitely do not insist
on it. We believe that our first and foremost
<quote>mission</quote> is to provide code to any and all
comers, and for whatever purpose, so that the code gets
the widest possible use and provides the widest possible
benefit. This, we believe, is one of the most fundamental
goals of Free Software and one that we enthusiastically
support.</para>
<para>Code in our source tree which falls under the <link
xlink:href="https://www.FreeBSD.org/copyright/COPYING">GNU
General Public License (GPL)</link> or <link
xlink:href="https://www.FreeBSD.org/copyright/COPYING.LIB">GNU
Library General Public License (LGPL)</link> comes with
slightly more strings attached, though at least on the
side of enforced access rather than the usual opposite.
Due to the additional complexities that can evolve in the
commercial use of GPL software, we do, however, endeavor
to replace such software with submissions under the more
relaxed <link
xlink:href="https://www.FreeBSD.org/copyright/freebsd-license.html">&os;
license</link> whenever possible.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="replace-current-OS">
<para>Can &os; replace my current operating system?</para>
</question>
<answer>
<para>For most people, yes. But this question is not quite
that cut-and-dried.</para>
<para>Most people do not actually use an operating system.
They use applications. The applications are what really
use the operating system. &os; is designed to provide a
robust and full-featured environment for applications. It
supports a wide variety of web browsers, office suites,
email readers, graphics programs, programming
environments, network servers, and much more.
Most of these applications can be
managed through the <link
xlink:href="https://www.FreeBSD.org/ports/">Ports
Collection</link>.</para>
<para>If an application is only available on one operating
system, that operating system cannot just be replaced.
Chances are, there is a very similar application on &os;,
however. As a solid office or Internet server or a
reliable workstation, &os; will almost certainly do
everything you need. Many computer users across the
world, including both novices and experienced &unix;
administrators, use &os; as their only desktop operating
system.</para>
<para>Users migrating to &os; from another &unix;-like
environment will find &os; to be similar.
&windows; and &macos; users may be interested in instead
using <link
xlink:href="https://www.trueos.org">TrueOS</link>, a
&os;-based desktop distribution. Non-&unix; users should
expect to invest some additional time learning the
&unix; way of doing things. This <acronym>FAQ</acronym>
and the <link
xlink:href="&url.books.handbook;/index.html">&os;
Handbook</link> are excellent places to start.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="why-called-FreeBSD">
<para>Why is it called &os;?</para>
</question>
<answer>
<itemizedlist>
<listitem>
<para>It may be used free of charge, even by commercial
users.</para>
</listitem>
<listitem>
<para>Full source for the operating system is freely
available, and the minimum possible restrictions have
been placed upon its use, distribution and
incorporation into other work (commercial or
non-commercial).</para>
</listitem>
<listitem>
<para>Anyone who has an improvement or bug fix is free
to submit their code and have it added to the source
tree (subject to one or two obvious
provisions).</para>
</listitem>
</itemizedlist>
<para>It is worth pointing out that the word
<quote>free</quote> is being used in two ways here: one
meaning <quote>at no cost</quote> and the other meaning
<quote>do whatever you like</quote>. Apart from
one or two things you <emphasis>cannot</emphasis> do with
the &os; code, for example pretending you wrote it, you
can really do whatever you like with it.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="differences-to-other-bsds">
<para>What are the differences between &os; and NetBSD,
OpenBSD, and other open source BSD operating
systems?</para>
</question>
<answer>
<para>James Howard wrote a good explanation of the history
and differences between the various projects, called <link
xlink:href="https://jameshoward.us/archive/the-bsd-family-tree/">The
BSD Family Tree</link> which goes a fair way to
answering this question. Some of the information is out
of date, but the history portion in particular remains
accurate.</para>
<para>Most of the BSDs share patches and code, even today.
All of the BSDs have common ancestry.</para>
<para>The design goals of &os; are described in <xref
linkend="FreeBSD-goals"/>, above. The design goals of
the other most popular BSDs may be summarized as
follows:</para>
<itemizedlist>
<listitem>
<para>OpenBSD aims for operating system security above
all else. The OpenBSD team wrote &man.ssh.1; and
&man.pf.4;, which have both been ported to
&os;.</para>
</listitem>
<listitem>
<para>NetBSD aims to be easily ported to other hardware
platforms.</para>
</listitem>
<listitem>
<para>DragonFly&nbsp;BSD is a fork of &os;&nbsp;4.8 that
has since developed many interesting features of its
own, including the HAMMER file system and support for
user-mode <quote>vkernels</quote>.</para>
</listitem>
</itemizedlist>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="latest-version">
<para>What is the latest version of &os;?</para>
</question>
<answer>
<para>At any point in the development of &os;, there can be
multiple parallel branches. &rel.relx; releases are made
from the &rel.stable; branch, and &rel2.relx; releases are
made from the &rel2.stable; branch.</para>
<para>Up until the release of 9.0, the &rel2.relx; series
was the one known as <emphasis>-STABLE</emphasis>.
However, as of &rel.head.relx;, the &rel2.relx; branch
will be designated for an <quote>extended support</quote>
status and receive only fixes for major problems, such as
security-related fixes.
<!--There will be no more releases made from the
&rel2.stable; branch, and it is considered a
<quote>legacy</quote> branch and most current work will only
become a part of &rel.stable; and &rel2.stable;.--></para>
<para>Version <link
xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/releases/i386/i386/&rel.current;-RELEASE/">&rel.current;</link>
is the latest release from the &rel.stable; branch; it was
released in &rel.current.date;. Version <link
xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/releases/i386/&rel2.current;-RELEASE/">&rel2.current;</link>
is the latest release from the &rel2.stable; branch; it
was released in &rel2.current.date;.</para>
<para>Releases are made <link linkend="release-freq">every
few months</link>. While many people stay more
up-to-date with the &os; sources (see the questions on
<link linkend="current">&os.current;</link> and <link
linkend="stable">&os.stable;</link>) than that, doing so
is more of a commitment, as the sources are a moving
target.</para>
<para>More information on &os; releases can be found on the
<link
xlink:href="https://www.FreeBSD.org/releng/index.html#release-build">Release
Engineering page</link> and in &man.release.7;.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="current">
<para>What is <emphasis>&os;-CURRENT</emphasis>?</para>
</question>
<answer>
<para><link
xlink:href="&url.books.handbook;/current-stable.html#current">&os.current;</link>
is the development version of the operating system, which
will in due course become the new &os.stable; branch. As
such, it is really only of interest to developers working
on the system and die-hard hobbyists. See the <link
xlink:href="&url.books.handbook;/current-stable.html#current">relevant
section</link> in the <link
xlink:href="&url.books.handbook;/index.html">Handbook</link>
for details on running
<emphasis>-CURRENT</emphasis>.</para>
<para>Users not familiar with &os; should not use
&os.current;. This branch sometimes evolves quite quickly
and due to mistake can be un-buildable at times. People
that use &os.current; are expected to be able to analyze,
debug, and report problems.</para>
<para>&os; <link
xlink:href="&url.base;/snapshots/">snapshot</link>
releases are made based on the current state of the
<emphasis>-CURRENT</emphasis> and
<emphasis>-STABLE</emphasis> branches. The goals behind
each snapshot release are:</para>
<itemizedlist>
<listitem>
<para>To test the latest version of the installation
software.</para>
</listitem>
<listitem>
<para>To give people who would like to run
<emphasis>-CURRENT</emphasis> or
<emphasis>-STABLE</emphasis> but who do not have the
time or bandwidth to follow it on a day-to-day basis
an easy way of bootstrapping it onto their
systems.</para>
</listitem>
<listitem>
<para>To preserve a fixed reference point for the code
in question, just in case we break something really
badly later. (Although Subversion normally prevents
anything horrible like this happening.)</para>
</listitem>
<listitem>
<para>To ensure that all new features and fixes in need
of testing have the greatest possible number of
potential testers.</para>
</listitem>
</itemizedlist>
<para>No claims are made that any
<emphasis>-CURRENT</emphasis> snapshot can be considered
<quote>production quality</quote> for any purpose.
If a stable and fully tested system is needed,
stick to full releases.</para>
<para>Snapshot releases are directly available from <link
xlink:href="&url.base;/snapshots/">snapshot</link>.</para>
<para>Official snapshots are generated on a regular
basis for all actively developed branches.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="stable">
<para>What is the <emphasis>&os;-STABLE</emphasis>
concept?</para>
</question>
<answer>
<para>Back when &os;&nbsp;2.0.5 was released, &os;
development branched in two. One branch was named <link
xlink:href="&url.books.handbook;/current-stable.html#stable">-STABLE</link>,
one <link
xlink:href="&url.books.handbook;/current-stable.html#current">-CURRENT</link>.
<emphasis>&os;-STABLE</emphasis> is the development branch
from which major releases are made. Changes go into this
branch at a slower pace and with the general assumption
that they have first been tested in &os;-CURRENT.
However, at any given time, the sources for &os;-STABLE
may or may not be suitable for general use, as it may
uncover bugs and corner cases that were not yet found in
&os;-CURRENT. Users who do not have the resources to
perform testing should instead run the most recent release
of &os;.
<emphasis>&os;-CURRENT</emphasis>, on the other hand, has
been one unbroken line since 2.0 was released, leading
towards &rel.current;-RELEASE and beyond. For more
detailed information on branches see <quote><link
xlink:href="&url.articles.releng;/release-proc.html#rel-branch">&os;
Release Engineering: Creating the Release
Branch</link></quote>, the status of the branches and
the upcoming release schedule can be found on the <link
xlink:href="https://www.FreeBSD.org/releng">Release
Engineering Information</link> page.</para>
<para>&rel.current;-STABLE is the actively developed
<emphasis>-STABLE</emphasis> branch. The latest release
on the &rel.current;-STABLE branch is
&rel.current;-RELEASE, which was released in
&rel.current.date;.</para>
<para>The &rel.head; branch is the actively developed
<emphasis>-CURRENT</emphasis> branch toward the next
generation of &os;. See <link linkend="current">What is
&os;-CURRENT?</link> for more information on this
branch.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="release-freq">
<para>When are &os; releases made?</para>
</question>
<answer>
<para>The &a.re; releases a new major version of &os; about
every 18 months and a new minor version about every 8
months, on average. Release dates are announced well in
advance, so that the people working on the system know
when their projects need to be finished and tested. A
testing period precedes each release, to ensure that the
addition of new features does not compromise the stability
of the release. Many users regard this caution as one of
the best things about &os;, even though waiting for all
the latest goodies to reach <emphasis>-STABLE</emphasis>
can be a little frustrating.</para>
<para>More information on the release engineering process
(including a schedule of upcoming releases) can be found
on the <link
xlink:href="https://www.FreeBSD.org/releng/index.html">release
engineering</link> pages on the &os; Web site.</para>
<para>For people who need or want a little more excitement,
binary snapshots are made weekly as discussed
above.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="responsible">
<para>Who is responsible for &os;?</para>
</question>
<answer>
<para>The key decisions concerning the &os; project, such as
the overall direction of the project and who is allowed to
add code to the source tree, are made by a <link
xlink:href="&url.base;/administration.html#t-core">core
team</link> of 9 people. There is a much larger team of
more than 350 <link
xlink:href="&url.articles.contributors;/article.html#staff-committers">committers</link>
who are authorized to make changes directly to the &os;
source tree.</para>
<para>However, most non-trivial changes are discussed in
advance in the <link linkend="mailing">mailing
lists</link>, and there are no restrictions on who may
take part in the discussion.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="where-get">
<para>Where can I get &os;?</para>
</question>
<answer>
<para>Every significant release of &os; is available via
anonymous FTP from the <link
xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/"> &os;
FTP site</link>:</para>
<itemizedlist>
<listitem>
<para>The latest &rel.stable; release,
&rel.current;-RELEASE can be found in the <link
xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/releases/i386/i386/&rel.current;-RELEASE/">&rel.current;-RELEASE
directory</link>.</para>
</listitem>
<listitem>
<para><link
xlink:href="&url.base;/snapshots/">Snapshot</link>
releases are made monthly for the <link
linkend="current">-CURRENT</link> and <link
linkend="stable">-STABLE</link> branch, these being
of service purely to bleeding-edge testers and
developers.</para>
</listitem>
<listitem>
<para>The latest &rel2.stable; release,
&rel2.current;-RELEASE can be found in the <link
xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/releases/i386/&rel2.current;-RELEASE/">&rel2.current;-RELEASE
directory</link>.</para>
</listitem>
</itemizedlist>
<para>Information about obtaining &os; on CD, DVD, and other
media can be found in <link
xlink:href="&url.books.handbook;/mirrors.html">the
Handbook</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="access-pr">
<para>How do I access the Problem Report database?</para>
</question>
<answer>
<para>The Problem Report database of all user change
requests may be queried by using our web-based PR <link
xlink:href="https://bugs.FreeBSD.org/search/">query</link>
interface.</para>
<para>The <link
xlink:href="&url.base;/support/bugreports.html">web-based
problem report submission interface</link> can be used
to submit problem reports through a web browser.</para>
<para>Before submitting a problem report, read <link
xlink:href="&url.articles.problem-reports;/article.html">Writing
&os; Problem Reports</link>, an article on how to write
good problem reports.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="support">
<title>Documentation and Support</title>
<qandaset>
<qandaentry>
<question xml:id="books">
<para>What good books are there about &os;?</para>
</question>
<answer>
<para>The project produces a wide range of documentation,
available online from this link: <uri
xlink:href="https://www.FreeBSD.org/docs.html">https://www.FreeBSD.org/docs.html</uri>.
In addition, <link
linkend="bibliography">the Bibliography</link> at the
end of this <acronym>FAQ</acronym>, and <link
xlink:href="&url.books.handbook;/bibliography.html">the
one in the Handbook</link> reference other recommended
books.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="doc-formats">
<para>Is the documentation available in other formats, such
as plain text (ASCII), or &postscript;?</para>
</question>
<answer>
<para>Yes. The documentation is available in a number of
different formats and compression schemes on the &os; FTP
site, in the <link
xlink:href="https://download.freebsd.org/ftp/doc/">/pub/FreeBSD/doc/</link>
directory.</para>
<para>The documentation is categorized in a number of
different ways. These include:</para>
<itemizedlist>
<listitem>
<para>The document's name, such as
<literal>faq</literal>, or
<literal>handbook</literal>.</para>
</listitem>
<listitem>
<para>The document's language and encoding. These are
based on the locale names found under
<filename>/usr/share/locale</filename> on a &os;
system. The current languages and encodings
are as follows:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>Name</entry>
<entry>Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>en_US.ISO8859-1</literal></entry>
<entry>English (United States)</entry>
</row>
<row>
<entry><literal>bn_BD.ISO10646-1</literal></entry>
<entry>Bengali or Bangla (Bangladesh)</entry>
</row>
<row>
<entry><literal>da_DK.ISO8859-1</literal></entry>
<entry>Danish (Denmark)</entry>
</row>
<row>
<entry><literal>de_DE.ISO8859-1</literal></entry>
<entry>German (Germany)</entry>
</row>
<row>
<entry><literal>el_GR.ISO8859-7</literal></entry>
<entry>Greek (Greece)</entry>
</row>
<row>
<entry><literal>es_ES.ISO8859-1</literal></entry>
<entry>Spanish (Spain)</entry>
</row>
<row>
<entry><literal>fr_FR.ISO8859-1</literal></entry>
<entry>French (France)</entry>
</row>
<row>
<entry><literal>hu_HU.ISO8859-2</literal></entry>
<entry>Hungarian (Hungary)</entry>
</row>
<row>
<entry><literal>it_IT.ISO8859-15</literal></entry>
<entry>Italian (Italy)</entry>
</row>
<row>
<entry><literal>ja_JP.eucJP</literal></entry>
<entry>Japanese (Japan, EUC encoding)</entry>
</row>
<row>
<entry><literal>mn_MN.UTF-8</literal></entry>
<entry>Mongolian (Mongolia, UTF-8
encoding)</entry>
</row>
<row>
<entry><literal>nl_NL.ISO8859-1</literal></entry>
<entry>Dutch (Netherlands)</entry>
</row>
<row>
<entry><literal>no_NO.ISO8859-1</literal></entry>
<entry>Norwegian (Norway)</entry>
</row>
<row>
<entry><literal>pl_PL.ISO8859-2</literal></entry>
<entry>Polish (Poland)</entry>
</row>
<row>
<entry><literal>pt_BR.ISO8859-1</literal></entry>
<entry>Portuguese (Brazil)</entry>
</row>
<row>
<entry><literal>ru_RU.KOI8-R</literal></entry>
<entry>Russian (Russia, KOI8-R encoding)</entry>
</row>
<row>
<entry><literal>sr_YU.ISO8859-2</literal></entry>
<entry>Serbian (Serbia)</entry>
</row>
<row>
<entry><literal>tr_TR.ISO8859-9</literal></entry>
<entry>Turkish (Turkey)</entry>
</row>
<row>
<entry><literal>zh_CN.UTF-8</literal></entry>
<entry>Simplified Chinese (China, UTF-8
encoding)</entry>
</row>
<row>
<entry><literal>zh_TW.UTF-8</literal></entry>
<entry>Traditional Chinese (Taiwan, UTF-8
encoding)</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<note>
<para>Some documents may not be available in all
languages.</para>
</note>
</listitem>
<listitem>
<para>The document's format. We produce the
documentation in a number of different output formats.
Each format has its own advantages and disadvantages.
Some formats are better suited for online reading,
while others are meant to be aesthetically pleasing
when printed on paper. Having the documentation
available in any of these formats ensures that our
readers will be able to read the parts they are
interested in, either on their monitor, or on paper
after printing the documents. The currently available
formats are:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>Format</entry>
<entry>Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>html-split</literal></entry>
<entry>A collection of small, linked, HTML
files.</entry>
</row>
<row>
<entry><literal>html</literal></entry>
<entry>One large HTML file containing the entire
document</entry>
</row>
<row>
<entry><literal>pdf</literal></entry>
<entry>Adobe's Portable Document Format</entry>
</row>
<row>
<entry><literal>ps</literal></entry>
<entry>&postscript;</entry>
</row>
<row>
<entry><literal>rtf</literal></entry>
<entry>&microsoft;'s Rich Text Format</entry>
</row>
<row>
<entry><literal>txt</literal></entry>
<entry>Plain text</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<note>
<para>Page numbers are not automatically updated when
loading Rich Text Format into Word. Press <keycombo
action="simul"><keycap>Ctrl</keycap><keycap>A</keycap></keycombo>,
<keycombo
action="simul"><keycap>Ctrl</keycap><keycap>End</keycap></keycombo>,
<keycap>F9</keycap> after loading the document, to
update the page numbers.</para>
</note>
</listitem>
<listitem>
<para>The compression and packaging scheme.</para>
<orderedlist>
<listitem>
<para>Where the format is
<literal>html-split</literal>, the files are
bundled up using &man.tar.1;. The resulting
<filename>.tar</filename> file is then compressed
using the compression schemes detailed in the next
point.</para>
</listitem>
<listitem>
<para>All the other formats generate one file. For
example,
<filename>article.pdf</filename>,
<filename>book.html</filename>, and so on.</para>
<para>These files are then compressed using either
the <literal>zip</literal> or
<literal>bz2</literal> compression schemes.
&man.tar.1; can be used to uncompress these
files.</para>
<para>So the &postscript; version of the Handbook,
compressed using <literal>bzip2</literal> will be
stored in a file called
<filename>book.ps.bz2</filename> in the
<filename>handbook/</filename> directory.</para>
</listitem>
</orderedlist>
</listitem>
</itemizedlist>
<para>After choosing the format and compression mechanism,
download the
compressed files, uncompress them, and then copy
the appropriate documents into place.</para>
<para>For example, the split HTML version of the
<acronym>FAQ</acronym>, compressed using &man.bzip2.1;,
can be found in
<filename>doc/en_US.ISO8859-1/books/faq/book.html-split.tar.bz2</filename>
To download and uncompress that file, type:</para>
<screen>&prompt.root; <userinput>fetch https://download.freebsd.org/ftp/doc/en_US.ISO8859-1/books/faq/book.html-split.tar.bz2</userinput>
&prompt.root; <userinput>tar xvf book.html-split.tar.bz2</userinput></screen>
<para>If the file is compressed,
<application>tar</application> will automatically
detect the appropriate format and decompress it correctly,
resulting in a collection of
<filename>.html</filename> files. The main one is called
<filename>index.html</filename>, which will contain the
table of contents, introductory material, and links to the
other parts of the document.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mailing">
<para>Where do I find info on the &os; mailing lists? What
&os; news groups are available?</para>
</question>
<answer>
<para>Refer to the <link
xlink:href="&url.books.handbook;/eresources.html#eresources-mail">Handbook
entry on mailing-lists</link> and the <link
xlink:href="&url.books.handbook;/eresources-news.html">Handbook
entry on newsgroups</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="irc">
<para>Are there &os; IRC (Internet Relay Chat)
channels?</para>
</question>
<answer>
<para>Yes, most major IRC networks host a &os; chat
channel:</para>
<itemizedlist>
<listitem>
<para>Channel <literal>#FreeBSDhelp</literal> on <link
xlink:href="http://www.efnet.org/index.php">EFNet</link>
is a channel dedicated to helping &os; users.</para>
</listitem>
<listitem>
<para>Channel <literal>#FreeBSD</literal> on <link
xlink:href="http://freenode.net/">Freenode</link> is
a general help channel with many users at any time.
The conversations have been known to run off-topic for
a while, but priority is given to users with &os;
questions. Other users can help with
the basics, referring to the Handbook whenever
possible and providing links for learning more about
a particular topic. This is primarily an English
speaking channel, though it does have users from all
over the world. Non-native English speakers should
try to ask the question in English first and then
relocate to <literal>##freebsd-lang</literal> as
appropriate.</para>
</listitem>
<listitem>
<para>Channel <literal>#FreeBSD</literal> on <link
xlink:href="http://www.dal.net/">DALNET</link> is
available at <systemitem>irc.dal.net</systemitem> in
the US and <systemitem>irc.eu.dal.net</systemitem> in
Europe.</para>
</listitem>
<listitem>
<para>Channel <literal>#FreeBSD</literal> on <link
xlink:href="http://www.undernet.org/">UNDERNET</link>
is available at
<systemitem>us.undernet.org</systemitem> in the US and
<systemitem>eu.undernet.org</systemitem> in Europe.
Since it is a help channel, be prepared to read the
documents you are referred to.</para>
</listitem>
<listitem>
<para>Channel <literal>#FreeBSD</literal> on <link
xlink:href="http://www.rusnet.org.ru/">RUSNET</link>
is a Russian language channel dedicated to
helping &os; users. This is also good place for
non-technical discussions.</para>
</listitem>
<listitem>
<para>Channel <literal>#bsdchat</literal> on <link
xlink:href="http://freenode.net/">Freenode</link> is
a Traditional Chinese (UTF-8 encoding) language
channel dedicated to helping &os; users.
This is also good place for non-technical
discussions.</para>
</listitem>
</itemizedlist>
<para>The &os; wiki has a <link
xlink:href="https://wiki.freebsd.org/IrcChannels">good
list</link> of IRC channels.</para>
<para>Each of these channels are distinct and are not
connected to each other. Since their chat styles differ,
try each to find one suited to your
chat style.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="forums">
<para>Are there any web based forums to discuss &os;?</para>
</question>
<answer>
<para>The official &os; forums are located at <link
xlink:href="https://forums.FreeBSD.org/">https://forums.FreeBSD.org/</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="training">
<para>Where can I get commercial &os; training and
support?</para>
</question>
<answer>
<para><link xlink:href="http://www.ixsystems.com">iXsystems,
Inc.</link>, parent company of the <link
xlink:href="http://www.freebsdmall.com/">&os;
Mall</link>, provides commercial &os; and TrueOS
software <link
xlink:href="http://www.ixsystems.com/support">support</link>,
in addition to &os; development and tuning
solutions.</para>
<para>BSD Certification Group, Inc. provides system
administration certifications for DragonFly&nbsp;BSD,
&os;, NetBSD, and OpenBSD. Refer to <link
xlink:href="http://www.BSDCertification.org">their
site</link> for more information.</para>
<para>Any other organizations providing training and support
should contact the Project to be listed here.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="install">
<info>
<title>Installation</title>
<author>
<personname>
<firstname>Nik</firstname>
<surname>Clayton</surname>
</personname>
<affiliation>
<address>
<email>nik@FreeBSD.org</email>
</address>
</affiliation>
</author>
</info>
<qandaset>
<qandaentry>
<question xml:id="which-architecture">
<para>Which platform should I download? I have a 64
bit capable &intel; CPU,
but I only see <literal>amd64</literal>.</para>
</question>
<answer>
<para>&arch.amd64; is the term &os; uses for 64-bit
compatible x86 architectures (also known as "x86-64" or
"x64"). Most modern computers should use &arch.amd64;.
Older hardware should use &arch.i386;. When installing
on a non-x86-compatible architecture, select the
platform which best matches the hardware.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="floppy-download">
<para>Which file do I download to get &os;?</para>
</question>
<answer>
<para>On the <link
xlink:href="https://www.freebsd.org/where.html">Getting
&os;</link> page, select <literal>[iso]</literal> next
to the architecture that matches the hardware.</para>
<para>Any of the following can be used:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>file</entry>
<entry>description</entry>
</row>
</thead>
<tbody>
<row>
<entry><filename>disc1.iso</filename></entry>
<entry>Contains enough to install &os; and
a minimal set of packages.</entry>
</row>
<row>
<entry><filename>dvd1.iso</filename></entry>
<entry>Similar to <filename>disc1.iso</filename>
but with additional packages.</entry>
</row>
<row>
<entry><filename>memstick.img</filename></entry>
<entry>A bootable image sufficient for writing to a
USB stick.</entry>
</row>
<row>
<entry><filename>bootonly.iso</filename></entry>
<entry>A minimal image that requires network access
during installation to completely install
&os;.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>Full instructions on this procedure and a little bit
more about installation issues in general can be found in
the <link
xlink:href="&url.books.handbook;/bsdinstall.html">Handbook
entry on installing &os;</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="floppy-image-too-large">
<para>What do I do if the install image does not
boot?</para>
</question>
<answer>
<para>This can be caused by not downloading the image in
<emphasis>binary</emphasis> mode when using
<acronym>FTP</acronym>.</para>
<para>Some FTP clients default their transfer mode to
<emphasis>ascii</emphasis> and attempt to change any
end-of-line characters received to match the
conventions used by the client's system. This will
almost invariably corrupt the boot image. Check the
SHA-256 checksum of the downloaded boot image: if it
is not <emphasis>exactly</emphasis> that on the
server, then the download process is suspect.</para>
<para>When using a command line FTP client, type
<emphasis>binary</emphasis> at the FTP command prompt
after getting connected to the server and before
starting the download of the image.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="install-instructions-location">
<para>Where are the instructions for installing &os;?</para>
</question>
<answer>
<para>Installation instructions
can be found at <link
xlink:href="&url.books.handbook;/bsdinstall.html">Handbook
entry on installing &os;</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="need-to-run">
<para>What are the minimum requirements to run &os;?</para>
</question>
<answer>
<para>&os; requires a 486 or better PC,
64&nbsp;MB or more of RAM, and at least 1.1 GB of hard
disk space.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="custom-boot-floppy">
<para>How can I make my own custom release or install
disk?</para>
</question>
<answer>
<para>Customized &os; installation media can be created by
building a custom release. Follow the instructions in the
<link
xlink:href="&url.articles.releng;/article.html">Release
Engineering</link> article.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="windows-coexist">
<para>Can &windows; co-exist with &os;?</para>
</question>
<answer>
<para>If &windows; is installed first, then yes. &os;'s
boot manager will then manage to boot &windows; and &os;.
If &windows; is installed afterwards, it will
overwrite the boot manager. If that
happens, see the next section.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="bootmanager-restore">
<para>Another operating system destroyed my Boot Manager.
How do I get it back?</para>
</question>
<answer>
<para>This depends upon the boot manager.
The &os; boot selection menu can be reinstalled using
&man.boot0cfg.8;. For example, to restore the boot menu
onto the disk <replaceable>ada0</replaceable>:</para>
<screen>&prompt.root; <userinput>boot0cfg -B ada0</userinput></screen>
<para>The non-interactive MBR bootloader can be installed
using &man.gpart.8;:</para>
<screen>&prompt.root; <userinput>gpart bootcode -b /boot/mbr ada0</userinput></screen>
<para>For more complex situations, including GPT disks, see
&man.gpart.8;.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="need-complete-sources">
<para>Do I need to install the source?</para>
</question>
<answer>
<para>In general, no. There is nothing in the base system
which requires the presence of the source to operate.
Some ports, like <package>sysutils/lsof</package>, will
not build unless the source is installed. In particular,
if the port builds a kernel module or directly operates on
kernel structures, the source must be installed.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="need-kernel">
<para>Do I need to build a kernel?</para>
</question>
<answer>
<para>Usually not. The supplied <literal>GENERIC</literal>
kernel contains the drivers an ordinary computer will
need. &man.freebsd-update.8;, the &os; binary upgrade
tool, cannot upgrade custom kernels, another reason to
stick with the <literal>GENERIC</literal> kernel when
possible. For computers with very limited RAM, such as
embedded systems, it may be worthwhile to build a smaller
custom kernel containing just the required drivers.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="password-encryption">
<para>Should I use DES, Blowfish, or MD5 passwords and how
do I specify which form my users receive?</para>
</question>
<answer>
<para>&os; uses
<emphasis>SHA512</emphasis> by
default. DES
passwords are still available for backwards compatibility
with operating systems that still
use the less secure password format. &os; also supports
the Blowfish and MD5 password formats. Which
password format to use for new passwords is controlled by
the <literal>passwd_format</literal> login capability in
<filename>/etc/login.conf</filename>, which takes values
of <literal>des</literal>, <literal>blf</literal> (if
these are available) or <literal>md5</literal>. See the
&man.login.conf.5; manual page for more information about
login capabilities.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ffs-limits">
<para>What are the limits for FFS file systems?</para>
</question>
<answer>
<para>For FFS file systems, the largest file system is
practically limited by the amount of memory required to
&man.fsck.8; the file system. &man.fsck.8; requires one
bit per fragment, which with the default fragment size of
4&nbsp;KB equates to 32&nbsp;MB of memory per TB of disk.
This does mean that on architectures which limit userland
processes to 2&nbsp;GB (e.g., &i386;), the maximum
&man.fsck.8;'able filesystem is ~60&nbsp;TB.</para>
<para>If there was not a &man.fsck.8; memory limit the
maximum filesystem size would be 2&nbsp;^&nbsp;64 (blocks)
* 32&nbsp;KB => 16 Exa * 32&nbsp;KB => 512
ZettaBytes.</para>
<para>The maximum size of a single FFS file is approximately
2&nbsp;PB with the default block size of 32&nbsp;KB. Each
32&nbsp;KB block can point to 4096 blocks. With triple
indirect blocks, the calculation is 32&nbsp;KB * 12 +
32&nbsp;KB * 4096 + 32&nbsp;KB * 4096^2 + 32&nbsp;KB *
4096^3. Increasing the block size to 64&nbsp;KB will
increase the max file size by a factor of 16.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="archsw-readin-failed-error">
<para>Why do I get an error message, <errorname>readin
failed</errorname> after compiling and booting a new
kernel?</para>
</question>
<answer>
<para>The world and kernel are out of sync. This
is not supported. Be sure to use <command>make
buildworld</command> and <command>make
buildkernel</command> to update the kernel.</para>
<para>Boot the system by specifying the kernel directly at
the second stage, pressing any key when the
<literal>|</literal> shows up before loader is
started.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="general-configuration-tool">
<para>Is there a tool to perform post-installation
configuration tasks?</para>
</question>
<answer>
<para>Yes. <application>bsdconfig</application> provides a
nice interface to configure &os; post-installation.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="hardware">
<title>Hardware Compatibility</title>
<sect1 xml:id="compatibility-general">
<title>General</title>
<qandaset>
<qandaentry>
<question xml:id="which-hardware-to-get">
<para>I want to get a piece of hardware for my &os;
system. Which model/brand/type is best?</para>
</question>
<answer>
<para>This is discussed continually on the &os; mailing
lists but is to be expected since hardware changes so
quickly. Read through the Hardware&nbsp;Notes
for &os; <link
xlink:href="&rel.current.hardware;">&rel.current;</link>
or <link
xlink:href="&rel2.current.hardware;">&rel2.current;</link>
and search the mailing list <link
xlink:href="https://www.FreeBSD.org/search/#mailinglists">archives</link>
before asking about the latest and greatest hardware.
Chances are a discussion about that type of hardware
took place just last week.</para>
<para>Before purchasing a laptop, check the archives for
&a.mobile; and &a.questions;, or possibly a specific
mailing list for a particular hardware type.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="memory-upper-limitation">
<para>What are the limits for memory? Does &os; support
more than 4&nbsp;GB of memory
(RAM)? More than 16&nbsp;GB? More than
48&nbsp;GB?</para>
</question>
<answer>
<para>&os; as an operating system generally supports
as much physical memory (RAM) as the platform it is
running on does. Keep in mind that different platforms
have different limits for memory; for example &i386;
without <acronym>PAE</acronym> supports at most
4&nbsp;GB of memory (and usually less than that because
of PCI address space) and &i386; with PAE supports at
most 64&nbsp;GB memory. As of &os;&nbsp;10, AMD64
platforms support up to 4&nbsp;TB of physical
memory.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="memory-i386-over-4gb">
<para>Why does &os; report less than 4&nbsp;GB memory when
installed on an &i386; machine?</para>
</question>
<answer>
<para>The total address space on &i386; machines is
32-bit, meaning that at most 4&nbsp;GB of memory is
addressable (can be accessed). Furthermore, some
addresses in this range are reserved by hardware for
different purposes, for example for using and
controlling PCI devices, for accessing video memory, and
so on. Therefore, the total amount of memory usable by
the operating system for its kernel and applications is
limited to significantly less than 4&nbsp;GB. Usually,
3.2&nbsp;GB to 3.7&nbsp;GB is the maximum usable
physical memory in this configuration.</para>
<para>To access more than 3.2&nbsp;GB to 3.7&nbsp;GB of
installed memory (meaning up to 4&nbsp;GB but also more
than 4&nbsp;GB), a special tweak called
<acronym>PAE</acronym> must be used. PAE stands for
Physical Address Extension and is a way for 32-bit x86
CPUs to address more than 4&nbsp;GB of memory. It
remaps the memory that would otherwise be overlaid by
address reservations for hardware devices above the
4&nbsp;GB range and uses it as additional physical
memory (see &man.pae.4;). Using PAE has some drawbacks;
this mode of memory access is a little bit slower than
the normal (without PAE) mode and loadable modules (see
&man.kld.4;) are not supported. This means all drivers
must be compiled into the kernel.</para>
<para>The most common way to enable PAE is to build a new
kernel with the special ready-provided kernel
configuration file called <filename>PAE</filename>,
which is already configured to build a safe kernel.
Note that some entries in this kernel configuration file
are too conservative and some drivers marked as unready
to be used with PAE are actually usable. A rule of
thumb is that if the driver is usable on 64-bit
architectures (like AMD64), it is also usable with PAE.
When creating a custom kernel configuration
file, PAE can be enabled by adding the following
line:</para>
<programlisting>options PAE</programlisting>
<para>PAE is not much used nowadays because most new x86
hardware also supports running in 64-bit mode, known as
AMD64 or &intel;&nbsp;64. It has a much larger address
space and does not need such tweaks. &os; supports
AMD64 and it is recommended that this version of &os; be
used instead of the &i386; version if 4&nbsp;GB or more
memory is required.</para>
</answer>
</qandaentry>
</qandaset>
</sect1>
<sect1 xml:id="compatibility-processors">
<title>Architectures and Processors</title>
<qandaset>
<qandaentry>
<question xml:id="architectures">
<para>Does &os; support architectures other than the
x86?</para>
</question>
<answer>
<para>Yes. &os; divides support into multiple tiers.
Tier 1 architectures, such as i386 or amd64; are fully
supported. Tiers 2 and 3 are supported on a
best-effort basis. A full explanation of the tier
system is available in the <link
xlink:href="&url.articles.committers-guide;/archs.html">Committer's
Guide.</link></para>
<para>A complete list of supported architectures can be
found on the <link
xlink:href="https://www.FreeBSD.org/platforms/">platforms
page.</link></para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="smp-support">
<para>Does &os; support Symmetric Multiprocessing
(SMP)?</para>
</question>
<answer>
<para>&os; supports symmetric multi-processor (SMP) on all
non-embedded platforms (e.g, &arch.i386;, &arch.amd64;,
etc.). SMP is also supported in arm and MIPS kernels,
although some CPUs may not support this. &os;'s SMP
implementation uses fine-grained locking, and
performance scales nearly linearly with number of
CPUs.</para>
<para>&man.smp.4; has more details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="microcode">
<para>What is microcode?
How do I install &intel; CPU microcode updates?</para>
</question>
<answer>
<para>Microcode is a method of programmatically
implementing hardware level instructions. This allows
for CPU bugs to be fixed without replacing the on board
chip.</para>
<para>Install <package>sysutils/devcpu-data</package>,
then add:</para>
<programlisting>microcode_update_enable="YES"</programlisting>
<para>to <filename>/etc/rc.conf</filename></para>
</answer>
</qandaentry>
</qandaset>
</sect1>
<sect1 xml:id="compatibility-drives">
<title>Hard Drives, Tape Drives, and CD and DVD Drives</title>
<qandaset>
<qandaentry>
<question xml:id="supported-hard-drives">
<para>What kind of hard drives does &os; support?</para>
</question>
<answer>
<para>&os; supports EIDE, SATA, SCSI, and SAS drives (with
a compatible controller; see the next section), and all
drives using the original <quote>Western Digital</quote>
interface (MFM, RLL, ESDI, and of course IDE). A few
ESDI controllers that use proprietary interfaces may not
work: stick to WD1002/3/6/7 interfaces and
clones.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="supported-scsi-controllers">
<para>Which SCSI or SAS controllers are supported?</para>
</question>
<answer>
<para>See the complete list in the Hardware Notes for &os;
<link
xlink:href="&rel.current.hardware;">&rel.current;</link>
or <link
xlink:href="&rel2.current.hardware;">&rel2.current;</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="tape-support">
<para>What types of tape drives are supported?</para>
</question>
<answer>
<para>&os; supports all standard SCSI tape
interfaces.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="tape-changer-support">
<para>Does &os; support tape changers?</para>
</question>
<answer>
<para>&os; supports SCSI changers using the &man.ch.4;
device and the &man.chio.1; command. The details of how
to control the changer can be found in
&man.chio.1;.</para>
<para>While
<application>AMANDA</application> and some other
products already understands changers, other
applications only know how to move a tape from one point
to another. In this case, keep track of which slot a
tape is in and which slot the tape currently in the
drive needs to go back to.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="supported-cdrom-drives">
<para>Which CD-ROM and CD-RW drives are supported by
&os;?</para>
</question>
<answer>
<para>Any SCSI drive connected to a supported controller
is supported. Most ATAPI compatible IDE CD-ROMs are
supported.</para>
<para>&os; supports any ATAPI-compatible IDE CD-R or CD-RW
drive.</para>
<para>&os; also supports any SCSI CD-R or CD-RW drives.
Install the <package>sysutils/cdrtools</package> port or
package, then use <command>cdrecord</command>.</para>
</answer>
</qandaentry>
</qandaset>
</sect1>
<sect1 xml:id="compatibility-kbd-mice">
<title>Keyboards and Mice</title>
<qandaset>
<qandaentry>
<question xml:id="moused">
<para>Is it possible to use a mouse outside the
X Window system?</para>
</question>
<answer>
<para>The default console driver,
&man.syscons.4;, provides the ability to use a mouse
pointer in text consoles to cut &amp; paste text. Run
the mouse daemon, &man.moused.8;, and turn on the mouse
pointer in the virtual console:</para>
<screen>&prompt.root; <userinput>moused -p /dev/xxxx -t yyyy</userinput>
&prompt.root; <userinput>vidcontrol -m on</userinput></screen>
<para>Where <replaceable>xxxx</replaceable> is the mouse
device name and <replaceable>yyyy</replaceable> is a
protocol type for the mouse. The mouse daemon can
automatically determine the protocol type of most mice,
except old serial mice. Specify the
<literal>auto</literal> protocol to invoke automatic
detection. If automatic detection does not work, see
the &man.moused.8; manual page for a list of supported
protocol types.</para>
<para>For a PS/2 mouse, add
<literal>moused_enable="YES"</literal> to
<filename>/etc/rc.conf</filename> to start the mouse
daemon at boot time. Additionally, to
use the mouse daemon on all virtual terminals instead of
just the console, add <literal>allscreens_flags="-m
on"</literal> to
<filename>/etc/rc.conf</filename>.</para>
<para>When the mouse daemon is running, access to the
mouse must be coordinated between the mouse daemon and
other programs such as X Windows. Refer to the
<acronym>FAQ</acronym>
<link linkend="x-and-moused">Why does my mouse not work
with X?</link> for more details on this issue.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="text-mode-cut-paste">
<para>How do I cut and paste text with a mouse in the text
console?</para>
</question>
<answer>
<para>It is not possible to remove data using the mouse.
However, it is possible to copy and paste. Once the
mouse daemon is running as described in the <link
linkend="moused">previous question</link>, hold down
button 1 (left button) and move the mouse to select a
region of text. Then, press button 2 (middle button) to
paste it at the text cursor. Pressing button 3 (right
button) will <quote>extend</quote> the selected region
of text.</para>
<para>If the mouse does not have a middle button, it is
possible to emulate one or remap buttons using mouse
daemon options. See the &man.moused.8; manual page for
details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mouse-wheel-buttons">
<para>My mouse has a fancy wheel and buttons. Can I use
them in &os;?</para>
</question>
<answer>
<para>The answer is, unfortunately, <quote>It
depends</quote>. These mice with additional features
require specialized driver in most cases. Unless the
mouse device driver or the user program has specific
support for the mouse, it will act just like a standard
two, or three button mouse.</para>
<para>For the possible usage of wheels in the X Window
environment, refer to <link
linkend="x-and-wheel">that section</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="keyboard-delete-key">
<para>How do I use my delete key in <command>sh</command>
and <command>csh</command>?</para>
</question>
<answer>
<para>For the <application>Bourne Shell</application>, add
the following lines to <filename>~/.shrc</filename>.
See &man.sh.1; and &man.editrc.5;.</para>
<programlisting>bind ^? ed-delete-next-char # for console
bind ^[[3~ ed-delete-next-char # for xterm</programlisting>
<para>For the <application>C Shell</application>, add the
following lines to <filename>~/.cshrc</filename>.
See &man.csh.1;.</para>
<programlisting>bindkey ^? delete-char # for console
bindkey ^[[3~ delete-char # for xterm</programlisting>
<para>For more information, see <link
xlink:href="http://www.ibb.net/~anne/keyboard.html">this
page</link>.</para>
</answer>
</qandaentry>
</qandaset>
</sect1>
<sect1 xml:id="compatibility-other">
<title>Other Hardware</title>
<qandaset>
<qandaentry>
<question xml:id="es1370-silent-pcm">
<para>Workarounds for no sound from my &man.pcm.4; sound
card?</para>
</question>
<answer>
<para>Some sound cards set their output volume to 0 at
every boot. Run the following command every time the
machine boots:</para>
<screen>&prompt.root; <userinput>mixer pcm 100 vol 100 cd 100</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="power-management-support">
<para>Does &os; support power management on my
laptop?</para>
</question>
<answer>
<para>&os; supports the <acronym>ACPI</acronym> features
found in modern hardware. Further information can be
found in &man.acpi.4;.</para>
</answer>
</qandaentry>
</qandaset>
</sect1>
</chapter>
<chapter xml:id="troubleshoot">
<title>Troubleshooting</title>
<qandaset>
<qandaentry>
<question xml:id="pae">
<para>Why is &os; finding the wrong amount of memory on
&i386; hardware?</para>
</question>
<answer>
<para>The most likely reason is the difference between
physical memory addresses and virtual addresses.</para>
<para>The convention for most PC hardware is to use the
memory area between 3.5&nbsp;GB and 4&nbsp;GB for a
special purpose (usually for PCI). This address space is
used to access PCI hardware. As a result real, physical
memory cannot be accessed by that address space.</para>
<para>What happens to the memory that should appear in that
location is hardware dependent. Unfortunately,
some hardware does nothing and the ability to use that
last 500&nbsp;MB of RAM is entirely lost.</para>
<para>Luckily, most hardware remaps the memory to a higher
location so that it can still be used. However, this can
cause some confusion when watching the boot
messages.</para>
<para>On a 32-bit version of &os;, the memory appears lost,
since it will be remapped above 4&nbsp;GB, which a 32-bit
kernel is unable to access. In this case, the solution is
to build a PAE enabled kernel. See the entry on memory
limits for more information.</para>
<para>On a 64-bit version of &os;, or when running a
PAE-enabled kernel, &os; will correctly detect and remap
the memory so it is usable. During boot, however, it may
seem as if &os; is detecting more memory than the system
really has, due to the described remapping. This is
normal and the available memory will be corrected as the
boot process completes.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="signal11">
<para>Why do my programs occasionally die with
<errorname>Signal 11</errorname> errors?</para>
</question>
<answer>
<para>Signal 11 errors are caused when a process has
attempted to access memory which the operating system has
not granted it access to. If something like this is
happening at seemingly random intervals,
start investigating the cause.</para>
<para>These problems can usually be attributed to
either:</para>
<orderedlist>
<listitem>
<para>If the problem is occurring only in a specific
custom application, it is
probably a bug in the code.</para>
</listitem>
<listitem>
<para>If it is a problem with part of the base &os;
system, it may also be buggy code, but more often than
not these problems are found and fixed long before us
general <acronym>FAQ</acronym> readers get to use
these bits of code (that is what -CURRENT is
for).</para>
</listitem>
</orderedlist>
<para>It is probably
not a &os; bug if the
problem occurs compiling a program, but the activity
that the compiler is carrying out changes each
time.</para>
<para>For example, if <command>make
buildworld</command> fails while trying
to compile <filename>ls.c</filename> into
<filename>ls.o</filename> and, when run again, it fails
in the same place, this is a broken build. Try
updating source and try again. If the compile fails
elsewhere, it is almost certainly due to hardware.</para>
<para>In the first case, use a debugger such as
&man.gdb.1; to find the point in the program which is
attempting to access a bogus address and fix
it.</para>
<para>In the second case, verify which piece of
hardware is at fault.</para>
<para>Common causes of this include:</para>
<orderedlist>
<listitem>
<para>The hard disks might be overheating: Check that
the fans are still working, as the disk and
other hardware might be overheating.</para>
</listitem>
<listitem>
<para>The processor running is overheating: This might
be because the processor has been overclocked, or the
fan on the processor might have died. In either case,
ensure that the hardware is running at
what it is specified to run at, at least while trying
to solve this problem. If it is not, clock it back
to the default settings.)</para>
<para>Regarding overclocking, it is far
cheaper to have a slow system than a fried system that
needs replacing! Also the community is not
sympathetic to problems on overclocked systems.</para>
</listitem>
<listitem>
<para>Dodgy memory: if multiple memory
SIMMS/DIMMS are installed, pull them all out and try
running the machine with each SIMM or DIMM
individually to narrow the problem down to either the
problematic DIMM/SIMM or perhaps even a
combination.</para>
</listitem>
<listitem>
<para>Over-optimistic motherboard settings: the BIOS
settings, and some motherboard jumpers, provide
options to set various timings. The defaults
are often sufficient, but sometimes setting the wait
states on RAM too low, or setting the <quote>RAM
Speed: Turbo</quote> option
will cause strange behavior. A possible idea is to
set to BIOS defaults, after noting
the current settings first.</para>
</listitem>
<listitem>
<para>Unclean or insufficient power to the motherboard.
Remove any unused I/O boards, hard disks, or
CD-ROMs,
or disconnect the power cable from them, to see if
the power supply can manage a smaller load. Or try
another power supply, preferably one with a little
more power. For instance, if the current power supply
is rated at 250&nbsp;Watts, try one rated at
300&nbsp;Watts.</para>
</listitem>
</orderedlist>
<para>Read the section on
<link linkend="signal11">Signal 11</link> for a further
explanation and a discussion on how memory testing
software or hardware can still pass faulty memory. There
is an extensive <acronym>FAQ</acronym> on this at <link
xlink:href="http://www.bitwizard.nl/sig11/">the SIG11
problem <acronym>FAQ</acronym></link>.</para>
<para>Finally, if none of this has helped, it is possibly
a bug in &os;.
Follow <link linkend="access-pr">these instructions</link>
to send a problem report.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="trap-12-panic">
<para>My system crashes with either <errorname>Fatal trap
12: page fault in kernel mode</errorname>, or
<errorname>panic:</errorname>, and spits out a bunch of
information. What should I do?</para>
</question>
<answer>
<para>The &os; developers are interested in these
errors, but need more information than just the error
message. Copy the full crash message. Then consult the
<acronym>FAQ</acronym> section on <link
linkend="kernel-panic-troubleshooting">kernel
panics</link>, build a debugging kernel, and get a
backtrace. This might sound difficult, but does not
require any programming skills. Just follow the
instructions.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="proc-table-full">
<para>What is the meaning of the error <errorname>maxproc
limit exceeded by uid %i, please see tuning(7) and
login.conf(5)</errorname>?</para>
</question>
<answer>
<para>The &os; kernel will only allow a certain number of
processes to exist at one time. The number is based on
the <varname>kern.maxusers</varname> &man.sysctl.8;
variable. <varname>kern.maxusers</varname> also affects
various other in-kernel limits, such as network buffers.
If the machine is heavily loaded,
increase <varname>kern.maxusers</varname>. This will
increase these other system limits in addition to the
maximum number of processes.</para>
<para>To adjust the <varname>kern.maxusers</varname> value,
see the <link
xlink:href="&url.books.handbook;/configtuning-kernel-limits.html#kern-maxfiles">File/Process
Limits</link> section of the Handbook. While that
section refers to open files, the same limits apply to
processes.</para>
<para>If the machine is lightly loaded but running a very
large number of processes, adjust the
<varname>kern.maxproc</varname> tunable by defining it in
<filename>/boot/loader.conf</filename>. The tunable will
not get adjusted until the system is rebooted. For more
information about tuning tunables, see
&man.loader.conf.5;. If these processes are being run by
a single user, adjust
<varname>kern.maxprocperuid</varname> to be one less than
the new <varname>kern.maxproc</varname> value. It must
be at least one less because one system program,
&man.init.8;, must always be running.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="remote-fullscreen">
<para>Why do full screen applications on remote machines
misbehave?</para>
</question>
<answer>
<para>The remote machine may be setting the terminal type to
something other than <literal>xterm</literal> which is
required by the &os; console. Alternatively the kernel
may have the wrong values for the width and height of the
terminal.</para>
<para>Check the value of the <envar>TERM</envar>
environment variable is <literal>xterm</literal>. If the
remote machine does not support that try
<literal>vt100</literal>.</para>
<para>Run <command>stty -a</command> to check what the
kernel thinks the terminal dimensions are. If they are
incorrect, they can be changed by running
<command>stty rows <replaceable>RR</replaceable> cols
<replaceable>CC</replaceable></command>.</para>
<para>Alternatively, if the client machine has
<package>x11/xterm</package> installed, then running
<command>resize</command> will query the terminal for the
correct dimensions and set them.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="connection-delay">
<para>Why does it take so long to connect to my computer via
<command>ssh</command> or
<command>telnet</command>?</para>
</question>
<answer>
<para>The symptom: there is a long delay between the time
the TCP connection is established and the time when the
client software asks for a password (or, in
&man.telnet.1;'s case, when a login prompt
appears).</para>
<para>The problem: more likely than not, the delay is caused
by the server software trying to resolve the client's IP
address into a hostname. Many servers, including the
<application>Telnet</application> and
<application>SSH</application> servers that come with
&os;, do this to store the hostname in a log file for
future reference by the administrator.</para>
<para>The remedy: if the problem occurs whenever connecting
the client computer to any server, the problem
is with the client. If the problem only occurs
when someone connects to the server computer, the
problem is with the server.</para>
<para>If the problem is with the client, the only remedy is
to fix the DNS so the server can resolve it. If this is
on a local network, consider it a server problem and keep
reading. If this is on the Internet,
contact your ISP.</para>
<para>If the problem is with the server on a
local network, configure the server
to resolve address-to-hostname queries for the local
address range. See &man.hosts.5; and &man.named.8;
for more information. If this is on the
Internet, the problem may be that the local server's
resolver is not functioning correctly. To check, try to
look up another host such as
<systemitem>www.yahoo.com</systemitem>. If it does not
work, that is the problem.</para>
<para>Following a fresh install of &os;, it is also possible
that domain and name server information is missing from
<filename>/etc/resolv.conf</filename>. This will often
cause a delay in <application>SSH</application>, as the
option <literal>UseDNS</literal> is set to
<literal>yes</literal> by default in
<filename>/etc/ssh/sshd_config</filename>. If this is
causing the problem, either fill in the
missing information in
<filename>/etc/resolv.conf</filename> or set
<literal>UseDNS</literal> to <literal>no</literal> in
<filename>sshd_config</filename> as a temporary
workaround.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="file-table-full">
<para>Why does <errorname>file: table is full</errorname>
show up repeatedly in &man.dmesg.8;?</para>
</question>
<answer>
<para>This error message indicates that the number of
available file descriptors have been exhausted on the
system. Refer to the <link
xlink:href="&url.books.handbook;/configtuning-kernel-limits.html#kern-maxfiles">kern.maxfiles</link>
section of the <link
xlink:href="&url.books.handbook;/configtuning-kernel-limits.html">Tuning
Kernel Limits</link> section of the Handbook for a
discussion and solution.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="computer-clock-skew">
<para>Why does the clock on my computer keep incorrect
time?</para>
</question>
<answer>
<para>The computer has two or more clocks, and &os; has
chosen to use the wrong one.</para>
<para>Run &man.dmesg.8;, and check for lines that contain
<literal>Timecounter</literal>. The one with the highest
quality value that &os; chose.</para>
<screen>&prompt.root; <userinput>dmesg | grep Timecounter</userinput>
Timecounter "i8254" frequency 1193182 Hz quality 0
Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
Timecounter "TSC" frequency 2998570050 Hz quality 800
Timecounters tick every 1.000 msec</screen>
<para>Confirm this by checking the
<varname>kern.timecounter.hardware</varname>
&man.sysctl.3;.</para>
<screen>&prompt.root; <userinput>sysctl kern.timecounter.hardware</userinput>
kern.timecounter.hardware: ACPI-fast</screen>
<para>It may be a broken ACPI timer. The simplest solution
is to disable the ACPI timer in
<filename>/boot/loader.conf</filename>:</para>
<programlisting>debug.acpi.disabled="timer"</programlisting>
<para>Or the BIOS may modify the TSC clock&mdash;perhaps to
change the speed of the processor when running from
batteries, or going into a power saving mode, but &os; is
unaware of these adjustments, and appears to gain or lose
time.</para>
<para>In this example, the <literal>i8254</literal> clock is
also available, and can be selected by writing its name to
the <varname>kern.timecounter.hardware</varname>
&man.sysctl.3;.</para>
<screen>&prompt.root; <userinput>sysctl kern.timecounter.hardware=i8254</userinput>
kern.timecounter.hardware: TSC -&gt; i8254</screen>
<para>The computer should now start keeping more accurate
time.</para>
<para>To have this change automatically run at boot time,
add the following line to
<filename>/etc/sysctl.conf</filename>:</para>
<programlisting>kern.timecounter.hardware=i8254</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="indefinite-wait-buffer">
<para>What does the error <errorname>swap_pager: indefinite
wait buffer:</errorname> mean?</para>
</question>
<answer>
<para>This means that a process is trying to page memory
from
disk, and the page attempt has hung trying to access the
disk for more than 20 seconds. It might be caused by bad
blocks on the disk drive, disk wiring, cables, or any
other disk I/O-related hardware. If the drive itself is
bad, disk errors will appear in
<filename>/var/log/messages</filename> and in the output
of <command>dmesg</command>. Otherwise, check the cables
and connections.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="lock-order-reversal">
<para>What is a <errorname>lock order
reversal</errorname>?</para>
</question>
<answer>
<para>The &os; kernel uses a number of resource locks to
arbitrate contention for certain resources. When multiple
kernel threads try to obtain multiple resource locks,
there's always the potential for a deadlock, where two
threads have each obtained one of the locks and blocks
forever waiting for the other thread to release one of the
other locks. This sort of locking problem can be avoided
if all threads obtain the locks in the same order.</para>
<para>A run-time lock diagnostic system called
&man.witness.4;, enabled in &os.current; and disabled by
default for stable branches and releases, detects the
potential for deadlocks due to locking errors, including
errors caused by obtaining multiple resource locks with a
different order from different parts of the kernel. The
&man.witness.4; framework tries to detect this problem as
it happens, and reports it by printing a message to the
system console about a <errorname>lock order
reversal</errorname> (often referred to also as
<acronym>LOR</acronym>).</para>
<para>It is possible to get false positives, as
&man.witness.4; is conservative. A true positive report
<emphasis>does not</emphasis> mean that a system is
dead-locked; instead it should be understood as a warning
that a deadlock could have happened here.</para>
<note>
<para>Problematic <acronym>LOR</acronym>s tend to get
fixed quickly, so check the &a.current; before posting
to it.</para>
</note>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="called-with-non-sleepable-locks-held">
<para>What does <errorname>Called ... with the following
non-sleepable locks held</errorname> mean?</para>
</question>
<answer>
<para>This means that a function that may sleep was called
while a mutex (or other unsleepable) lock was held.</para>
<para>The reason this is an error is because mutexes are not
intended to be held for long periods of time; they are
supposed to only be held to maintain short periods of
synchronization. This programming contract allows device
drivers to use mutexes to synchronize with the rest of the
kernel during interrupts. Interrupts (under &os;) may not
sleep. Hence it is imperative that no subsystem in the
kernel block for an extended period while holding a
mutex.</para>
<para>To catch such errors, assertions may be added to the
kernel that interact with the &man.witness.4; subsystem to
emit a warning or fatal error (depending on the system
configuration) when a potentially blocking call is made
while holding a mutex.</para>
<para>In summary, such warnings are non-fatal, however with
unfortunate timing they could cause undesirable effects
ranging from a minor blip in the system's responsiveness
to a complete system lockup.</para>
<para>For additional information about locking in &os; see
&man.locking.9;.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="touch-not-found">
<para>Why does
<buildtarget>buildworld</buildtarget>/<buildtarget>installworld</buildtarget>
die with the message <errorname>touch: not
found</errorname>?</para>
</question>
<answer>
<para>This error does not mean that the &man.touch.1;
utility is missing. The error is instead probably due to
the dates of the files being set sometime in the future.
If the CMOS clock is set to local time, run
<command>adjkerntz&nbsp;-i</command> to adjust
the kernel clock when booting into single-user
mode.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="applications">
<title>User Applications</title>
<qandaset>
<qandaentry>
<question xml:id="user-apps">
<para>Where are all the user applications?</para>
</question>
<answer>
<para>Refer to <link
xlink:href="&url.base;/ports/index.html">the ports
page</link> for info on software packages ported to
&os;. The list currently tops &os.numports; and is
growing daily, so come back to check often or subscribe to
the &a.announce; for periodic updates on new
entries.</para>
<para>Most ports should work on all supported versions of
&os;. Those that do not are specifically marked as such.
Each time a &os; release is made, a snapshot of the ports
tree at the time of release in also included in the
<filename>ports/</filename> directory.</para>
<para>&os; supports compressed binary packages to easily
install and uninstall ports. Use &man.pkg.7; to control
the installation of packages.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="how-do-download-ports-tree">
<para>How do I download the Ports tree? Should I be using
SVN?</para>
</question>
<answer>
<para>Any of the methods listed here work:</para>
<itemizedlist>
<listitem>
<para>Use portsnap for most use cases. Refer to <link
xlink:href="&url.books.handbook;/ports-using.html">Using
the Ports Collection</link> for instructions on how to
use this tool.</para>
</listitem>
<listitem>
<para>Use SVN if custom patches to the
ports tree are needed. Refer to <link
xlink:href="&url.books.handbook;/svn.html">Using
Subversion</link> for details.</para>
</listitem>
</itemizedlist>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="java">
<para>Does &os; support &java;?</para>
</question>
<answer>
<para>Yes. Refer to <link
xlink:href="&url.base;/java/index.html">https://www.FreeBSD.org/java/</link>
for more information.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ports-4x">
<para>Why can I not build this port on my
&rel2.relx;&nbsp;-, or
&rel.relx;&nbsp;-STABLE machine?</para>
</question>
<answer>
<para>If the installed &os; version lags
significantly behind <emphasis>-CURRENT</emphasis> or
<emphasis>-STABLE</emphasis>, update the
Ports Collection using the instructions in <link
xlink:href="&url.books.handbook;/ports-using.html">Using
the Ports Collection</link>. If the system is
up-to-date, someone might have committed a change to the
port which works for <emphasis>-CURRENT</emphasis> but
which broke the port for <emphasis>-STABLE</emphasis>.
<link xlink:href="https://bugs.FreeBSD.org/submit/">Submit</link>
a bug report, since the Ports Collection is supposed to
work
for both the <emphasis>-CURRENT</emphasis> and
<emphasis>-STABLE</emphasis> branches.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="make-index">
<para>I just tried to build <filename>INDEX</filename> using
<command>make index</command>, and it failed. Why?</para>
</question>
<answer>
<para>First, make sure that the Ports Collection is
up-to-date. Errors that affect building
<filename>INDEX</filename> from an up-to-date copy of the
Ports Collection are high-visibility and are thus almost
always fixed immediately.</para>
<para>There are rare cases where <filename>INDEX</filename>
will not build due to odd cases involving
<varname>OPTIONS_SET</varname>
being set in <filename>make.conf</filename>. If
you suspect that this is the case, try to make
<filename>INDEX</filename> with those variables
turned off before reporting it to &a.ports;.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ports-update">
<para>I updated the sources, now how do I update my
installed ports?</para>
</question>
<answer>
<para>&os; does not include a port upgrading tool, but it
does have some tools to make the upgrade process somewhat
easier. Additional tools are available to simplify
port handling and are described the <link
xlink:href="&url.books.handbook;/ports-using.html">Upgrading
Ports</link> section in the &os; Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ports-major-upgrade">
<para>Do I need to recompile every port each time I perform
a major version update?</para>
</question>
<answer>
<para>Yes! While a recent system will run with
software compiled under an older release,
things will randomly crash and fail to work once
other ports are installed or updated.</para>
<para>When the system is upgraded, various shared libraries,
loadable modules, and other parts of the system will be
replaced with newer versions. Applications linked against
the older versions may fail to start or, in other cases,
fail to function properly.</para>
<para>For more information, see <link
xlink:href="&url.books.handbook;/updating-upgrading-freebsdupdate.html#freebsdupdate-upgrade">the
section on upgrades</link> in the &os; Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ports-minor-upgrade">
<para>Do I need to recompile every port each time I perform
a minor version update?</para>
</question>
<answer>
<para>In general, no. &os; developers do their utmost to
guarantee binary compatibility across all releases with
the same major version number. Any exceptions will be
documented in the Release Notes, and advice given there
should be followed.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="minimal-sh">
<para>Why is <command>/bin/sh</command> so minimal? Why
does &os; not use <command>bash</command> or another
shell?</para>
</question>
<answer>
<para>Many people need to write shell scripts which will be
portable across many systems. That is why &posix;
specifies the shell and utility commands in great detail.
Most scripts are written in Bourne shell (&man.sh.1;), and
because several important programming interfaces
(&man.make.1;, &man.system.3;, &man.popen.3;, and
analogues in higher-level scripting languages like Perl
and Tcl) are specified to use the Bourne shell to
interpret commands. Because the Bourne shell is so often
and widely used, it is important for it to be quick to
start, be deterministic in its behavior, and have a small
memory footprint.</para>
<para>The existing implementation is our best effort at
meeting as many of these requirements simultaneously as we
can. To keep <command>/bin/sh</command> small, we have
not provided many of the convenience features that other
shells have. That is why other more featureful shells
like <command>bash</command>, <command>scsh</command>,
&man.tcsh.1;, and <command>zsh</command> are available.
Compare the memory utilization of
these shells by looking at the <quote>VSZ</quote> and
<quote>RSS</quote> columns in a <command>ps -u</command>
listing.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="midi-sound-files">
<para>How do I create audio CDs from my MIDI files?</para>
</question>
<answer>
<para>To create audio CDs from MIDI files, first install
<package>audio/timidity++</package> from ports then
install manually the GUS patches set by Eric A. Welsh,
available at <uri
xlink:href="http://alleg.sourceforge.net/digmid.html">http://alleg.sourceforge.net/digmid.html</uri>.
After <application>TiMidity++</application> has been
installed properly, MIDI files may be converted to WAV
files with the following command line:</para>
<screen>&prompt.user; <userinput>timidity -Ow -s 44100 -o /tmp/juke/01.wav 01.mid</userinput></screen>
<para>The WAV files can then be converted to other formats
or burned onto audio CDs, as described in the <link
xlink:href="&url.books.handbook;/creating-cds.html">&os;
Handbook</link>.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="kernelconfig">
<title>Kernel Configuration</title>
<qandaset>
<qandaentry>
<question xml:id="make-kernel">
<para>I would like to customize my kernel. Is it
difficult?</para>
</question>
<answer>
<para>Not at all! Check out the <link
xlink:href="&url.books.handbook;/kernelconfig.html">kernel
config section of the Handbook</link>.</para>
<note>
<para>The new <filename>kernel</filename> will be
installed to the <filename>/boot/kernel</filename>
directory along with its modules, while the old kernel
and its modules will be moved to the
<filename>/boot/kernel.old</filename> directory. If
a mistake is made in the
configuration, simply boot the previous version of the
kernel.</para>
</note>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="why-kernel-big">
<para>Why is my kernel so big?</para>
</question>
<answer>
<para><literal>GENERIC</literal> kernels shipped with &os;
are compiled in <emphasis>debug mode</emphasis>.
Kernels built in debug mode contain debug data in
separate files that are used for debugging.
&os; releases prior to 11.0 store these debug files in
the same directory as the kernel itself,
<filename>/boot/kernel/</filename>.
In &os; 11.0 and later the debug files are stored in
<filename>/usr/lib/debug/boot/kernel/</filename>.
Note that there will be little or no performance loss from
running a debug kernel, and it is useful to keep one
around in case of a system panic.</para>
<para>When running low on disk space, there
are different options to reduce the size of
<filename>/boot/kernel/</filename> and
<filename>/usr/lib/debug/</filename>.</para>
<para>To not install the symbol files,
make sure the following line exists in
<filename>/etc/src.conf</filename>:</para>
<programlisting>WITHOUT_KERNEL_SYMBOLS=yes</programlisting>
<para>For more information see &man.src.conf.5;.</para>
<para>If you want to avoid building debug files altogether,
make sure that both of the following are true:</para>
<itemizedlist>
<listitem>
<para>This line does not exist in the kernel
configuration file:</para>
<programlisting>makeoptions DEBUG=-g</programlisting>
</listitem>
<listitem>
<para>Do not run &man.config.8; with
<option>-g</option>.</para>
</listitem>
</itemizedlist>
<para>Either of the above settings will cause the kernel to
be built in debug mode.</para>
<para>To build and install only the specified modules, list
them in
<filename>/etc/make.conf</filename>:</para>
<programlisting>MODULES_OVERRIDE= <replaceable>accf_http ipfw</replaceable></programlisting>
<para>Replace <emphasis>accf_httpd ipfw</emphasis> with a
list of needed modules. Only the listed modules will be
built. This reduces the size of the kernel
directory and decreases the amount of time needed to
build the kernel. For more information, read
<filename>/usr/share/examples/etc/make.conf</filename>.</para>
<para>Unneeded devices can be removed from the kernel
to further reduce the size. See <xref
linkend="make-kernel"/> for more information.</para>
<para>To put any of these options into effect, follow the
instructions to <link
xlink:href="&url.books.handbook;/kernelconfig-building.html">build
and install</link> the new kernel.</para>
<para>For reference, the &os; 11 &arch.amd64; kernel
(<filename>/boot/kernel/kernel</filename>) is
approximately 25&nbsp;MB.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="generic-kernel-build-failure">
<para>Why does every kernel I try to build fail to compile,
even <filename>GENERIC</filename>?</para>
</question>
<answer>
<para>There are a number of possible causes for this
problem:</para>
<itemizedlist>
<listitem>
<para>The source
tree is different from the one used to build the
currently running system. When attempting an upgrade,
read <filename>/usr/src/UPDATING</filename>, paying
particular attention to the <quote>COMMON
ITEMS</quote> section at the end.</para>
</listitem>
<listitem>
<para>The <command>make
buildkernel</command> command did not complete
successfully. The <command>make
buildkernel</command> target relies on files
generated by the <command>make buildworld</command>
target to complete its job correctly.</para>
</listitem>
<listitem>
<para>Even when building <link
linkend="stable">&os;-STABLE</link>, it is possible
that the source tree was fetched at a time when it was
either being modified or it was broken.
Only releases are guaranteed to be
buildable, although <link
linkend="stable">&os;-STABLE</link> builds fine the
majority of the time. Try re-fetching the source tree
and see if the problem goes away. Try using a
different mirror in case the previous one is having
problems.</para>
</listitem>
</itemizedlist>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="scheduler-in-use">
<para>Which scheduler is in use on a
running system?</para>
</question>
<answer>
<para>The name of the scheduler currently being used is
directly available as the value of the
<varname>kern.sched.name</varname> sysctl:</para>
<screen>&prompt.user; sysctl <replaceable>kern.sched.name</replaceable>
kern.sched.name: ULE</screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="scheduler-kern-quantum">
<para>What is <varname>kern.sched.quantum</varname>?</para>
</question>
<answer>
<para><varname>kern.sched.quantum</varname> is the maximum
number of ticks a process can run without being preempted
in the 4BSD scheduler.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="disks">
<title>Disks, File Systems, and Boot Loaders</title>
<qandaset>
<qandaentry>
<question xml:id="adding-disks">
<para>How can I add my new hard disk to my &os;
system?</para>
</question>
<answer>
<para>See the <link
xlink:href="&url.books.handbook;/disks-adding.html">Adding
Disks</link> section in the &os; Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="new-huge-disk">
<para>How do I move my system over to my huge new
disk?</para>
</question>
<answer>
<para>The best way is to reinstall the operating system on
the new disk, then move the user data over. This is
highly recommended when tracking
<emphasis>-STABLE</emphasis> for more than one release or
when updating a release instead of installing a new one.
Install booteasy on both disks with &man.boot0cfg.8; and
dual boot until you are happy with the new configuration.
Skip the next paragraph to find out how to move the data
after doing this.</para>
<para>Alternatively, partition and label the new disk with
either &man.sade.8; or &man.gpart.8;. If the disks are
MBR-formatted, booteasy can be installed on both disks
with &man.boot0cfg.8; so that the computer can dual boot
to the old or new system after the copying is done.</para>
<para>Once the new disk set up,
the data cannot just be copied. Instead, use tools that
understand device files and system flags, such as
&man.dump.8;. Although it is recommended
to move the data while in single-user mode, it
is not required.</para>
<para>When the disks are formatted with
<acronym>UFS</acronym>, never use anything but
&man.dump.8; and &man.restore.8; to move the root file
system. These commands should also be used when moving a
single partition to another empty partition. The sequence
of steps to use <command>dump</command> to move the data
from one <acronym>UFS</acronym> partitions to a new
partition is:</para>
<procedure>
<step>
<para><command>newfs</command> the new partition.</para>
</step>
<step>
<para><command>mount</command> it on a temporary mount
point.</para>
</step>
<step>
<para><command>cd</command> to that directory.</para>
</step>
<step>
<para><command>dump</command> the old partition, piping
output to the new one.</para>
</step>
</procedure>
<para>For example, to move
<filename>/dev/ada1s1a</filename> with
<filename>/mnt</filename> as the temporary mount point,
type:</para>
<screen>&prompt.root; <userinput>newfs /dev/ada1s1a</userinput>
&prompt.root; <userinput>mount /dev/ada1s1a /mnt</userinput>
&prompt.root; <userinput>cd /mnt</userinput>
&prompt.root; <userinput>dump 0af - / | restore rf -</userinput></screen>
<para>Rearranging partitions with
<command>dump</command> takes a bit more work. To merge a
partition like <filename>/var</filename> into its parent,
create the new partition large enough for both, move the
parent partition as described above, then move the child
partition into the empty directory that the first move
created:</para>
<screen>&prompt.root; <userinput>newfs /dev/ada1s1a</userinput>
&prompt.root; <userinput>mount /dev/ada1s1a /mnt</userinput>
&prompt.root; <userinput>cd /mnt</userinput>
&prompt.root; <userinput>dump 0af - / | restore rf -</userinput>
&prompt.root; <userinput>cd var</userinput>
&prompt.root; <userinput>dump 0af - /var | restore rf -</userinput></screen>
<para>To split a directory from its parent, say putting
<filename>/var</filename> on its own partition when it was
not before, create both partitions, then mount the child
partition on the appropriate directory in the temporary
mount point, then move the old single partition:</para>
<screen>&prompt.root; <userinput>newfs /dev/ada1s1a</userinput>
&prompt.root; <userinput>newfs /dev/ada1s1d</userinput>
&prompt.root; <userinput>mount /dev/ada1s1a /mnt</userinput>
&prompt.root; <userinput>mkdir /mnt/var</userinput>
&prompt.root; <userinput>mount /dev/ada1s1d /mnt/var</userinput>
&prompt.root; <userinput>cd /mnt</userinput>
&prompt.root; <userinput>dump 0af - / | restore rf -</userinput></screen>
<para>The &man.cpio.1; and &man.pax.1; utilities are also
available for moving user data. These are known to lose
file flag information, so use them with caution.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="safe-softupdates">
<para>Which partitions can safely use Soft Updates? I have
heard that Soft Updates on <filename>/</filename> can
cause problems. What about Journaled Soft Updates?</para>
</question>
<answer>
<para>Short answer: Soft Updates can usually be safely used
on all partitions.</para>
<para>Long answer: Soft Updates has two characteristics
that may be undesirable on certain partitions. First, a
Soft Updates partition has a small chance of losing data
during a system crash. The partition will not be
corrupted as the data will simply be lost. Second, Soft
Updates can cause temporary space shortages.</para>
<para>When using Soft Updates, the kernel can take up to
thirty seconds to write changes to the physical disk.
When a large file is deleted the file still resides on
disk until the kernel actually performs the deletion.
This can cause a very simple race condition. Suppose
one large file is deleted and another large file is
immediately created. The first large file is not yet
actually removed from the physical disk, so the disk might
not have enough room for the second large file. This will
produce an error that the partition does not have enough
space, even though a large chunk of space has just been
released. A few seconds later, the file creation works as
expected.</para>
<para>If a system should crash after the kernel accepts a
chunk of data for writing to disk, but before that data is
actually written out, data could be lost. This risk is
extremely small, but generally manageable.</para>
<para>These issues affect all partitions using Soft Updates.
So, what does this mean for the root partition?</para>
<para>Vital information on the root partition changes very
rarely. If the system crashed during the thirty-second
window after such a change is made, it is possible that
data could be lost. This risk is negligible for most
applications, but be aware that it exists. If
the system cannot tolerate this much risk, do not use
Soft Updates on the root file system!</para>
<para><filename>/</filename> is traditionally one of the
smallest partitions. If
<filename>/tmp</filename> is on
<filename>/</filename>, there may be intermittent
space problems. Symlinking <filename>/tmp</filename> to
<filename>/var/tmp</filename> will solve this
problem.</para>
<para>Finally, &man.dump.8; does not work in live mode (-L)
on a filesystem, with Journaled Soft Updates
(<acronym>SU+J</acronym>).</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mount-foreign-fs">
<para>Can I mount other foreign file systems under
&os;?</para>
</question>
<answer>
<para>&os; supports a variety of other file systems.</para>
<variablelist>
<varlistentry>
<term>UFS</term>
<listitem>
<para>UFS CD-ROMs can be mounted directly on &os;.
Mounting disk partitions from Digital UNIX and other
systems that support UFS may be more complex,
depending on the details of the disk partitioning
for the operating system in question.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ext2/ext3</term>
<listitem>
<para>&os; supports <literal>ext2fs</literal> and
<literal>ext3fs</literal> partitions. See
&man.ext2fs.5; for more information.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>NTFS</term>
<listitem>
<para>FUSE based NTFS support is available as a port
(<package>sysutils/fusefs-ntfs</package>). For more
information see <link
xlink:href="http://www.tuxera.com/community/ntfs-3g-manual/"><application>ntfs-3g</application></link>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FAT</term>
<listitem>
<para>&os; includes a read-write FAT driver. For more
information, see &man.mount.msdosfs.8;.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ZFS</term>
<listitem>
<para>&os; includes a port of &sun;'s ZFS driver. The
current recommendation is to use it only on
&arch.amd64; platforms with sufficient memory. For
more information, see &man.zfs.8;.</para>
</listitem>
</varlistentry>
</variablelist>
<para>&os; includes the Network File System
<acronym>NFS</acronym> and the &os; Ports Collection
provides several FUSE applications to support many other
file systems.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mount-dos">
<para>How do I mount a secondary DOS partition?</para>
</question>
<answer>
<para>The secondary DOS partitions are found after
<emphasis>all</emphasis> the primary partitions. For
example, if <literal>E</literal> is the
second DOS partition on the second SCSI drive, there will
be a device file for <quote>slice 5</quote> in
<filename>/dev</filename>. To mount it:</para>
<screen>&prompt.root; <userinput>mount -t msdosfs /dev/da1s5 /dos/e</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="crypto-file-system">
<para>Is there a cryptographic file system for &os;?</para>
</question>
<answer>
<para>Yes, &man.gbde.8; and &man.geli.8;.
See the <link
xlink:href="&url.books.handbook;/disks-encrypting.html">Encrypting
Disk Partitions</link> section of the &os;
Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="grub-loader">
<para>How do I boot &os; and &linux; using
<application>GRUB</application>?</para>
</question>
<answer>
<para>To boot &os; using <application>GRUB</application>,
add the following to either
<filename>/boot/grub/menu.lst</filename> or
<filename>/boot/grub/grub.conf</filename>, depending upon
which is used by the &linux; distribution.</para>
<programlisting>title &os; 9.1
root <replaceable>(hd0,a)</replaceable>
kernel /boot/loader</programlisting>
<para>Where <replaceable>hd0,a</replaceable> points to the
root partition on the first disk. To specify
the slice number, use something like this
<replaceable>(hd0,2,a)</replaceable>. By default, if the
slice number is omitted, <application>GRUB</application>
searches the first slice
which has the <literal>a</literal> partition.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="booteasy-loader">
<para>How do I boot &os; and &linux; using
<application>BootEasy?</application></para>
</question>
<answer>
<para>Install LILO at the start of the &linux; boot
partition instead of in the Master Boot Record. You can
then boot LILO from
<application>BootEasy</application>.</para>
<para>This is recommended when running &windows; and &linux;
as it makes it simpler to get &linux; booting again if
&windows; is reinstalled.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="changing-bootprompt">
<para>How do I change the boot prompt from
<literal>???</literal> to something more
meaningful?</para>
</question>
<answer>
<para>This cannot be accomplished with the standard boot
manager without rewriting it. There are a number of other
boot managers in the <filename>sysutils</filename>
category of the Ports Collection.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="removable-drives">
<para>How do I use a new removable drive?</para>
</question>
<answer>
<para>If the drive already has a file system on it,
use a command like this:</para>
<screen>&prompt.root; <userinput>mount -t msdosfs /dev/da0s1 /mnt</userinput></screen>
<para>If the drive will only be used with &os; systems,
partition it with <acronym>UFS</acronym> or
<acronym>ZFS</acronym>. This will provide long filename
support, improvement in performance, and stability. If
the drive will be used by other operating systems, a more
portable choice, such as msdosfs, is better.</para>
<screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/da0 count=2</userinput>
&prompt.root; <userinput>gpart create -s GPT /dev/da0</userinput>
&prompt.root; <userinput>gpart add -t freebsd-ufs /dev/da0</userinput></screen>
<para>Finally, create a new file system:</para>
<screen>&prompt.root; <userinput>newfs /dev/da0p1</userinput></screen>
<para>and mount it:</para>
<screen>&prompt.root; <userinput>mount /dev/da0s1 /mnt</userinput></screen>
<para>It is a good idea to add a line to
<filename>/etc/fstab</filename> (see &man.fstab.5;) so you
can just type <command>mount /mnt</command> in the
future:</para>
<programlisting>/dev/da0p1 /mnt ufs rw,noauto 0 0</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mount-cd-superblock">
<para>Why do I get <errorname>Incorrect super
block</errorname> when mounting a CD?</para>
</question>
<answer>
<para>The type of device to mount must be specified. This
is described in the Handbook section on <link
xlink:href="&url.books.handbook;/creating-cds.html#mounting-cd">Using
Data CDs</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="cdrom-not-configured">
<para>Why do I get <errorname>Device not
configured</errorname> when mounting a CD?</para>
</question>
<answer>
<para>This generally means that there is no CD in the
drive, or the drive is not visible on the bus.
Refer to the <link
xlink:href="&url.books.handbook;/creating-cds.html#mounting-cd">Using
Data CDs</link> section of the Handbook for a detailed
discussion of this issue.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="cdrom-unicode-filenames">
<para>Why do all non-English characters in filenames show up
as <quote>?</quote> on my CDs when mounted in &os;?</para>
</question>
<answer>
<para>The CD probably uses the <quote>Joliet</quote>
extension for storing information about files and
directories. This is discussed in the Handbook section on
<link
xlink:href="&url.books.handbook;/creating-cds.html#mounting-cd">Using
Data CD-ROMs</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="burncd-isofs">
<para>A CD burned under &os; cannot be read
under any other operating system. Why?</para>
</question>
<answer>
<para>This means a raw file was burned to the CD, rather
than creating an ISO&nbsp;9660 file system. Take a look
at the Handbook section on <link
xlink:href="&url.books.handbook;/creating-cds.html#mounting-cd">Using
Data <acronym>CD</acronym>s</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="copy-cd">
<para>How can I create an image of a data CD?</para>
</question>
<answer>
<para>This is discussed in the Handbook section on <link
xlink:href="&url.books.handbook;/creating-cds.html#mkisofs">Writing
Data to an <acronym>ISO</acronym> File System</link>.
For more on working with CD-ROMs, see the <link
xlink:href="&url.books.handbook;/creating-cds.html">Creating
CDs Section</link> in the Storage chapter in the
Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mount-audio-CD">
<para>Why can I not <command>mount</command> an audio
CD?</para>
</question>
<answer>
<para>Trying to mount an audio CD will produce an error
like <errorname>cd9660: /dev/cd0: Invalid
argument</errorname>. This is because
<command>mount</command> only works on file systems.
Audio CDs do not have file systems; they just have data.
Instead, use a program that reads audio CDs, such as the
<package>audio/xmcd</package> package or port.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="multi-session-CD">
<para>How do I <command>mount</command> a multi-session
CD?</para>
</question>
<answer>
<para>By default, &man.mount.8; will attempt to mount the
last data track (session) of a CD. To
load an earlier session, use the
<option>-s</option> command line argument. Refer to
&man.mount.cd9660.8; for specific examples.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="user-floppymount">
<para>How do I let ordinary users mount CD-ROMs, DVDs,
USB drives, and other removable media?</para>
</question>
<answer>
<para>As <systemitem class="username">root</systemitem> set
the sysctl variable <varname>vfs.usermount</varname> to
<literal>1</literal>.</para>
<screen>&prompt.root; <userinput>sysctl vfs.usermount=1</userinput></screen>
<para>To make this persist across reboots, add the line
<literal>vfs.usermount=1</literal> to
<filename>/etc/sysctl.conf</filename> so that it is reset
at system boot time.</para>
<para>Users can only mount devices they have read
permissions to. To allow users to mount a device
permissions must be set in
<filename>/etc/devfs.conf</filename>.</para>
<para>For example, to allow users to mount the first USB
drive add:</para>
<programlisting># Allow all users to mount a USB drive.
own /dev/da0 root:operator
perm /dev/da0 0666</programlisting>
<para>All users can now mount devices they could read onto a
directory that they own:</para>
<screen>&prompt.user; <userinput>mkdir ~/my-mount-point</userinput>
&prompt.user; <userinput>mount -t msdosfs /dev/da0 ~/my-mount-point</userinput></screen>
<para>Unmounting the device is simple:</para>
<screen>&prompt.user; <userinput>umount ~/my-mount-point</userinput></screen>
<para>Enabling <varname>vfs.usermount</varname>, however,
has negative security implications. A better way to
access &ms-dos; formatted media is to use the
<package>emulators/mtools</package> package in the Ports
Collection.</para>
<note>
<para>The device name used in the previous examples must
be changed according to the configuration.</para>
</note>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="du-vs-df">
<para>The <command>du</command> and <command>df</command>
commands show different amounts of disk space available.
What is going on?</para>
</question>
<answer>
<para>This is due to how these commands actually work.
<command>du</command> goes through the directory tree,
measures how large each file is, and presents the totals.
<command>df</command> just asks the file system how much
space it has left. They seem to be the same thing, but a
file without a directory entry will affect
<command>df</command> but not
<command>du</command>.</para>
<para>When a program is using a file, and the file is
deleted, the file is not really removed from the file
system until the program stops using it. The file is
immediately deleted from the directory listing, however.
As an example, consider a file large enough
to affect the output of
<command>du</command> and <command>df</command>. A
file being viewed with <command>more</command> can be
deleted wihout causing an error.
The entry is
removed from the directory so no other program or user can
access it. However, <command>du</command> shows that it
is gone as it has walked the directory tree and the
file is not listed. <command>df</command> shows that it
is still there, as the file system knows that
<command>more</command> is still using that space. Once
the <command>more</command> session ends,
<command>du</command> and <command>df</command> will
agree.</para>
<para>This situation is common on web servers. Many people
set up a &os; web server and forget to rotate the log
files. The access log fills up <filename>/var</filename>.
The new administrator deletes the file, but the system
still complains that the partition is full. Stopping and
restarting the web server program would free the file,
allowing the system to release the disk space. To prevent
this from happening, set up &man.newsyslog.8;.</para>
<para>Note that Soft Updates can delay the freeing of disk
space and it can take up to 30 seconds for the
change to be visible.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="add-swap-space">
<para>How can I add more swap space?</para>
</question>
<answer>
<para>This section <link
xlink:href="&url.books.handbook;/adding-swap-space.html">of the Handbook</link>
describes how to do this.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="manufacturer-disk-size">
<para>Why does &os; see my disk as smaller than the
manufacturer says it is?</para>
</question>
<answer>
<para>Disk manufacturers calculate gigabytes as a billion
bytes each, whereas &os; calculates them as
1,073,741,824&nbsp;bytes each. This explains why, for
example, &os;'s boot messages will report a disk that
supposedly has 80&nbsp;GB as holding
76,319&nbsp;MB.</para>
<para>Also note that &os; will (by default) <link
linkend="disk-more-than-full">reserve</link> 8% of the
disk space.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="disk-more-than-full">
<para>How is it possible for a partition to be more than
100% full?</para>
</question>
<answer>
<para>A portion of each UFS partition (8%, by default) is
reserved for use by the operating system and the
<systemitem class="username">root</systemitem> user.
&man.df.1; does not count that space when calculating the
<literal>Capacity</literal> column, so it can exceed 100%.
Notice that the <literal>Blocks</literal>
column is always greater than the sum of the
<literal>Used</literal> and <literal>Avail</literal>
columns, usually by a factor of 8%.</para>
<para>For more details, look up <option>-m</option> in
&man.tunefs.8;.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="all-about-zfs">
<title>ZFS</title>
<qandaset>
<qandaentry>
<question xml:id="how-much-ram-for-zfs">
<para>What is the minimum amount of RAM one should have to
run ZFS?</para>
</question>
<answer>
<para>A minimum of 4GB of RAM is required for comfortable
usage, but individual workloads can vary widely.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="what-is-zil">
<para>What is the ZIL and when does it get used?</para>
</question>
<answer>
<para>The <acronym>ZIL</acronym> (<acronym>ZFS</acronym>
intent log) is a write log used to implement posix write
commitment semantics across crashes. Normally writes
are bundled up into transaction groups and written to
disk when filled (<quote>Transaction Group
Commit</quote>). However syscalls like &man.fsync.2;
require a commitment that the data is written to stable
storage before returning. The ZIL is needed for writes
that have been acknowledged as written but which are not
yet on disk as part of a transaction. The transaction
groups are timestamped. In the event of a crash the
last valid timestamp is found and missing data is merged
in from the ZIL.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="need-ssd-for-zil">
<para>Do I need a SSD for ZIL?</para>
</question>
<answer>
<para>By default, ZFS stores the ZIL in the pool with all
the data. If an application has a heavy write load,
storing the ZIL in a separate device that has very fast
synchronous, sequential write performance can improve
overall system. For other workloads, a SSD is unlikely
to make much of an improvement.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="what-is-l2arc">
<para>What is the L2ARC?</para>
</question>
<answer>
<para>The <acronym>L2ARC</acronym> is a read cache stored
on a fast device such as an <acronym>SSD</acronym>.
This cache is not persistent across reboots. Note that
RAM is used as the first layer of cache and the L2ARC is
only needed if there is insufficient RAM.</para>
<para>L2ARC needs space in the ARC to index it. So,
perversely, a working set that fits perfectly in the
ARC will not fit perfectly any more if a L2ARC is used
because part of the ARC is holding the L2ARC index,
pushing part of the working set into the L2ARC which is
slower than RAM.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="should-enable-dedup">
<para>Is enabling deduplication advisable?</para>
</question>
<answer>
<para>Generally speaking, no.</para>
<para>Deduplication takes up a significant amount of RAM
and may slow down read and write disk access times.
Unless one is storing data that is very heavily
duplicated, such as virtual machine images or user
backups, it is possible that deduplication will do more
harm than good. Another consideration is the inability
to revert deduplication status. If data is written when
deduplication is enabled, disabling dedup will not cause
those blocks which were deduplicated to be replicated
until they are next modified.</para>
<para>Deduplication can also lead to some unexpected
situations. In particular, deleting files may become
much slower.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="zpool-fully-full">
<para>I cannot delete or create files on my ZFS pool.
How can I fix this?</para>
</question>
<answer>
<para>This could happen because the pool is 100% full.
ZFS requires space on the disk to write transaction
metadata. To restore the pool to a usable state,
truncate the file to delete:</para>
<screen>&prompt.user; <userinput>truncate -s 0 unimportant-file</userinput></screen>
<para>File truncation works because a new transaction is
not started, new spare blocks are created
instead.</para>
<note>
<para>On systems with additional ZFS dataset tuning,
such as deduplication, the space may not be
immediately available</para>
</note>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="zfs-ssd-trim">
<para>Does ZFS support TRIM for Solid State Drives?</para>
</question>
<answer>
<para>ZFS TRIM support was added to &os;&nbsp;10-CURRENT
with revision r<revnumber>240868</revnumber>. ZFS TRIM
support was added to all &os;-STABLE branches in
r<revnumber>252162</revnumber> and
r<revnumber>251419</revnumber>, respectively.</para>
<para>ZFS TRIM is enabled by default, and can be turned
off by adding this line to
<filename>/etc/sysctl.conf</filename>:</para>
<programlisting>vfs.zfs.trim_disable=1</programlisting>
<note>
<para>ZFS TRIM may not work with all configurations,
such as a ZFS filesystem on a GELI-backed
device.</para>
</note>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="admin">
<title>System Administration</title>
<qandaset>
<qandaentry>
<question xml:id="startup-config-files">
<para>Where are the system start-up configuration
files?</para>
</question>
<answer>
<para>The primary configuration file is
<filename>/etc/defaults/rc.conf</filename> which is
described in &man.rc.conf.5;. System startup scripts
such as <filename>/etc/rc</filename> and
<filename>/etc/rc.d</filename>, which are described in
&man.rc.8;, include this file. <emphasis>Do not edit this
file!</emphasis> Instead, to edit an entry in
<filename>/etc/defaults/rc.conf</filename>, copy the line
into <filename>/etc/rc.conf</filename> and change it
there.</para>
<para>For example, if to start &man.named.8;, the
included DNS server:</para>
<screen>&prompt.root; <userinput>echo 'named_enable="YES"' &gt;&gt; /etc/rc.conf</userinput></screen>
<para>To start up local services, place shell scripts in the
<filename>/usr/local/etc/rc.d</filename> directory. These
shell scripts should be set executable, the default file
mode is <literal>555</literal>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="adding-users">
<para>How do I add a user easily?</para>
</question>
<answer>
<para>Use the &man.adduser.8; command, or the &man.pw.8;
command for more complicated situations.</para>
<para>To remove the user, use the &man.rmuser.8; command or,
if necessary, &man.pw.8;.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="root-not-found-cron-errors">
<para>Why do I keep getting messages like <errorname>root:
not found</errorname> after editing
<filename>/etc/crontab</filename>?</para>
</question>
<answer>
<para>This is normally caused by editing the system crontab.
This is not the correct way to do things as the system
crontab has a different format to the per-user crontabs.
The system
crontab has an extra field, specifying which user to run
the command as. &man.cron.8; assumes this user is the
first word of the command to execute. Since no such
command exists, this error message is displayed.</para>
<para>To delete the extra, incorrect crontab:</para>
<screen>&prompt.root; <userinput>crontab -r</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="su-wheel-group">
<para>Why do I get the error, <errorname>you are not in the
correct group to su root</errorname> when I try to
<command>su</command> to <systemitem
class="username">root</systemitem>?</para>
</question>
<answer>
<para>This is a security feature. In order to
<command>su</command> to
<systemitem class="username">root</systemitem>, or any
other account with superuser privileges, the user account
must be a member of the
<systemitem class="groupname">wheel</systemitem> group.
If this feature were not there, anybody with an
account on a system who also found out <systemitem
class="username">root</systemitem>'s password would be
able to gain superuser level access to the system.</para>
<para>To allow someone to <command>su</command> to
<systemitem class="username">root</systemitem>, put
them in the <systemitem
class="groupname">wheel</systemitem> group using
<command>pw</command>:</para>
<screen>&prompt.root; <userinput>pw groupmod wheel -m lisa</userinput></screen>
<para>The above example will add user <systemitem
class="username">lisa</systemitem> to the group
<systemitem class="groupname">wheel</systemitem>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="rcconf-readonly">
<para>I made a mistake in <filename>rc.conf</filename>, or
another startup file, and now I cannot edit it because the
file system is read-only. What should I do?</para>
</question>
<answer>
<para>Restart the system using <userinput>boot
-s</userinput> at the loader prompt to enter single-user
mode. When prompted for a shell pathname, press
<keycap>Enter</keycap> and run <command>mount
-urw /</command> to re-mount the root file system in
read/write mode. You may also need to run <command>mount
-a -t ufs</command> to mount the file system where your
favorite editor is defined. If that editor is on
a network file system, either configure
the network manually before mounting the network file
systems, or use an editor which resides on a local file
system, such as &man.ed.1;.</para>
<para>In order to use a full screen editor such as
&man.vi.1; or &man.emacs.1;, run
<command>export TERM=xterm</command>
so that these editors can load the correct data from the
&man.termcap.5; database.</para>
<para>After performing these steps, edit
<filename>/etc/rc.conf</filename> to
fix the syntax error. The error message displayed
immediately after the kernel boot messages should indicate
the number of the line in the file which is at
fault.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="printer-setup">
<para>Why am I having trouble setting up my printer?</para>
</question>
<answer>
<para>See the <link
xlink:href="&url.books.handbook;/printing.html">Handbook
entry on printing</link> for troubleshooting
tips.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="keyboard-mappings">
<para>How can I correct the keyboard mappings for my
system?</para>
</question>
<answer>
<para>Refer to the Handbook section on <link
xlink:href="&url.books.handbook;/using-localization.html">using
localization</link>, specifically the section on <link
xlink:href="&url.books.handbook;/using-localization.html#setting-console">console
setup</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="user-quotas">
<para>Why can I not get user quotas to work properly?</para>
</question>
<answer>
<orderedlist>
<listitem>
<para>It is possible that the kernel is not configured
to use quotas. In this case,
add the following line to the kernel configuration
file and recompile the kernel:</para>
<programlisting>options QUOTA</programlisting>
<para>Refer to the <link
xlink:href="&url.books.handbook;/quotas.html">Handbook
entry on quotas</link> for full details.</para>
</listitem>
<listitem>
<para>Do not turn on quotas on
<filename>/</filename>.</para>
</listitem>
<listitem>
<para>Put the quota file on the file system that the
quotas are to be enforced on:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>File System</entry>
<entry>Quota file</entry>
</row>
</thead>
<tbody>
<row>
<entry><filename>/usr</filename></entry>
<entry><filename>/usr/admin/quotas</filename></entry>
</row>
<row>
<entry><filename>/home</filename></entry>
<entry><filename>/home/admin/quotas</filename></entry>
</row>
<row>
<entry>&hellip;</entry>
<entry>&hellip;</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</listitem>
</orderedlist>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="sysv-ipc">
<para>Does &os; support System V IPC primitives?</para>
</question>
<answer>
<para>Yes, &os; supports System V-style IPC, including
shared memory, messages and semaphores, in the
<filename>GENERIC</filename> kernel. With a custom
kernel, support may be loaded with the
<filename>sysvshm.ko</filename>,
<filename>sysvsem.ko</filename> and
<filename>sysvmsg.ko</filename> kernel modules, or
enabled in the custom kernel by adding the following lines
to the kernel configuration file:</para>
<programlisting>options SYSVSHM # enable shared memory
options SYSVSEM # enable for semaphores
options SYSVMSG # enable for messaging</programlisting>
<para>Recompile and install the kernel.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="sendmail-alternative">
<para>What other mail-server software can I use instead of
<application>Sendmail</application>?</para>
</question>
<answer>
<para>The <link
xlink:href="http://www.sendmail.org/"><application>Sendmail</application></link>
server is the default mail-server software for &os;, but
it can be replaced with another
MTA installed from the Ports Collection. Available ports
include <package>mail/exim</package>,
<package>mail/postfix</package>, and
<package>mail/qmail</package>. Search the mailing lists
for discussions regarding the advantages and disadvantages
of the available MTAs.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="forgot-root-pw">
<para>I have forgotten the <systemitem
class="username">root</systemitem> password! What do I
do?</para>
</question>
<answer>
<para>Do not panic! Restart the system, type
<userinput>boot -s</userinput> at the
<literal>Boot:</literal> prompt to enter single-user mode.
At the question about the shell to use, hit
<keycap>Enter</keycap> which will display a
&prompt.root; prompt. Enter <command>mount
-urw /</command> to remount the root file system
read/write, then run <command>mount -a</command> to
remount all the file systems. Run <command>passwd
root</command> to change the <systemitem
class="username">root</systemitem> password then run
&man.exit.1; to continue booting.</para>
<note>
<para>If you are still prompted to give the <systemitem
class="username">root</systemitem> password when
entering the single-user mode, it means that the console
has been marked as <literal>insecure</literal> in
<filename>/etc/ttys</filename>. In this case, it will
be required to boot from a &os; installation disk,
choose the <guimenuitem>Live CD</guimenuitem> or
<guimenuitem>Shell</guimenuitem> at the beginning of the
install process and issue the commands mentioned above.
Mount the specific partition in this
case and then chroot to it. For example, replace
<command>mount -urw /</command> with
<command>mount /dev/ada0p1 /mnt; chroot /mnt</command>
for a system on
<replaceable>ada0p1</replaceable>.</para>
</note>
<note>
<para>If the root partition cannot be mounted from
single-user mode, it is possible that the partitions are
encrypted and it is impossible to mount them without the
access keys. For more information see the section
about encrypted disks in the &os; <link
xlink:href="&url.books.handbook;/disks-encrypting.html">Handbook</link>.</para>
</note>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="CAD-reboot">
<para>How do I keep <keycombo
action="simul"><keycap>Control</keycap><keycap>Alt</keycap><keycap>Delete</keycap></keycombo>
from rebooting the system?</para>
</question>
<answer>
<para>When using &man.syscons.4;, the default console
driver, build and install a new kernel with this line in
the configuration file:</para>
<programlisting>options SC_DISABLE_REBOOT</programlisting>
<para>This can also be done by setting the following
&man.sysctl.8; which does not require a reboot or kernel
recompile:</para>
<screen>&prompt.root; <userinput>sysctl hw.syscons.kbd_reboot=0</userinput></screen>
<note>
<para>The above two methods are exclusive: The
&man.sysctl.8; does not exist if the kernel is compiled
with <literal>SC_DISABLE_REBOOT</literal>.</para>
</note>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="dos-to-unix-txt">
<para>How do I reformat DOS text files to &unix;
ones?</para>
</question>
<answer>
<para>Use this &man.perl.1; command:</para>
<screen>&prompt.user; <userinput>perl -i.bak -npe 's/\r\n/\n/g' file(s)</userinput></screen>
<para>where <replaceable>file(s)</replaceable> is one or
more files to process. The modification is done in-place,
with the original file stored with a
<filename>.bak</filename> extension.</para>
<para>Alternatively, use &man.tr.1;:</para>
<screen>&prompt.user; <userinput>tr -d '\r' &lt; dos-text-file &gt; unix-file</userinput></screen>
<para><replaceable>dos-text-file</replaceable> is the file
containing DOS text while
<replaceable>unix-file</replaceable> will contain the
converted output. This can be quite a bit faster than
using <command>perl</command>.</para>
<para>Yet another way to reformat DOS text files is to use
the <package>converters/dosunix</package> port from the
Ports Collection. Consult its documentation about the
details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="reread-rc">
<para>How do I re-read <filename>/etc/rc.conf</filename> and
re-start <filename>/etc/rc</filename> without a
reboot?</para>
</question>
<answer>
<para>Go into single-user mode and then back to multi-user
mode:</para>
<screen>&prompt.root; <userinput>shutdown now</userinput>
&prompt.root; <userinput>return</userinput>
&prompt.root; <userinput>exit</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="release-candidate">
<para>I tried to update my system to the latest
<emphasis>-STABLE</emphasis>, but got
<emphasis>-BETA<replaceable>x</replaceable></emphasis>,
<emphasis>-RC</emphasis> or
<emphasis>-PRERELEASE</emphasis>! What is going
on?</para>
</question>
<answer>
<para>Short answer: it is just a name.
<emphasis>RC</emphasis> stands for <quote>Release
Candidate</quote>. It signifies that a release is
imminent. In &os;, <emphasis>-PRERELEASE</emphasis> is
typically synonymous with the code freeze before a
release. (For some releases, the
<emphasis>-BETA</emphasis> label was used in the same way
as <emphasis>-PRERELEASE</emphasis>.)</para>
<para>Long answer: &os; derives its releases from one of two
places. Major, dot-zero, releases, such as 9.0-RELEASE
are branched from the head of the development stream,
commonly referred to as <link
linkend="current">-CURRENT</link>. Minor releases, such
as 6.3-RELEASE or 5.2-RELEASE, have been snapshots of the
active <link linkend="stable">-STABLE</link> branch.
Starting with 4.3-RELEASE, each release also now has its
own branch which can be tracked by people requiring an
extremely conservative rate of development (typically only
security advisories).</para>
<para>When a release is about to be made, the branch from
which it will be derived from has to undergo a certain
process. Part of this process is a code freeze. When a
code freeze is initiated, the name of the branch is
changed to reflect that it is about to become a release.
For example, if the branch used to be called 6.2-STABLE,
its name will be changed to 6.3-PRERELEASE to signify the
code freeze and signify that extra pre-release testing
should be happening. Bug fixes can still be committed to
be part of the release. When the source code is in shape
for the release the name will be changed to 6.3-RC to
signify that a release is about to be made from it. Once
in the RC stage, only the most critical bugs found can be
fixed. Once the release (6.3-RELEASE in this example) and
release branch have been made, the branch will be renamed
to 6.3-STABLE.</para>
<para>For more information on version numbers and the
various Subversion branches, refer to the <link
xlink:href="&url.articles.releng;/article.html">Release
Engineering</link> article.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="kernel-chflag-failure">
<para>I tried to install a new kernel, and the
&man.chflags.1; failed. How do I get around this?</para>
</question>
<answer>
<para>Short answer: the security level is
greater than 0. Reboot directly to single-user mode to
install the kernel.</para>
<para>Long answer: &os; disallows changing system flags at
security levels greater than 0. To check the current
security level:</para>
<screen>&prompt.root; <userinput>sysctl kern.securelevel</userinput></screen>
<para>The security level cannot be lowered in multi-user
mode, so boot to single-user mode to install the kernel,
or change the security level in
<filename>/etc/rc.conf</filename> then reboot. See the
&man.init.8; manual page for details on
<literal>securelevel</literal>, and see
<filename>/etc/defaults/rc.conf</filename> and the
&man.rc.conf.5; manual page for more information on
<filename>rc.conf</filename>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="kernel-securelevel-time">
<para>I cannot change the time on my system by more than one
second! How do I get around this?</para>
</question>
<answer>
<para>Short answer: the system is at a security level
greater than 1. Reboot directly to single-user mode to
change the date.</para>
<para>Long answer: &os; disallows changing the time by more
that one second at security levels greater than 1. To
check the security level:</para>
<screen>&prompt.root; <userinput>sysctl kern.securelevel</userinput></screen>
<para>The security level cannot be lowered in multi-user
mode. Either boot to single-user mode to change the date
or change the security level in
<filename>/etc/rc.conf</filename> and reboot. See the
&man.init.8; manual page for details on
<literal>securelevel</literal>, and see
<filename>/etc/defaults/rc.conf</filename> and the
&man.rc.conf.5; manual page for more information on
<filename>rc.conf</filename>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="statd-mem-leak">
<para>Why is <command>rpc.statd</command> using 256&nbsp;MB
of memory?</para>
</question>
<answer>
<para>No, there is no memory leak, and it is not using
256&nbsp;MB of memory. For convenience,
<command>rpc.statd</command> maps an obscene amount of
memory into its address space. There is nothing terribly
wrong with this from a technical standpoint; it just
throws off things like &man.top.1; and &man.ps.1;.</para>
<para>&man.rpc.statd.8; maps its status file (resident on
<filename>/var</filename>) into its address space; to save
worrying about remapping it later when it needs to grow,
it maps it with a generous size. This is very evident
from the source code, where one can see that the length
argument to &man.mmap.2; is <literal>0x10000000</literal>,
or one sixteenth of the address space on an IA32, or
exactly 256&nbsp;MB.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="unsetting-schg">
<para>Why can I not unset the <literal>schg</literal> file
flag?</para>
</question>
<answer>
<para>The system is running a securelevel greater than 0.
Lower the securelevel and try again. For
more information, see <link linkend="securelevel">the <acronym>FAQ</acronym>
entry on securelevel</link> and the &man.init.8; manual
page.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="vnlru">
<para>What is <literal>vnlru</literal>?</para>
</question>
<answer>
<para><literal>vnlru</literal> flushes and frees vnodes when
the system hits the <varname>kern.maxvnodes</varname>
limit. This kernel thread sits mostly idle, and only
activates when there is a huge amount of RAM and users are
accessing tens of thousands of tiny files.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="top-memory-states">
<para>What do the various memory states displayed by
<command>top</command> mean?</para>
</question>
<!-- Provided by John Dyson via Usenet -->
<answer>
<itemizedlist>
<listitem>
<para><literal>Active</literal>: pages recently
statistically used.</para>
</listitem>
<listitem>
<para><literal>Inactive</literal>: pages recently
statistically unused.</para>
</listitem>
<listitem>
<para><literal>Cache</literal>: (most often) pages that
have percolated from inactive to a status where they
maintain their data, but can often be immediately
reused (either with their old association, or reused
with a new association). There can be certain
immediate transitions from <literal>active</literal>
to <literal>cache</literal> state if the page is known
to be clean (unmodified), but that transition is a
matter of policy, depending upon the algorithm choice
of the VM system maintainer.</para>
</listitem>
<listitem>
<para><literal>Free</literal>: pages without data
content, and can be immediately used in certain
circumstances where cache pages might be ineligible.
Free pages can be reused at interrupt or process
state.</para>
</listitem>
<listitem>
<para><literal>Wired</literal>: pages that are fixed
into memory, usually for kernel purposes, but also
sometimes for special use in processes.</para>
</listitem>
</itemizedlist>
<para>Pages are most often written to disk (sort of a VM
sync) when they are in the inactive state, but active
pages can also be synced. This depends upon the CPU
tracking of the modified bit being available, and in
certain situations there can be an advantage for a block
of VM pages to be synced, whether they are active or
inactive. In most common cases, it is best to think of
the inactive queue to be a queue of relatively unused
pages that might or might not be in the process of being
written to disk. Cached pages are already synced, not
mapped, but available for immediate process use with their
old association or with a new association. Free pages are
available at interrupt level, but cached or free pages can
be used at process state for reuse. Cache pages are not
adequately locked to be available at interrupt
level.</para>
<para>There are some other flags (e.g., busy flag or busy
count) that might modify some of the described
rules.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="free-memory-amount">
<para>How much free memory is available?</para>
</question>
<!-- Provided by John Dyson via Usenet -->
<answer>
<para>There are a couple of kinds of <quote>free
memory</quote>. One kind is the amount of memory
immediately available without paging anything else out.
That is approximately the size of cache queue + size of
free queue (with a derating factor, depending upon system
tuning). Another kind of <quote>free memory</quote> is
the total amount of <acronym>VM</acronym> space. That can
be complex, but is dependent upon the amount of swap space
and memory. Other kinds of <quote>free memory</quote>
descriptions are also possible, but it is relatively
useless to define these, but rather it is important to
make sure that the paging rate is kept low, and to avoid
running out of swap space.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="var-empty">
<para>What is <filename>/var/empty</filename>?</para>
</question>
<answer>
<para><filename>/var/empty</filename> is a directory that
the &man.sshd.8; program uses when performing privilege
separation. The <filename>/var/empty</filename>
directory is empty, owned by <systemitem
class="username">root</systemitem> and has the
<literal>schg</literal> flag set. This directory should
not be deleted.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="newsyslog-expectations">
<para>I just changed
<filename>/etc/newsyslog.conf</filename>. How can I check
if it does what I expect?</para>
</question>
<answer>
<para>To see what &man.newsyslog.8; will do, use the
following:</para>
<screen>&prompt.user; <userinput>newsyslog -nrvv</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="timezone">
<para>My time is wrong, how can I change the
timezone?</para>
</question>
<answer>
<para>Use &man.tzsetup.8;.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="x">
<title>The X Window System and Virtual Consoles</title>
<qandaset>
<qandaentry>
<question xml:id="whatis-X">
<para>What is the X Window System?</para>
</question>
<answer>
<para>The X Window System (commonly <literal>X11</literal>)
is the most widely available windowing system capable of
running on &unix; or &unix;&nbsp;like systems, including
&os;. <link xlink:href="http://www.x.org/wiki/">The X.Org
Foundation</link> administers the <link
xlink:href="http://en.wikipedia.org/wiki/X_Window_System_core_protocol">X
protocol standards</link>, with the current reference
implementation, version 11 release &xorg.version;, so
references are often shortened to
<literal>X11</literal>.</para>
<para>Many implementations are available for different
architectures and operating systems. An implementation of
the server-side code is properly known as an <literal>X
server</literal>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="running-X">
<para>I want to run &xorg;, how do I go about it?</para>
</question>
<answer>
<para>To install &xorg; do one of the following:</para>
<para>Use the <package>x11/xorg</package>
meta-port, which builds and installs every &xorg;
component.</para>
<para>Use <package>x11/xorg-minimal</package>, which builds
and installs only the necessary &xorg; components.</para>
<para>Install &xorg; from &os; packages:</para>
<screen><userinput>&prompt.root; pkg install xorg</userinput></screen>
<para>After the installation of &xorg;, follow the
instructions from the <link
xlink:href="&url.books.handbook;/x-config.html">X11
Configuration</link> section of the &os;
Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="running-X-securelevels">
<para>I <emphasis>tried</emphasis> to run X, but I get a
<errorname>No devices detected.</errorname> error when I
type <command>startx</command>. What do I do now?</para>
</question>
<answer>
<para>The system is probably running at a raised
<literal>securelevel</literal>. It is not possible to
start X at a raised <literal>securelevel</literal> because
X requires write access to &man.io.4;. For more
information, see at the &man.init.8; manual page.</para>
<para>There are two solutions to the problem: set the
<literal>securelevel</literal> back down to zero or run
&man.xdm.1; (or an alternative display manager) at boot
time before the <literal>securelevel</literal> is
raised.</para>
<para>See <xref linkend="xdm-boot"/> for more information
about running &man.xdm.1; at boot time.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="x-and-moused">
<para>Why does my mouse not work with X?</para>
</question>
<answer>
<para>When using &man.syscons.4;, the default console
driver, &os; can be configured to support a mouse pointer
on each virtual screen. To avoid conflicting with X,
&man.syscons.4; supports a virtual device called
<filename>/dev/sysmouse</filename>. All mouse events
received from the real mouse device are written to the
&man.sysmouse.4; device via &man.moused.8;. To use the
mouse on one or more virtual consoles,
<emphasis>and</emphasis> use X, see <xref
linkend="moused" remap="another section"/> and set up
&man.moused.8;.</para>
<para>Then edit <filename>/etc/X11/xorg.conf</filename> and
make sure the following lines exist:</para>
<programlisting>Section "InputDevice"
Option "Protocol" "SysMouse"
Option "Device" "/dev/sysmouse"
.....</programlisting>
<para>Starting with &xorg; version 7.4, the
<literal>InputDevice</literal> sections in
<filename>xorg.conf</filename> are ignored in favor of
autodetected devices. To restore the old behavior, add
the following line to the <literal>ServerLayout</literal>
or <literal>ServerFlags</literal> section:</para>
<programlisting>Option "AutoAddDevices" "false"</programlisting>
<para>Some people prefer to use
<filename>/dev/mouse</filename> under X. To make this
work, <filename>/dev/mouse</filename> should be linked
to <filename>/dev/sysmouse</filename> (see
&man.sysmouse.4;) by adding the following line to
<filename>/etc/devfs.conf</filename> (see
&man.devfs.conf.5;):</para>
<programlisting>link sysmouse mouse</programlisting>
<para>This link can be created by restarting &man.devfs.5;
with the following command (as <systemitem
class="username">root</systemitem>):</para>
<screen>&prompt.root; <userinput>service devfs restart</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="x-and-wheel">
<para>My mouse has a fancy wheel. Can I use it in X?</para>
</question>
<answer>
<para>Yes, if X is configured for a 5 button mouse. To
do this, add the lines <literal>Buttons 5</literal>
and <literal>ZAxisMapping 4 5</literal> to the
<quote>InputDevice</quote> section of
<filename>/etc/X11/xorg.conf</filename>, as seen in this
example:</para>
<programlisting>Section "InputDevice"
Identifier "Mouse1"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/sysmouse"
Option "Buttons" "5"
Option "ZAxisMapping" "4 5"
EndSection</programlisting>
<para>To use the mouse in
<application>Emacs</application>, also add the following
lines to<filename>~/.emacs</filename>:</para>
<programlisting>;; wheel mouse
(global-set-key [mouse-4] 'scroll-down)
(global-set-key [mouse-5] 'scroll-up)</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="x-and-synaptic">
<para>My laptop has a Synaptics touchpad. Can I use it in
X?</para>
</question>
<answer>
<para>Yes, after configuring a few things to make
it work.</para>
<para>In order to use the Xorg synaptics driver,
first remove <literal>moused_enable</literal> from
<filename>rc.conf</filename>.</para>
<para>To enable synaptics, add the following line to
<filename>/boot/loader.conf</filename>:</para>
<programlisting>hw.psm.synaptics_support="1"</programlisting>
<para>Add the following to
<filename>/etc/X11/xorg.conf</filename>:</para>
<programlisting>Section "InputDevice"
Identifier "Touchpad0"
Driver "synaptics"
Option "Protocol" "psm"
Option "Device" "/dev/psm0"
EndSection</programlisting>
<para>And be sure to add the following into the
<quote>ServerLayout</quote> section:</para>
<programlisting>InputDevice "Touchpad0" "SendCoreEvents"</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="no-remote-x11">
<para>How do I use remote X displays?</para>
</question>
<answer>
<para>For security reasons, the default setting is to not
allow a machine to remotely open a window.</para>
<para>To enable this feature, start
<application>X</application> with the optional
<option>-listen_tcp</option> argument:</para>
<screen>&prompt.user; <userinput>startx -listen_tcp</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="virtual-console">
<para>What is a virtual console and how do I make
more?</para>
</question>
<answer>
<para>Virtual consoles provide
several simultaneous sessions on the same machine without
doing anything complicated like setting up a network or
running X.</para>
<para>When the system starts, it will display a login prompt
on the monitor after displaying all the boot messages.
Type in your login name and password to
start working on the first virtual
console.</para>
<para>To start another
session, perhaps to look at documentation for a program
or to read mail while waiting for an
FTP transfer to finish,
hold down <keycap>Alt</keycap> and press
<keycap>F2</keycap>. This will display the login prompt
for the second virtual
console. To go back to the
original session, press <keycombo
action="simul"><keycap>Alt</keycap><keycap>F1</keycap></keycombo>.</para>
<para>The default &os; installation has eight virtual
consoles enabled. <keycombo
action="simul"><keycap>Alt</keycap><keycap>F1</keycap></keycombo>,
<keycombo
action="simul"><keycap>Alt</keycap><keycap>F2</keycap></keycombo>,
<keycombo
action="simul"><keycap>Alt</keycap><keycap>F3</keycap></keycombo>,
and so on will switch between these virtual
consoles.</para>
<para>To enable more of virtual consoles, edit
<filename>/etc/ttys</filename> (see &man.ttys.5;) and add
entries for <filename>ttyv8</filename> to
<filename>ttyvc</filename>, after the comment on
<quote>Virtual terminals</quote>:</para>
<programlisting># Edit the existing entry for ttyv8 in /etc/ttys and change
# "off" to "on".
ttyv8 "/usr/libexec/getty Pc" xterm on secure
ttyv9 "/usr/libexec/getty Pc" xterm on secure
ttyva "/usr/libexec/getty Pc" xterm on secure
ttyvb "/usr/libexec/getty Pc" xterm on secure</programlisting>
<para>The more virtual
terminals, the more resources that are used. This can be
problematic on systems with 8&nbsp;MB RAM or less.
Consider changing <literal>secure</literal> to
<literal>insecure</literal>.</para>
<important>
<para>In order to run an X server, at least one virtual
terminal must be left to <literal>off</literal> for it
to use. This means that only eleven of the Alt-function
keys can be used as virtual consoles so that one is left
for the X server.</para>
</important>
<para>For example, to run X and eleven virtual consoles, the
setting for virtual terminal 12 should be:</para>
<programlisting>ttyvb "/usr/libexec/getty Pc" xterm off secure</programlisting>
<para>The easiest way to activate the
virtual consoles is to reboot.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="vty-from-x">
<para>How do I access the virtual consoles from X?</para>
</question>
<answer>
<para>Use <keycombo
action="simul"><keycap>Ctrl</keycap><keycap>Alt</keycap><keycap>F<replaceable>n</replaceable></keycap></keycombo>
to switch back to a virtual console. Press <keycombo
action="simul"><keycap>Ctrl</keycap><keycap>Alt</keycap><keycap>F1</keycap></keycombo>
to return to the first virtual console.</para>
<para>Once at a text console, use
<keycombo
action="simul"><keycap>Alt</keycap><keycap>F<replaceable>n</replaceable></keycap></keycombo>
to move between them.</para>
<para>To return to the X session, switch to the
virtual console running X. If X was started from the
command line using <command>startx</command>,
the X session will attach to the next unused virtual
console, not the text console from which it was invoked.
For eight active virtual terminals, X will
run on the ninth, so use <keycombo
action="simul"><keycap>Alt</keycap><keycap>F9</keycap></keycombo>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="xdm-boot">
<para>How do I start <application>XDM</application> on
boot?</para>
</question>
<answer>
<para>There are two schools of thought on how to start
&man.xdm.1;. One school starts <command>xdm</command>
from <filename>/etc/ttys</filename> (see &man.ttys.5;)
using the supplied example, while the other runs
<command>xdm</command> from
<filename>rc.local</filename> (see &man.rc.8;) or from an
<filename>X</filename> script in
<filename>/usr/local/etc/rc.d</filename>. Both are
equally valid, and one may work in situations where the
other does not. In both cases the result is the same: X
will pop up a graphical login prompt.</para>
<para>The &man.ttys.5; method has the advantage of
documenting which vty X will start on and passing the
responsibility of restarting the X server on logout to
&man.init.8;. The &man.rc.8; method makes it easy to
<command>kill</command> <command>xdm</command> if there is
a problem starting the X server.</para>
<para>If loaded from &man.rc.8;, <command>xdm</command>
should be started without any arguments.
<command>xdm</command> must start
<emphasis>after</emphasis> &man.getty.8; runs, or else
<command>getty</command> and <command>xdm</command> will
conflict, locking out the console. The best way around
this is to have the script sleep 10 seconds or so then
launch <command>xdm</command>.</para>
<para>When starting <command>xdm</command> from
<filename>/etc/ttys</filename>, there still is a chance of
conflict between <command>xdm</command> and &man.getty.8;.
One way to avoid this is to add the <literal>vt</literal>
number in
<filename>/usr/local/lib/X11/xdm/Xservers</filename>:</para>
<programlisting>:0 local /usr/local/bin/X vt4</programlisting>
<para>The above example will direct the X server to run in
<filename>/dev/ttyv3</filename>. Note the number is
offset by one. The X server counts the vty from one,
whereas the &os; kernel numbers the vty from zero.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="xconsole-failure">
<para>Why do I get <errorname>Couldn't open
console</errorname> when I run
<command>xconsole</command>?</para>
</question>
<answer>
<para>When <application>X</application> is started with
<command>startx</command>, the permissions on
<filename>/dev/console</filename> will
<emphasis>not</emphasis> get changed, resulting in things
like <command>xterm -C</command> and
<command>xconsole</command> not working.</para>
<para>This is because of the way console permissions are set
by default. On a multi-user system, one does not
necessarily want just any user to be able to write on the
system console. For users who are logging directly onto a
machine with a VTY, the &man.fbtab.5; file exists to solve
such problems.</para>
<para>In a nutshell, make sure an uncommented line of the
form is in <filename>/etc/fbtab</filename> (see
&man.fbtab.5;):</para>
<programlisting>/dev/ttyv0 0600 /dev/console</programlisting>
<para>It will ensure that whomever logs in on
<filename>/dev/ttyv0</filename> will own the
console.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ps2-x">
<para>Why does my PS/2 mouse misbehave under X?</para>
</question>
<answer>
<para>The mouse and the mouse driver may have become out of
synchronization. In rare cases, the driver may also
erroneously report synchronization errors:</para>
<programlisting>psmintr: out of sync (xxxx != yyyy)</programlisting>
<para>If this happens, disable the synchronization check
code by setting the driver flags for the PS/2 mouse driver
to <literal>0x100</literal>. This can be easiest achieved
by adding <literal>hint.psm.0.flags="0x100"</literal> to
<filename>/boot/loader.conf</filename> and
rebooting.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mouse-button-reverse">
<para>How do I reverse the mouse buttons?</para>
</question>
<answer>
<para>Type
<command>xmodmap -e "pointer = 3 2 1"</command>. Add this
command to <filename>~/.xinitrc</filename> or
<filename>~/.xsession</filename> to make it happen
automatically.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="install-splash">
<para>How do I install a splash screen and where do I find
them?</para>
</question>
<answer>
<para>The detailed answer for this question can be found in
the <link
xlink:href="&url.books.handbook;/boot-splash.html">Boot
Time Splash Screens</link> section of the &os;
Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="windows-keys">
<para>Can I use the <keycap>Windows</keycap> keys on my
keyboard in X?</para>
</question>
<answer>
<para>Yes. Use &man.xmodmap.1; to
define which functions the keys should perform.</para>
<para>Assuming all Windows keyboards are
standard, the keycodes for these three keys are the
following:</para>
<itemizedlist>
<listitem>
<para><keycode>115</keycode> &mdash;
<keycap>Windows</keycap> key, between the left-hand
<keycap>Ctrl</keycap> and <keycap>Alt</keycap>
keys</para>
</listitem>
<listitem>
<para><keycode>116</keycode> &mdash;
<keycap>Windows</keycap> key, to the right of
<keycap>AltGr</keycap></para>
</listitem>
<listitem>
<para><keycode>117</keycode> &mdash;
<keycap>Menu</keycap>, to the left of the right-hand
<keycap>Ctrl</keycap></para>
</listitem>
</itemizedlist>
<para>To have the left <keycap>Windows</keycap> key print a
comma, try this.</para>
<screen>&prompt.root; <userinput>xmodmap -e "keycode 115 = comma"</userinput></screen>
<para>To have the <keycap>Windows</keycap> key-mappings
enabled automatically every time X is started, either put
the <command>xmodmap</command> commands in
<filename>~/.xinitrc</filename> or, preferably, create
a <filename>~/.xmodmaprc</filename> and include the
<command>xmodmap</command> options, one per line, then add
the following line to
<filename>~/.xinitrc</filename>:</para>
<programlisting>xmodmap $HOME/.xmodmaprc</programlisting>
<para>For example, to map the 3 keys to be
<keycap>F13</keycap>, <keycap>F14</keycap>, and
<keycap>F15</keycap>, respectively. This would make it
easy to map them to useful functions within applications
or the window manager.</para>
<para>To do this, put the following in
<filename>~/.xmodmaprc</filename>.</para>
<programlisting>keycode 115 = F13
keycode 116 = F14
keycode 117 = F15</programlisting>
<para>For the <package>x11-wm/fvwm2</package> desktop
manager, one could map the keys so that
<keycap>F13</keycap> iconifies or de-iconifies the
window the cursor is in, <keycap>F14</keycap> brings the
window the cursor is in to the front or, if it is already
at the front, pushes it to the back, and
<keycap>F15</keycap> pops up the main Workplace
menu even if the cursor is not on the
desktop, which is useful when no part of
the desktop is visible.</para>
<para>The following entries in
<filename>~/.fvwmrc</filename> implement the
aforementioned setup:</para>
<programlisting>Key F13 FTIWS A Iconify
Key F14 FTIWS A RaiseLower
Key F15 A A Menu Workplace Nop</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="x-3d-acceleration">
<para>How can I get 3D hardware acceleration for
&opengl;?</para>
</question>
<answer>
<para>The availability of 3D acceleration depends on the
version of &xorg; and the type of video
chip. For an nVidia chip, use
the binary drivers provided for &os; by installing one of
the following ports:</para>
<para>The latest versions of nVidia cards are supported
by the <package>x11/nvidia-driver</package>
port.</para>
<para>Older drivers are available as
<package>x11/nvidia-driver-<replaceable>###</replaceable></package></para>
<para>nVidia provides detailed information on which
card is supported by which driver on their web site: <uri
xlink:href="http://www.nvidia.com/object/IO_32667.html">http://www.nvidia.com/object/IO_32667.html</uri>.</para>
<para>For Matrox&nbsp;G200/G400, check the
<package>x11-drivers/xf86-video-mga</package>
port.</para>
<para>For ATI&nbsp;Rage&nbsp;128 and Radeon see
&man.ati.4x;, &man.r128.4x; and &man.radeon.4x;.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="networking">
<title>Networking</title>
<qandaset>
<qandaentry>
<question xml:id="diskless-booting">
<para>Where can I get information on <quote>diskless
booting</quote>?</para>
</question>
<answer>
<para><quote>Diskless booting</quote> means that the &os;
box is booted over a network, and reads the necessary
files from a server instead of its hard disk. For full
details, see <link
xlink:href="&url.books.handbook;/network-diskless.html">the
Handbook entry on diskless booting</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="router">
<para>Can a &os; box be used as a dedicated network
router?</para>
</question>
<answer>
<para>Yes. Refer to the Handbook entry on <link
xlink:href="&url.books.handbook;/advanced-networking.html">advanced
networking</link>, specifically the section on <link
xlink:href="&url.books.handbook;/network-routing.html">routing
and gateways</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="win95-connection">
<para>Can I connect my &windows; box to the Internet via
&os;?</para>
</question>
<answer>
<para>Typically, people who ask this question have two PCs
at home, one with &os; and one with some version of
&windows; the idea is to use the &os; box to connect to
the Internet and then be able to access the Internet from
the &windows; box through the &os; box. This is really
just a special case of the previous question and works
perfectly well.</para>
<para>Dialup users must use <option>-nat</option>
and set <literal>gateway_enable</literal> to
<emphasis>YES</emphasis> in
<filename>/etc/rc.conf</filename>. For more information,
refer to &man.ppp.8; or the <link
xlink:href="&url.books.handbook;/userppp.html">Handbook
entry on user PPP</link>.</para>
<para>If the connection to the Internet is over Ethernet,
use &man.natd.8;. A tutorial can be found in the <link
xlink:href="&url.books.handbook;/firewalls-ipfw.html#network-natd">natd</link>
section of the Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="slip-ppp-support">
<para>Does &os; support PPP?</para>
</question>
<answer>
<para>Yes. &man.ppp.8; provides support for both incoming
and outgoing connections.</para>
<para>For more information on how to use this, refer to
the <link
xlink:href="&url.books.handbook;/ppp-and-slip.html">Handbook
chapter on PPP</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="natd">
<para>Does &os; support NAT or Masquerading?</para>
</question>
<answer>
<para>Yes. For instructions on how to use NAT over a PPP
connection, see the <link
xlink:href="&url.books.handbook;/userppp.html">Handbook
entry on PPP</link>. To use NAT over
some other sort of network connection, look at the
<link
xlink:href="&url.books.handbook;/firewalls-ipfw.html#network-natd">natd</link>
section of the Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ethernet-aliases">
<para>How can I set up Ethernet aliases?</para>
</question>
<answer>
<para>If the alias is on the same subnet as an address
already configured on the interface, add
<literal>netmask 0xffffffff</literal> to this
command:</para>
<screen>&prompt.root; <userinput>ifconfig <replaceable>ed0</replaceable> alias <replaceable>192.0.2.2 </replaceable>netmask 0xffffffff</userinput></screen>
<para>Otherwise, specify the network address and
netmask as usual:</para>
<screen>&prompt.root; <userinput>ifconfig <replaceable>ed0</replaceable> alias <replaceable>172.16.141.5</replaceable> netmask 0xffffff00</userinput></screen>
<para>More information can be found in the &os; <link
xlink:href="&url.books.handbook;/configtuning-virtual-hosts.html">Handbook</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="nfs-linux">
<para>Why can I not NFS-mount from a &linux; box?</para>
</question>
<answer>
<para>Some versions of the &linux; NFS code only accept
mount requests from a privileged port; try to issue the
following command:</para>
<screen>&prompt.root; <userinput>mount -o -P linuxbox:/blah /mnt</userinput></screen>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="exports-errors">
<para>Why does <command>mountd</command> keep telling me it
<errorname>can't change attributes</errorname> and that I
have a <errorname>bad exports list</errorname> on my &os;
NFS server?</para>
</question>
<answer>
<para>The most frequent problem is not understanding the
correct format of <filename>/etc/exports</filename>.
Review &man.exports.5; and the <link
xlink:href="&url.books.handbook;/network-nfs.html">NFS</link>
entry in the Handbook, especially the section on <link
xlink:href="&url.books.handbook;/network-nfs.html#configuring-nfs">configuring
NFS</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ip-multicast">
<para>How do I enable IP multicast support?</para>
</question>
<answer>
<para>Install the <package>net/mrouted</package> package
or port and add
<literal>mrouted_enable="YES"</literal> to
<filename>/etc/rc.conf</filename> start this service at
boot time.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="fqdn-hosts">
<para>Why do I have to use the FQDN for hosts on my
site?</para>
</question>
<answer>
<para>See the answer in the &os; <link
xlink:href="&url.books.handbook;/mail-trouble.html">Handbook</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="network-permission-denied">
<para>Why do I get an error, <errorname>Permission
denied</errorname>, for all networking
operations?</para>
</question>
<answer>
<para>If the kernel is compiled with the
<literal>IPFIREWALL</literal> option, be aware
that the default policy is to deny all packets that are
not explicitly allowed.</para>
<para>If the firewall is unintentionally misconfigured,
restore network operability by
typing the following as <systemitem
class="username">root</systemitem>:</para>
<screen>&prompt.root; <userinput>ipfw add 65534 allow all from any to any</userinput></screen>
<para>Consider setting
<literal>firewall_type="open"</literal> in
<filename>/etc/rc.conf</filename>.</para>
<para>For further information on configuring this
firewall, see the <link
xlink:href="&url.books.handbook;/firewalls-ipfw.html">Handbook
chapter</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ipfw-fwd">
<para>Why is my <command>ipfw</command> <quote>fwd</quote>
rule to redirect a service to another machine not
working?</para>
</question>
<answer>
<para>Possibly because network address translation (NAT) is
needed instead of just forwarding packets. A
<quote>fwd</quote> rule only forwards packets, it does not
actually change the data inside the packet. Consider this
rule:</para>
<screen>01000 fwd <replaceable>10.0.0.1</replaceable> from any to <replaceable>foo 21</replaceable></screen>
<para>When a packet with a destination address of
<replaceable>foo</replaceable> arrives at the machine with
this rule, the packet is forwarded to
<replaceable>10.0.0.1</replaceable>, but it still has the
destination address of <replaceable>foo</replaceable>.
The destination address of the packet is
not changed to
<replaceable>10.0.0.1</replaceable>. Most machines would
probably drop a packet that they receive with a
destination address that is not their own. Therefore,
using a <quote>fwd</quote> rule does not often work the
way the user expects. This behavior is a feature and not
a bug.</para>
<para>See the <link
linkend="service-redirect"><acronym>FAQ</acronym> about
redirecting services</link>, the &man.natd.8; manual, or
one of the several port redirecting utilities in the <link
xlink:href="&url.base;/ports/index.html">Ports
Collection</link> for a correct way to do this.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="service-redirect">
<para>How can I redirect service requests from one machine
to another?</para>
</question>
<answer>
<para>FTP and other service requests can be redirected with
the <package>sysutils/socket</package> package or port.
Replace the entry for the service in
<filename>/etc/inetd.conf</filename> to call
<command>socket</command>, as seen in this example for
<application>ftpd</application>:</para>
<programlisting>ftp stream tcp nowait nobody /usr/local/bin/socket socket <replaceable>ftp.example.com</replaceable> <replaceable>ftp</replaceable></programlisting>
<para>where <replaceable>ftp.example.com</replaceable> and
<replaceable>ftp</replaceable> are the host and port to
redirect to, respectively.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="bandwidth-mgr-tool">
<para>Where can I get a bandwidth management tool?</para>
</question>
<answer>
<para>There are three bandwidth management tools available
for &os;. &man.dummynet.4; is integrated into &os; as
part of &man.ipfw.4;. <link
xlink:href="http://www.sonycsl.co.jp/person/kjc/programs.html">ALTQ</link>
has been integrated into &os; as part of &man.pf.4;.
Bandwidth Manager from <link
xlink:href="http://www.etinc.com/">Emerging
Technologies</link> is a commercial product.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="bpf-not-configured">
<para>Why do I get <errorname>/dev/bpf0: device not
configured</errorname>?</para>
</question>
<answer>
<para>The running application requires the Berkeley
Packet Filter (&man.bpf.4;), but it was removed from a
custom kernel. Add this to the kernel config file and
build a new kernel:</para>
<programlisting>device bpf # Berkeley Packet Filter</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="mount-smb-share">
<para>How do I mount a disk from a &windows; machine that is
on my network, like smbmount in &linux;?</para>
</question>
<answer>
<para>Use the <application>SMBFS</application> toolset. It
includes a set of kernel modifications and a set of
userland programs. The programs and information are
available as &man.mount.smbfs.8; in the base
system.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="icmp-response-bw-limit">
<para>What are these messages about: <errorname>Limiting
icmp/open port/closed port response</errorname> in my
log files?</para>
</question>
<answer>
<para>This kernel message indicates that some activity is
provoking it to send a large amount of ICMP or TCP reset
(RST) responses. ICMP responses are
often generated as a result of attempted connections to
unused UDP ports. TCP resets are generated as a result of
attempted connections to unopened TCP ports. Among
others, these are the kinds of activities which may cause
these messages:</para>
<itemizedlist>
<listitem>
<para>Brute-force denial of service (DoS) attacks (as
opposed to single-packet attacks which exploit a
specific vulnerability).</para>
</listitem>
<listitem>
<para>Port scans which attempt to connect to a large
number of ports (as opposed to only trying a few
well-known ports).</para>
</listitem>
</itemizedlist>
<para>The first number in the message indicates how many
packets the kernel would have sent if the limit was not in
place, and the second indicates the limit. This limit
is controlled using
<varname>net.inet.icmp.icmplim</varname>. This example
sets the limit to <literal>300</literal>
packets per second:</para>
<screen>&prompt.root; <userinput>sysctl net.inet.icmp.icmplim=300</userinput></screen>
<para>To disable these messages
without disabling response
limiting, use
<varname>net.inet.icmp.icmplim_output</varname>
to disable the output:</para>
<screen>&prompt.root; <userinput>sysctl net.inet.icmp.icmplim_output=0</userinput></screen>
<para>Finally, to disable response limiting completely,
set <varname>net.inet.icmp.icmplim</varname> to
<literal>0</literal>. Disabling response limiting is
discouraged for the reasons listed above.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="unknown-hw-addr-format">
<para>What are these <errorname>arp: unknown hardware
address format</errorname> error messages?</para>
</question>
<answer>
<para>This means that some device on the local Ethernet is
using a MAC address in a format that &os; does not
recognize. This is probably caused by someone
experimenting with an Ethernet card somewhere else on the
network. This is most commonly seen on cable modem
networks. It is harmless, and should not affect the
performance of the &os; system.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="arp-wrong-iface">
<para>Why do I keep seeing messages like:
<errorname>192.168.0.10 is on
fxp1 but got reply from 00:15:17:67:cf:82 on
rl0</errorname>, and how do I disable it?</para>
</question>
<answer>
<para>Because a packet is coming from outside the network
unexpectedly. To disable them, set
<varname>net.link.ether.inet.log_arp_wrong_iface</varname>
to <literal>0</literal>.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="security">
<title>Security</title>
<qandaset>
<qandaentry>
<question xml:id="sandbox">
<para>What is a sandbox?</para>
</question>
<answer>
<para><quote>Sandbox</quote> is a security term. It can
mean two things:</para>
<itemizedlist>
<listitem>
<para>A process which is placed inside a set of virtual
walls that are designed to prevent someone who breaks
into the process from being able to break into the
wider system.</para>
<para>The process is only able to run inside the walls.
Since nothing the process does in regards to executing
code is supposed to be able to breach the walls, a
detailed audit of its code is not needed in order to
be able to say certain things about its
security.</para>
<para>The walls might be a user ID, for example.
This is the definition used in the &man.security.7;
and &man.named.8; man pages.</para>
<para>Take the <literal>ntalk</literal> service, for
example (see &man.inetd.8;). This service used to run
as user&nbsp;ID <systemitem
class="username">root</systemitem>. Now it runs as
user&nbsp;ID <systemitem
class="username">tty</systemitem>. The <systemitem
class="username">tty</systemitem> user is a sandbox
designed to make it more difficult for someone who has
successfully hacked into the system via
<literal>ntalk</literal> from being able to hack
beyond that user&nbsp;ID.</para>
</listitem>
<listitem>
<para>A process which is placed inside a simulation of
the machine. It means that someone who is able to
break into the process may believe that he can break
into the wider machine but is, in fact, only breaking
into a simulation of that machine and not modifying
any real data.</para>
<para>The most common way to accomplish this is to build
a simulated environment in a subdirectory and then run
the processes in that directory chrooted so that
<filename>/</filename> for that process is this
directory, not the real <filename>/</filename> of the
system).</para>
<para>Another common use is to mount an underlying file
system read-only and then create a file system layer
on top of it that gives a process a seemingly
writeable view into that file system. The process may
believe it is able to write to those files, but only
the process sees the effects &mdash; other processes
in the system do not, necessarily.</para>
<para>An attempt is made to make this sort of sandbox so
transparent that the user (or hacker) does not realize
that he is sitting in it.</para>
</listitem>
</itemizedlist>
<para>&unix; implements two core sandboxes. One is at the
process level, and one is at the userid level.</para>
<para>Every &unix; process is completely firewalled off from
every other &unix; process. One process cannot modify the
address space of another.</para>
<para>A &unix; process is owned by a particular userid. If
the user&nbsp;ID is not the <systemitem
class="username">root</systemitem> user, it serves to
firewall the process off from processes owned by other
users. The user&nbsp;ID is also used to firewall off
on-disk data.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="securelevel">
<para>What is securelevel?</para>
</question>
<answer>
<para><literal>securelevel</literal> is a security
mechanism implemented in the kernel. When the securelevel
is positive, the kernel restricts certain tasks; not even
the superuser (<systemitem
class="username">root</systemitem>) is allowed to do
them. The securelevel mechanism limits the ability
to:</para>
<itemizedlist>
<listitem>
<para>Unset certain file flags, such as
<literal>schg</literal> (the system immutable
flag).</para>
</listitem>
<listitem>
<para>Write to kernel memory via
<filename>/dev/mem</filename> and
<filename>/dev/kmem</filename>.</para>
</listitem>
<listitem>
<para>Load kernel modules.</para>
</listitem>
<listitem>
<para>Alter firewall rules.</para>
</listitem>
</itemizedlist>
<para>To check the status of the securelevel on a running
system:</para>
<screen>&prompt.root; <userinput>sysctl -n kern.securelevel</userinput></screen>
<para>The output contains the current value of the
securelevel. If it is greater than 0, at
least some of the securelevel's protections are
enabled.</para>
<para>The securelevel of a running system cannot be lowered
as this would defeat its purpose. If a task requires that
the securelevel be non-positive, change the
<varname>kern_securelevel</varname> and
<varname>kern_securelevel_enable</varname> variables in
<filename>/etc/rc.conf</filename> and reboot.</para>
<para>For more information on securelevel and the specific
things all the levels do, consult &man.init.8;.</para>
<warning>
<para>Securelevel is not a silver bullet; it has many
known deficiencies. More often than not, it provides a
false sense of security.</para>
<para>One of its biggest problems is that in order for it
to be at all effective, all files used in the boot
process up until the securelevel is set must be
protected. If an attacker can get the system to execute
their code prior to the securelevel being set (which
happens quite late in the boot process since some things
the system must do at start-up cannot be done at an
elevated securelevel), its protections are invalidated.
While this task of protecting all files used in the boot
process is not technically impossible, if it is
achieved, system maintenance will become a nightmare
since one would have to take the system down, at least
to single-user mode, to modify a configuration
file.</para>
<para>This point and others are often discussed on the
mailing lists, particularly the &a.security;.
Search the archives <link
xlink:href="&url.base;/search/index.html">here</link>
for an extensive discussion. A more fine-grained
mechanism is preferred.</para>
</warning>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="extra-named-port">
<para><application>BIND9</application>
(<command>named</command>) is listening on some
high-numbered ports. What is going on?</para>
</question>
<answer>
<para>BIND uses a random high-numbered port for outgoing
queries. Recent versions of it choose a new, random UDP
port for each query. This may cause problems for some
network configurations, especially if a firewall blocks
incoming UDP packets on particular ports. To
get past that firewall, try the
<literal>avoid-v4-udp-ports</literal> and
<literal>avoid-v6-udp-ports</literal> options to avoid
selecting random port numbers within a blocked
range.</para>
<warning>
<para>If a port number (like 53) is specified via the
<literal>query-source</literal> or
<literal>query-source-v6</literal> options in
<filename>/usr/local/etc/namedb/named.conf</filename>,
randomized
port selection will not be used. It is strongly
recommended that these options not be used to specify
fixed port numbers.</para>
</warning>
<para>Congratulations, by the way. It is good practice to
read &man.sockstat.1; output and notice odd
things!</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="sendmail-port-587">
<para>The <application>Sendmail</application> daemon is
listening on port 587 as well as the standard port 25!
What is going on?</para>
</question>
<answer>
<para>Recent versions of <application>Sendmail</application>
support a mail submission feature that runs over port 587.
This is not yet widely supported, but is growing in
popularity.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="toor-account">
<para>What is this UID 0 <systemitem
class="username">toor</systemitem> account? Have I been
compromised?</para>
</question>
<answer>
<para>Do not worry. <systemitem
class="username">toor</systemitem> is an
<quote>alternative</quote> superuser account, where toor
is root spelled backwards. It is intended to be used with
a non-standard shell so the default shell for <systemitem
class="username">root</systemitem> does not need to
change. This is important as shells which are not part of
the base distribution, but are instead installed from
ports or packages, are installed in
<filename>/usr/local/bin</filename> which, by default,
resides on a different file system. If <systemitem
class="username">root</systemitem>'s shell is located in
<filename>/usr/local/bin</filename> and the
file system
containing <filename>/usr/local/bin</filename>) is not
mounted, <systemitem
class="username">root</systemitem> will not be able to
log in to fix a problem and will have to reboot into
single-user mode in order to enter the path to a
shell.</para>
<para>Some people use <systemitem
class="username">toor</systemitem> for day-to-day
<systemitem class="username">root</systemitem> tasks with
a non-standard shell, leaving <systemitem
class="username">root</systemitem>, with a standard
shell, for single-user mode or emergencies. By default, a
user cannot log in using <systemitem
class="username">toor</systemitem> as it does not have a
password, so log in as <systemitem
class="username">root</systemitem> and set a password
for <systemitem class="username">toor</systemitem> before
using it to login.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="ppp">
<title>PPP</title>
<qandaset>
<qandaentry>
<question xml:id="userppp">
<para>I cannot make &man.ppp.8; work. What am I doing
wrong?</para>
</question>
<answer>
<para>First, read &man.ppp.8; and
the <link
xlink:href="&url.books.handbook;/ppp-and-slip.html#userppp">PPP
section of the Handbook</link>. To assist in
troubleshooting, enable logging with the
following command:</para>
<programlisting>set log Phase Chat Connect Carrier lcp ipcp ccp command</programlisting>
<para>This command may be typed at the &man.ppp.8; command
prompt or it may be entered at the start of the
<literal>default</literal> section
in <filename>/etc/ppp/ppp.conf</filename>. Make sure that
<filename>/etc/syslog.conf</filename> contains the lines
below and the file <filename>/var/log/ppp.log</filename>
exists:</para>
<programlisting>!ppp
*.* /var/log/ppp.log</programlisting>
<para>A lot about what is going can be learned from the log
file. Do not worry if it does not all make sense as
it may make sense to someone else.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-hangs">
<para>Why does &man.ppp.8; hang when I run it?</para>
</question>
<answer>
<para>This is usually because the hostname will not
resolve. The best way to fix this is to make sure that
<filename>/etc/hosts</filename> is read first by the
by ensuring that the <literal>hosts</literal> line is
listed first in <filename>/etc/host.conf</filename>.
Then, put an entry in <filename>/etc/hosts</filename> for
the local machine. If there is no local network, change
the <systemitem>localhost</systemitem> line:</para>
<programlisting>127.0.0.1 foo.example.com foo localhost</programlisting>
<para>Otherwise, add another entry for the host.
Consult the relevant manual pages for more details.</para>
<para>When finished, verify that this command is successful:
<command>ping -c1 `hostname`</command>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-nodial-auto">
<para>Why will &man.ppp.8; not dial in
<literal>-auto</literal> mode?</para>
</question>
<answer>
<para>First, check that a default route exists. This
command should display two entries:</para>
<programlisting>Destination Gateway Flags Refs Use Netif Expire
default 10.0.0.2 UGSc 0 0 tun0
10.0.0.2 10.0.0.1 UH 0 0 tun0</programlisting>
<para>If
a default route is not listed, make sure that the
<literal>HISADDR</literal> line has been added to
<filename>/etc/ppp/ppp.conf</filename>.</para>
<para>Another reason for the default route line being
missing is that a default
route has been added to <filename>/etc/rc.conf</filename>
and this line is missing
from <filename>/etc/ppp/ppp.conf</filename>:</para>
<programlisting>delete ALL</programlisting>
<para>If this is the case, go back to the <link
xlink:href="&url.books.handbook;/userppp.html#userppp-final">Final
System Configuration</link> section of the
Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="no-route-to-host">
<para>What does <errorname>No route to host</errorname>
mean?</para>
</question>
<answer>
<para>This error is usually because the following section
is missing in
<filename>/etc/ppp/ppp.linkup</filename>:</para>
<programlisting>MYADDR:
delete ALL
add 0 0 HISADDR</programlisting>
<para>This is only necessary for a dynamic IP address or
when the address of the default gateway is unknown. When
using interactive mode, the following can be typed in
after entering packet mode. Packet mode
is indicated by the capitalized <acronym>PPP</acronym> in
the prompt:</para>
<programlisting>delete ALL
add 0 0 HISADDR</programlisting>
<para>Refer to the <link
xlink:href="&url.books.handbook;/userppp.html#userppp-dynamicip">PPP
and Dynamic IP addresses</link> section of the Handbook
for further details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="connection-threeminutedrop">
<para>Why does my connection drop after about 3
minutes?</para>
</question>
<answer>
<para>The default PPP timeout is 3 minutes. This can be
adjusted with the following line:</para>
<programlisting>set timeout <replaceable>NNN</replaceable></programlisting>
<para>where <replaceable>NNN</replaceable> is the number of
seconds of inactivity before the connection is closed. If
<replaceable>NNN</replaceable> is zero, the connection is
never closed due to a timeout. It is possible to put this
command in <filename>ppp.conf</filename>, or to type it at
the prompt in interactive mode. It is also possible to
adjust it on the fly while the line is active by
connecting to <application>ppp</application>'s server
socket using &man.telnet.1; or &man.pppctl.8;. Refer to
the &man.ppp.8; man page for further details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-drop-heavy-load">
<para>Why does my connection drop under heavy load?</para>
</question>
<answer>
<para>If Link Quality Reporting (<acronym>LQR</acronym>) is
configured, it is possible that too many
<acronym>LQR</acronym> packets are lost between the &os;
system and the peer. &man.ppp.8; deduces that the line
must therefore be bad, and disconnects.
<acronym>LQR</acronym> is disabled by default and can be
enabled with the following line:</para>
<programlisting>enable lqr</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-drop-random">
<para>Why does my connection drop after a random amount of
time?</para>
</question>
<answer>
<para>Sometimes, on a noisy phone line or even on a line
with call waiting enabled, the modem may hang up because
it incorrectly thinks that it lost carrier.</para>
<para>There is a setting on most modems for determining how
tolerant it should be to temporary losses of carrier.
Refer to the modem manual for details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-hangs-random">
<para>Why does my connection hang after a random amount of
time?</para>
</question>
<answer>
<para>Many people experience hung connections with no
apparent explanation. The first thing to establish is
which side of the link is hung.</para>
<para>When using an external modem, try
using &man.ping.8; to see if the <acronym>TD</acronym>
light is flashing when data is transmitted. If it flashes
but the <acronym>RD</acronym> light does not, the
problem is with the remote end. If <acronym>TD</acronym>
does not flash, the problem is local. With an internal
modem, use the <literal>set
server</literal> command in
<filename>ppp.conf</filename>. When the hang occurs,
connect to &man.ppp.8; using &man.pppctl.8;. If the
network connection suddenly revives due to the activity on
the diagnostic socket, or if it will not
connect but the <literal>set socket</literal>
command succeeded at startup time, the problem is local.
If it can connect but things are still hung, enable local
logging with <literal>set log local async</literal>
and use &man.ping.8; from another window or terminal to
make use of the link. The async logging will show the
data being transmitted and received on the link. If data
is going out and not coming back, the problem is
remote.</para>
<para>Having established whether the problem is local or
remote, there are now two possibilities:</para>
<itemizedlist>
<listitem>
<para>If the problem is remote, read on entry <xref
linkend="ppp-remote-not-responding"/>.</para>
</listitem>
<listitem>
<para>If the problem is local, read on entry <xref
linkend="ppp-hung"/>.</para>
</listitem>
</itemizedlist>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-remote-not-responding">
<para>The remote end is not responding. What can I
do?</para>
</question>
<answer>
<para>There is very little that can be done about this.
Many ISPs will refuse to help users not running a
&microsoft; OS. Add <literal>enable lqr</literal> to
<filename>/etc/ppp/ppp.conf</filename>, allowing
&man.ppp.8; to detect the remote failure and hang up.
This detection is relatively slow and therefore not that
useful.</para>
<para>First, try disabling all local compression by adding
the following to the configuration:</para>
<programlisting>disable pred1 deflate deflate24 protocomp acfcomp shortseq vj
deny pred1 deflate deflate24 protocomp acfcomp shortseq vj</programlisting>
<para>Then reconnect to ensure that this makes no
difference. If things improve or if the problem is solved
completely, determine which setting makes the difference
through trial and error. This is good information for
the ISP, although it may make
it apparent that it is not a &microsoft; system.</para>
<para>Before contacting the ISP, enable async logging
locally and wait until the connection hangs again. This
may use up quite a bit of disk space. The last data read
from the port may be of interest. It is usually ASCII
data, and may even describe the problem (<errorname>Memory
fault</errorname>, <errorname>Core
dumped</errorname>).</para>
<para>If the ISP is helpful, they should be able to enable
logging on their end, then when the next link drop occurs,
they may be able to tell why their side is having a
problem.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-hung">
<para>&man.ppp.8; has hung. What can I do?</para>
</question>
<answer>
<para>In this case, rebuild &man.ppp.8; with
debugging information, and then use &man.gdb.1; to grab a
stack trace from the <application>ppp</application>
process that is stuck. To rebuild the
<application>ppp</application> utility with debugging
information, type:</para>
<screen>&prompt.root; <userinput>cd /usr/src/usr.sbin/ppp</userinput>
&prompt.root; <userinput>env DEBUG_FLAGS='-g' make clean</userinput>
&prompt.root; <userinput>env DEBUG_FLAGS='-g' make install</userinput></screen>
<para>Then, restart <application>ppp</application>
and wait until it hangs again. When the debug build of
<application>ppp</application> hangs, start
<application>gdb</application> on the stuck process by
typing:</para>
<screen>&prompt.root; <userinput>gdb ppp `pgrep ppp`</userinput></screen>
<para>At the <application>gdb</application> prompt,
use the <command>bt</command> or <command>where</command>
commands to get a stack trace. Save the output of the
<application>gdb</application> session, and
<quote>detach</quote> from the running process by typing
<command>quit</command>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-same-magic">
<para>I keep seeing errors about magic being the same. What
does it mean?</para>
</question>
<answer>
<para>Occasionally, just after connecting, there may be
messages in the log that say <errorname>Magic is
same</errorname>. Sometimes, these messages are
harmless, and sometimes one side or the other exits. Most
PPP implementations cannot survive this problem, and even
if the link seems to come up, there will be repeated
configure requests and configure acknowledgments in the
log file until &man.ppp.8; eventually gives up and closes
the connection.</para>
<para>This normally happens on server machines with slow
disks that are spawning a &man.getty.8; on the port, and
executing &man.ppp.8; from a login script or program after
login. There were reports of it happening consistently
when using slirp. The reason is that in the time taken
between &man.getty.8; exiting and &man.ppp.8; starting,
the client-side &man.ppp.8; starts sending Line Control
Protocol (LCP) packets. Because ECHO is still switched on
for the port on the server, the client &man.ppp.8; sees
these packets <quote>reflect</quote> back.</para>
<para>One part of the LCP negotiation is to establish a
magic number for each side of the link so that
<quote>reflections</quote> can be detected. The protocol
says that when the peer tries to negotiate the same magic
number, a NAK should be sent and a new magic number should
be chosen. During the period that the server port has
ECHO turned on, the client &man.ppp.8; sends LCP packets,
sees the same magic in the reflected packet and NAKs it.
It also sees the NAK reflect (which also means &man.ppp.8;
must change its magic). This produces a potentially
enormous number of magic number changes, all of which are
happily piling into the server's tty buffer. As soon as
&man.ppp.8; starts on the server, it is flooded with magic
number changes and almost immediately decides it has tried
enough to negotiate LCP and gives up. Meanwhile, the
client, who no longer sees the reflections, becomes happy
just in time to see a hangup from the server.</para>
<para>This can be avoided by allowing the peer to start
negotiating with the following line in
<filename>ppp.conf</filename>:</para>
<programlisting>set openmode passive</programlisting>
<para>This tells &man.ppp.8; to wait for the server to
initiate LCP negotiations. Some servers however may never
initiate negotiations. In this case, try
something like:</para>
<programlisting>set openmode active 3</programlisting>
<para>This tells &man.ppp.8; to be passive for 3 seconds,
and then to start sending LCP requests. If the peer
starts sending requests during this period, &man.ppp.8;
will immediately respond rather than waiting for the full
3 second period.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-lcp-constant">
<para>LCP negotiations continue until the connection is
closed. What is wrong?</para>
</question>
<answer>
<para>There is currently an implementation mis-feature in
&man.ppp.8; where it does not associate LCP, CCP &amp;
IPCP responses with their original requests. As a result,
if one PPP implementation is more than 6 seconds slower
than the other side, the other side will send two
additional LCP configuration requests. This is
fatal.</para>
<para>Consider two implementations,
<systemitem>A</systemitem> and <systemitem>B</systemitem>.
<systemitem>A</systemitem> starts sending LCP requests
immediately after connecting and
<systemitem>B</systemitem> takes 7 seconds to start. When
<systemitem>B</systemitem> starts,
<systemitem>A</systemitem> has sent 3 LCP REQs. We are
assuming the line has ECHO switched off, otherwise we
would see magic number problems as described in the
previous section. <systemitem>B</systemitem> sends a REQ,
then an ACK to the first of <systemitem>A</systemitem>'s
REQs. This results in <systemitem>A</systemitem> entering
the <acronym>OPENED</acronym> state and sending and ACK
(the first) back to <systemitem>B</systemitem>. In the
meantime, <systemitem>B</systemitem> sends back two more
ACKs in response to the two additional REQs sent by
<systemitem>A</systemitem> before
<systemitem>B</systemitem> started up.
<systemitem>B</systemitem> then receives the first ACK
from <systemitem>A</systemitem> and enters the
<acronym>OPENED</acronym> state.
<systemitem>A</systemitem> receives the second ACK from
<systemitem>B</systemitem> and goes back to the
<acronym>REQ-SENT</acronym> state, sending another (forth)
REQ as per the RFC. It then receives the third ACK and
enters the <acronym>OPENED</acronym> state. In the
meantime, <systemitem>B</systemitem> receives the forth
REQ from <systemitem>A</systemitem>, resulting in it
reverting to the <acronym>ACK-SENT</acronym> state and
sending another (second) REQ and (forth) ACK as per the
RFC. <systemitem>A</systemitem> gets the REQ, goes into
<acronym>REQ-SENT</acronym> and sends another REQ. It
immediately receives the following ACK and enters
<acronym>OPENED</acronym>.</para>
<para>This goes on until one side figures out that they are
getting nowhere and gives up.</para>
<para>The best way to avoid this is to configure one side to
be <literal>passive</literal> &mdash; that is, make one
side wait for the other to start negotiating. This can be
done with the following command:</para>
<programlisting>set openmode passive</programlisting>
<para>Care should be taken with this option. This command
can also be used to limit the amount of time that
&man.ppp.8; waits for the peer to begin
negotiations:</para>
<programlisting>set stopped <replaceable>N</replaceable></programlisting>
<para>Alternatively, the following command (where
<replaceable>N</replaceable> is the number of seconds to
wait before starting negotiations) can be used:</para>
<programlisting>set openmode active <replaceable>N</replaceable></programlisting>
<para>Check the manual page for details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-shell-test-lockup">
<para>Why does &man.ppp.8; lock up when I shell out to test
it?</para>
</question>
<answer>
<para>When using <command>shell</command> or
<command>!</command>, &man.ppp.8; executes a shell
or the passed arguments. The
<application>ppp</application> program will wait for the
command to complete before continuing. Any attempt to
use the PPP link while running the command will appear as
a frozen link. This is because &man.ppp.8; is
waiting for the command to complete.</para>
<para>To execute commands like this, use
<command>!bg</command> instead. This will execute the
given command in the background, and &man.ppp.8; can
continue to service the link.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-null-modem">
<para>Why does &man.ppp.8; over a null-modem cable never
exit?</para>
</question>
<answer>
<para>There is no way for &man.ppp.8; to automatically
determine that a direct connection has been dropped. This
is due to the lines that are used in a null-modem serial
cable. When using this sort of connection, LQR should
always be enabled with the following line:</para>
<programlisting>enable lqr</programlisting>
<para>LQR is accepted by default if negotiated by the
peer.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-auto-noreasondial">
<para>Why does &man.ppp.8; dial for no reason in
<option>-auto</option> mode?</para>
</question>
<answer>
<para>If &man.ppp.8; is dialing unexpectedly,
determine the cause, and set up dial filters to
prevent such dialing.</para>
<para>To determine the cause, use the following line:</para>
<programlisting>set log +tcp/ip</programlisting>
<para>This will log all traffic through the connection. The
next time the line comes up unexpectedly, the
reason will be logged with a convenient timestamp next to
it.</para>
<para>Next, disable dialing under these circumstances.
Usually, this sort of problem arises due to DNS lookups.
To prevent DNS lookups from establishing a connection
(this will <emphasis>not</emphasis> prevent &man.ppp.8;
from passing the packets through an established
connection), use the following:</para>
<programlisting>set dfilter 1 deny udp src eq 53
set dfilter 2 deny udp dst eq 53
set dfilter 3 permit 0/0 0/0</programlisting>
<para>This is not always suitable, as it will effectively
break demand-dial capabilities. Most programs
will need a DNS lookup before doing any other network
related things.</para>
<para>In the DNS case, try to determine what is actually
trying to resolve a host name. A lot of the time,
<application>Sendmail</application> is the culprit. Make
sure to configure <application>Sendmail</application> not
to do any DNS lookups in its configuration file. See the
section on <link
xlink:href="&url.books.handbook;/smtp-dialup.html">using
email with a dialup connection</link> in the &os;
Handbook for details. You may
also want to add the following line to
<filename>.mc</filename>:</para>
<programlisting>define(`confDELIVERY_MODE', `d')dnl</programlisting>
<para>This will make <application>Sendmail</application>
queue everything until the queue is run, usually,
every 30 minutes, or until a <command>sendmail
-q</command> is done, perhaps from
<filename>/etc/ppp/ppp.linkup</filename>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ccp-errors">
<para>What do these CCP errors mean?</para>
</question>
<answer>
<para>I keep seeing the following errors in my log
file:</para>
<programlisting>CCP: CcpSendConfigReq
CCP: Received Terminate Ack (1) state = Req-Sent (6)</programlisting>
<para>This is because &man.ppp.8; is trying to negotiate
Predictor1 compression, but the peer does not want to
negotiate any compression at all. The messages are
harmless, but can be silenced by disabling the
compression:</para>
<programlisting>disable pred1</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-connectionspeed">
<para>Why does &man.ppp.8; not log my connection
speed?</para>
</question>
<answer>
<para>To log all lines of the modem
conversation, enable the
following:</para>
<programlisting>set log +connect</programlisting>
<para>This will make &man.ppp.8; log everything up until the
last requested <quote>expect</quote> string.</para>
<para>To see the connect speed when using
PAP or CHAP,
make sure to configure &man.ppp.8; to
expect the whole CONNECT line, using something
like this:</para>
<programlisting>set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 4 \
\"\" ATZ OK-ATZ-OK ATDT\\T TIMEOUT 60 CONNECT \\c \\n"</programlisting>
<para>This gets the CONNECT, sends nothing, then expects a
line-feed, forcing &man.ppp.8; to read the whole CONNECT
response.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="ppp-ignores-backslash">
<para>Why does &man.ppp.8; ignore the <literal>\</literal>
character in my chat script?</para>
</question>
<answer>
<para>The <application>ppp</application> utility parses each
line in its configuration files so that it can interpret
strings such as <literal>set phone "123 456 789"</literal>
correctly and realize that the number is actually only
one argument. To specify a
<literal>&quot;</literal> character, escape it
using a backslash (<literal>\</literal>).</para>
<para>When the chat interpreter parses each argument, it
re-interprets the argument to find any special escape
sequences such as <literal>\P</literal> or
<literal>\T</literal>. As a result
of this double-parsing, remember to use the
correct number of escapes.</para>
<para>To actually send a <literal>\</literal>
character, do something
like:</para>
<programlisting>set dial "\"\" ATZ OK-ATZ-OK AT\\\\X OK"</programlisting>
<para>It will result in the following sequence:</para>
<programlisting>ATZ
OK
AT\X
OK</programlisting>
<para>Or:</para>
<programlisting>set phone 1234567
set dial "\"\" ATZ OK ATDT\\T"</programlisting>
<para>It will result in the following sequence:</para>
<programlisting>ATZ
OK
ATDT1234567</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="fcs-errors">
<para>What are FCS errors?</para>
</question>
<answer>
<para>FCS stands for Frame Check Sequence. Each PPP packet
has a checksum attached to ensure that the data being
received is the data being sent. If the FCS of an
incoming packet is incorrect, the packet is dropped and
the HDLC FCS count is increased. The HDLC error values
can be displayed using the <literal>show hdlc</literal>
command.</para>
<para>If the link is bad or if the serial driver is dropping
packets, it will produce the occasional FCS error.
This is not usually worth worrying about although it does
slow down the compression protocols substantially.</para>
<para>If the link freezes as soon as it connects and
produces a large number of FCS errors, make sure the modem
is not using software flow control (XON/XOFF). If the
link must use software flow control, use
<literal>set accmap 0x000a0000</literal> to
tell &man.ppp.8; to escape the <literal>^Q</literal> and
<literal>^S</literal> characters.</para>
<para>Another reason for too many FCS errors may be
that the remote end has stopped talking
<acronym>PPP</acronym>. In this case, enable
<literal>async</literal> logging to
determine if the incoming data is actually a login or
shell prompt. If it is a shell prompt at the remote
end, it is possible to terminate &man.ppp.8; without
dropping the line by using <command>close lcp</command>
followed by <command>term</command>) to reconnect to
the shell on the remote machine.</para>
<para>If nothing in the log file indicates why the link
was terminated, ask the remote
administrator or ISP why the session was
terminated.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="desperation">
<para>None of this helps &mdash; I am desperate! What can I
do?</para>
</question>
<answer>
<para>If all else fails, send the details of the error, the
configuration files, how &man.ppp.8; is being started, the
relevant parts of the log file, and the
output of <command>netstat -rn</command>, before and after
connecting, to the &a.questions;.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="serial">
<title>Serial Communications</title>
<para>This section answers common questions about serial
communications with &os;. PPP is covered in the <link
linkend="networking">Networking</link> section.</para>
<qandaset>
<qandaentry>
<question xml:id="multiport-serial-support">
<para>Which multi-port serial cards are supported by
&os;?</para>
</question>
<answer>
<para>There is a list of these in the <link
xlink:href="&url.books.handbook;/serial.html">Serial
Communications</link> chapter of the Handbook.</para>
<para>Most multi-port PCI cards that are based on 16550 or
clones are supported with no extra effort.</para>
<para>Some unnamed clone cards have also been known to work,
especially those that claim to be AST compatible.</para>
<para>Check &man.uart.4; and &man.sio.4; to get more
information on configuring such cards.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="serial-console-prompt">
<para>How do I get the boot: prompt to show on the serial
console?</para>
</question>
<answer>
<para>See <link
xlink:href="&url.books.handbook;/serialconsole-setup.html">this
section of the Handbook</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="found-serial">
<para>How do I tell if &os; found my serial ports or modem
cards?</para>
</question>
<answer>
<para>As the &os; kernel boots, it will probe for the serial
ports for which the kernel is configured.
Either watch the boot messages closely
or run this command after the system is up and
running:</para>
<screen>&prompt.user; <userinput>grep -E '^(sio|uart)[0-9]' &lt; /var/run/dmesg.boot</userinput>
sio0: &lt;16550A-compatible COM port&gt; port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0
sio0: type 16550A
sio1: &lt;16550A-compatible COM port&gt; port 0x2f8-0x2ff irq 3 on acpi0
sio1: type 16550A</screen>
<para>This example shows two serial ports. The first is on
IRQ4, port address
<literal>0x3f8</literal>, and has a 16550A-type UART chip.
The second uses the same kind of chip but is on
IRQ3 and is at port address
<literal>0x2f8</literal>. Internal modem cards are
treated just like serial ports, except that they
always have a modem attached to the
port.</para>
<para>The <filename>GENERIC</filename> kernel includes
support for two serial ports using the same IRQ and port
address settings in the above example. If these settings
are not right for the system, or if there are more modem
cards or serial ports than the kernel is
configured for, reconfigure using the instructions in
<link linkend="make-kernel">building a kernel</link>
for more details.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="access-serial-ports">
<para>How do I access the serial ports on &os;?</para>
</question>
<answer>
<para>The third serial port, <filename>sio2</filename>,
or <filename>COM3</filename>,
is on <filename>/dev/cuad2</filename> for dial-out
devices, and on <filename>/dev/ttyd2</filename> for
dial-in devices. What is the difference between these two
classes of devices?</para>
<para>When
opening <filename>/dev/ttydX</filename> in blocking mode,
a process will wait for the corresponding
<filename>cuadX</filename> device to become inactive, and
then wait for the carrier detect line to go active. When
the <filename>cuadX</filename> device is opened, it makes
sure the serial port is not already in use by the
<filename>ttydX</filename> device. If the port is
available, it steals it from the
<filename>ttydX</filename> device. Also, the
<filename>cuadX</filename> device does not care about
carrier detect. With this scheme and an auto-answer
modem, remote users can log in and local users can still
dial out with the same modem and the system will take care
of all the conflicts.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="enable-multiport-serial">
<para>How do I enable support for a multi-port serial
card?</para>
</question>
<answer>
<para>The section on kernel configuration provides
information about configuring the kernel. For a
multi-port serial card, place an &man.sio.4; line for each
serial port on the card in the &man.device.hints.5; file.
But place the IRQ specifiers on only one of the entries.
All of the ports on the card should share one IRQ. For
consistency, use the last serial port to specify the IRQ.
Also, specify the following option in the kernel
configuration file:</para>
<programlisting>options COM_MULTIPORT</programlisting>
<para>The following <filename>/boot/device.hints</filename>
example is for an AST 4-port serial card on
IRQ&nbsp;12:</para>
<programlisting>hint.sio.4.at="isa"
hint.sio.4.port="0x2a0"
hint.sio.4.flags="0x701"
hint.sio.5.at="isa"
hint.sio.5.port="0x2a8"
hint.sio.5.flags="0x701"
hint.sio.6.at="isa"
hint.sio.6.port="0x2b0"
hint.sio.6.flags="0x701"
hint.sio.7.at="isa"
hint.sio.7.port="0x2b8"
hint.sio.7.flags="0x701"
hint.sio.7.irq="12"</programlisting>
<para>The flags indicate that the master port has minor
number <literal>7</literal> (<literal>0x700</literal>),
and all the ports share an IRQ
(<literal>0x001</literal>).</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="default-serial-params">
<para>Can I set the default serial parameters for a
port?</para>
</question>
<answer>
<para>See the <link
xlink:href="&url.books.handbook;/serial.html#serial-hw-config">Serial
Communications</link> section in the &os;
Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="enable-dialup">
<para>How can I enable dialup logins on my modem?</para>
</question>
<answer>
<para>Refer to the section about <link
xlink:href="&url.books.handbook;/dialup.html">Dial-in
Services</link> in the &os; Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="dumb-terminal">
<para>How can I connect a dumb terminal to my &os;
box?</para>
</question>
<answer>
<para>This information is in the <link
xlink:href="&url.books.handbook;/term.html">Terminals</link>
section of the &os; Handbook.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="cannot-tip">
<para>Why can I not run <command>tip</command> or
<command>cu</command>?</para>
</question>
<answer>
<para>The built-in &man.tip.1; and
&man.cu.1; utilities can only access the
<filename>/var/spool/lock</filename> directory via user
<systemitem class="username">uucp</systemitem> and group
<systemitem class="groupname">dialer</systemitem>.
Use the <systemitem
class="groupname">dialer</systemitem> group to control
who has access to the modem or remote systems by adding
user accounts to <systemitem
class="groupname">dialer</systemitem>.</para>
<para>Alternatively, everyone can be configured to run
&man.tip.1; and &man.cu.1; by typing:</para>
<screen>&prompt.root; <userinput>chmod 4511 /usr/bin/cu</userinput>
&prompt.root; <userinput>chmod 4511 /usr/bin/tip</userinput></screen>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="misc">
<title>Miscellaneous Questions</title>
<qandaset>
<qandaentry>
<question xml:id="more-swap">
<para>&os; uses a lot of swap space even when the computer
has free memory left. Why?</para>
</question>
<answer>
<para>&os; will proactively move entirely idle, unused pages
of main memory into swap in order to make more main memory
available for active use. This heavy use of swap is
balanced by using the extra free memory for
caching.</para>
<para>Note that while &os; is proactive in this regard, it
does not arbitrarily decide to swap pages when the system
is truly idle. Thus, the system will not be all
paged out after leaving it
idle overnight.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="top-freemem">
<para>Why does <command>top</command> show very little free
memory even when I have very few programs running?</para>
</question>
<answer>
<para>The simple answer is that free memory is wasted
memory. Any memory that programs do not actively
allocate is used within the &os; kernel as disk cache.
The values shown by &man.top.1; labeled as
<literal>Inact</literal>, <literal>Cache</literal>, and
<literal>Buf</literal> are all cached data at different
aging levels. This cached data means the system does not
have to access a slow disk again for data it has accessed
recently, thus increasing overall performance. In
general, a low value shown for <literal>Free</literal>
memory in &man.top.1; is good, provided it is not
<emphasis>very</emphasis> low.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="chmod-symlinks">
<para>Why will <command>chmod</command> not change the
permissions on symlinks?</para>
</question>
<answer>
<para>Symlinks do not have permissions, and by default,
&man.chmod.1; will follow symlinks to change the
permissions on the source file, if possible. For
the file, <filename>foo</filename> with a symlink named
<filename>bar</filename>, this command
will always succeed.</para>
<screen>&prompt.user; <userinput>chmod g-w bar</userinput></screen>
<para>However, the permissions on <filename>bar</filename>
will not have changed.</para>
<para>When changing modes of the file hierarchies rooted in
the files instead of the files themselves, use
either <option>-H</option> or <option>-L</option> together
with <option>-R</option> to make this work. See
&man.chmod.1; and &man.symlink.7; for more
information.</para>
<warning>
<para><option>-R</option> does a
<emphasis>recursive</emphasis> &man.chmod.1;. Be
careful about specifying directories or symlinks to
directories to &man.chmod.1;. To change the
permissions of a directory referenced by a symlink, use
&man.chmod.1; without any options and follow the symlink
with a trailing slash (<filename>/</filename>). For
example, if <filename>foo</filename> is a symlink to
directory <filename>bar</filename>, to
change the permissions of <filename>foo</filename>
(actually <filename>bar</filename>), do
something like:</para>
<screen>&prompt.user; <userinput>chmod 555 foo/</userinput></screen>
<para>With the trailing slash, &man.chmod.1; will follow
the symlink, <filename>foo</filename>, to change the
permissions of the directory,
<filename>bar</filename>.</para>
</warning>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="dos-binaries">
<para>Can I run DOS binaries under &os;?</para>
</question>
<answer>
<para>Yes. A DOS emulation program,
<package>emulators/doscmd</package>, is available in the
&os; Ports Collection.</para>
<para>If <application>doscmd</application> will not suffice,
<package>emulators/pcemu</package>
emulates an 8088 and enough BIOS services to run many DOS
text-mode applications. It requires the X Window
System.</para>
<para>The Ports Collection also has
<package>emulators/dosbox</package>. The main focus of
this application is emulating old DOS games using the
local file system for files.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="translation">
<para>What do I need to do to translate a &os; document into
my native language?</para>
</question>
<answer>
<para>See the <link
xlink:href="&url.books.fdp-primer;/translations.html">Translation
<acronym>FAQ</acronym></link> in the &os; Documentation Project
Primer.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="freebsd-mail-bounces">
<para>Why does my email to any address at <systemitem
class="fqdomainname">FreeBSD.org</systemitem>
bounce?</para>
</question>
<answer>
<para>The <systemitem
class="fqdomainname">FreeBSD.org</systemitem> mail
system implements some
<application>Postfix</application> checks on incoming mail
and rejects mail that is either from misconfigured relays
or otherwise appears likely to be spam. Some of the
specific requirements are: </para>
<itemizedlist>
<listitem>
<para>The IP address of the SMTP client must
"reverse-resolve" to a forward confirmed
hostname.</para>
</listitem>
<listitem>
<para>The fully-qualified hostname given in the
SMTP conversation (either HELO or EHLO) must resolve
to the IP address of the client.</para>
</listitem>
</itemizedlist>
<para>Other advice to help mail reach its destination
include:</para>
<itemizedlist>
<listitem>
<para>Mail should be sent in plain text, and messages
sent to mailing lists should generally be no more than
200KB in length.</para>
</listitem>
<listitem>
<para>Avoid excessive cross posting. Choose
<emphasis>one</emphasis> mailing list which seems most
relevant and send it there.</para>
</listitem>
</itemizedlist>
<para>If you still have trouble with email infrastructure at
<systemitem class="fqdomainname">FreeBSD.org</systemitem>,
send a note with the details to
<email>postmaster@freebsd.org</email>; Include a
date/time interval so that logs may be reviewed &mdash;
and note that we only keep one week's worth of mail logs.
(Be sure to specify the time zone or offset from
UTC.)</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="free-account">
<para>Where can I find a free &os; account?</para>
</question>
<answer>
<para>While &os; does not provide open access to any of
their servers, others do provide open access &unix;
systems. The charge varies and limited services may be
available.</para>
<para><link xlink:href="http://www.arbornet.org/">Arbornet,
Inc</link>, also known as <emphasis>M-Net</emphasis>,
has been providing open access to &unix; systems since
1983. Starting on an Altos running System III, the site
switched to BSD/OS in 1991. In June of 2000, the site
switched again to &os;. <emphasis>M-Net</emphasis> can be
accessed via <application>telnet</application> and
<application>SSH</application> and provides basic access
to the entire &os; software suite. However, network
access is limited to members and patrons who donate to the
system, which is run as a non-profit organization.
<emphasis>M-Net</emphasis> also provides an bulletin board
system and interactive chat.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="daemon-name">
<para>What is the cute little red guy's name?</para>
</question>
<answer>
<para>He does not have one, and is just called <quote>the
BSD daemon</quote>. If you insist upon using a name,
call him <quote>beastie</quote>. Note that
<quote>beastie</quote> is pronounced
<quote>BSD</quote>.</para>
<para>More about the BSD daemon is available on his <link
xlink:href="http://www.mckusick.com/beastie/index.html">home
page</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="use-beastie">
<para>Can I use the BSD daemon image?</para>
</question>
<answer>
<para>Perhaps. The BSD daemon is copyrighted by Marshall
Kirk McKusick. Check his <link
xlink:href="http://www.mckusick.com/beastie/mainpage/copyright.html">Statement
on the Use of the BSD Daemon Figure</link> for detailed
usage terms.</para>
<para>In summary, the image can be used in a tasteful
manner, for personal use, so long as appropriate credit
is given. Before using the logo commercially, contact
&a.mckusick.email; for permission. More details are
available on the <link
xlink:href="http://www.mckusick.com/beastie/index.html">BSD
Daemon's home page</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="daemon-images">
<para>Do you have any BSD daemon images I could use?</para>
</question>
<answer>
<para>Xfig and eps drawings are available under
<filename>/usr/share/examples/BSD_daemon/</filename>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="glossary">
<para>I have seen an acronym or other term on the mailing
lists and I do not understand what it means. Where should
I look?</para>
</question>
<answer>
<para>Refer to the <link
xlink:href="&url.books.handbook;/freebsd-glossary.html">&os;
Glossary</link>.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="bikeshed-painting">
<para>Why should I care what color the bikeshed is?</para>
</question>
<answer>
<para>The really, really short answer is that you should
not. The somewhat longer answer is that just because you
are capable of building a bikeshed does not mean you
should stop others from building one just because you do
not like the color they plan to paint it. This is a
metaphor indicating that you need not argue about every
little feature just because you know enough to do so.
Some people have commented that the amount of noise
generated by a change is inversely proportional to the
complexity of the change.</para>
<para>The longer and more complete answer is that after a
very long argument about whether &man.sleep.1; should take
fractional second arguments, &a.phk.email; posted a long
message entitled <quote><link
xlink:href="http://www.bikeshed.com">A
bike shed (any color will do) on greener
grass...</link></quote>. The appropriate portions of
that message are quoted below.</para>
<blockquote>
<attribution>&a.phk.email; on &a.hackers.name;, October 2,
1999</attribution>
<para><quote>What is it about this bike shed?</quote>
Some of you have asked me.</para>
<para>It is a long story, or rather it is an old story,
but it is quite short actually. C. Northcote Parkinson
wrote a book in the early 1960s, called
<quote>Parkinson's Law</quote>, which contains a lot of
insight into the dynamics of management.</para>
<para><emphasis>[snip a bit of commentary on the
book]</emphasis></para>
<para>In the specific example involving the bike shed, the
other vital component is an atomic power-plant, I guess
that illustrates the age of the book.</para>
<para>Parkinson shows how you can go into the board of
directors and get approval for building a multi-million
or even billion dollar atomic power plant, but if you
want to build a bike shed you will be tangled up in
endless discussions.</para>
<para>Parkinson explains that this is because an atomic
plant is so vast, so expensive and so complicated that
people cannot grasp it, and rather than try, they fall
back on the assumption that somebody else checked all
the details before it got this far. Richard P. Feynmann
gives a couple of interesting, and very much to the
point, examples relating to Los Alamos in his
books.</para>
<para>A bike shed on the other hand. Anyone can build one
of those over a weekend, and still have time to watch
the game on TV. So no matter how well prepared, no
matter how reasonable you are with your proposal,
somebody will seize the chance to show that he is doing
his job, that he is paying attention, that he is
<emphasis>here</emphasis>.</para>
<para>In Denmark we call it <quote>setting your
fingerprint</quote>. It is about personal pride and
prestige, it is about being able to point somewhere and
say <quote>There! <emphasis>I</emphasis> did
that.</quote> It is a strong trait in politicians, but
present in most people given the chance. Just think
about footsteps in wet cement.</para>
</blockquote>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="funnies">
<title>The &os; Funnies</title>
<qandaset>
<qandaentry>
<question xml:id="very-very-cool">
<para>How cool is &os;?</para>
</question>
<answer>
<para>Q. Has anyone done any temperature testing while
running &os;? I know &linux; runs cooler than DOS, but
have never seen a mention of &os;. It seems to run really
hot.</para>
<para>A. No, but we have done numerous taste tests on
blindfolded volunteers who have also had 250 micrograms of
LSD-25 administered beforehand. 35% of the volunteers
said that &os; tasted sort of orange, whereas &linux;
tasted like purple haze. Neither group mentioned any
significant variances in temperature. We eventually had
to throw the results of this survey out entirely anyway
when we found that too many volunteers were wandering out
of the room during the tests, thus skewing the results.
We think most of the volunteers are at Apple now, working
on their new <quote>scratch and sniff</quote> GUI. It is
a funny old business we are in!</para>
<para>Seriously, &os; uses the <acronym>HLT</acronym> (halt)
instruction when the system is idle thus lowering its
energy consumption and therefore the heat it generates.
Also if you have <acronym>ACPI</acronym> (Advanced
Configuration and Power Interface) configured, then &os;
can also put the CPU into a low power mode.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="letmeoutofhere">
<para>Who is scratching in my memory banks??</para>
</question>
<answer>
<para>Q. Is there anything <quote>odd</quote> that &os;
does when compiling the kernel which would cause the
memory to make a scratchy sound? When compiling (and for
a brief moment after recognizing the floppy drive upon
startup, as well), a strange scratchy sound emanates from
what appears to be the memory banks.</para>
<para>A. Yes! You will see frequent references to
<quote>daemons</quote> in the BSD documentation, and what
most people do not know is that this refers to genuine,
non-corporeal entities that now possess your computer.
The scratchy sound coming from your memory is actually
high-pitched whispering exchanged among the daemons as
they best decide how to deal with various system
administration tasks.</para>
<para>If the noise gets to you, a good <command>fdisk
/mbr</command> from DOS will get rid of them, but do not
be surprised if they react adversely and try to stop you.
In fact, if at any point during the exercise you hear the
satanic voice of Bill Gates coming from the built-in
speaker, take off running and do not ever look back!
Freed from the counterbalancing influence of the BSD
daemons, the twin demons of DOS and &windows; are often
able to re-assert total control over your machine to the
eternal damnation of your soul. Now that you know, given
a choice you would probably prefer to get used to the
scratchy noises, no?</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="changing-lightbulbs">
<para>How many &os; hackers does it take to change a
lightbulb?</para>
</question>
<answer>
<para>One thousand, one hundred and sixty-nine:</para>
<para>Twenty-three to complain to -CURRENT about the lights
being out;</para>
<para>Four to claim that it is a configuration problem, and
that such matters really belong on -questions;</para>
<para>Three to submit PRs about it, one of which is misfiled
under doc and consists only of <quote>it's
dark</quote>;</para>
<para>One to commit an untested lightbulb which breaks
buildworld, then back it out five minutes later;</para>
<para>Eight to flame the PR originators for not including
patches in their PRs;</para>
<para>Five to complain about buildworld being broken;</para>
<para>Thirty-one to answer that it works for them, and they
must have updated at a bad time;</para>
<para>One to post a patch for a new lightbulb to
-hackers;</para>
<para>One to complain that he had patches for this three
years ago, but when he sent them to -CURRENT they were
just ignored, and he has had bad experiences with the PR
system; besides, the proposed new lightbulb is
non-reflexive;</para>
<para>Thirty-seven to scream that lightbulbs do not belong
in the base system, that committers have no right to do
things like this without consulting the Community, and
WHAT IS -CORE DOING ABOUT IT!?</para>
<para>Two hundred to complain about the color of the bicycle
shed;</para>
<para>Three to point out that the patch breaks
&man.style.9;;</para>
<para>Seventeen to complain that the proposed new lightbulb
is under GPL;</para>
<para>Five hundred and eighty-six to engage in a flame war
about the comparative advantages of the GPL, the BSD
license, the MIT license, the NPL, and the personal
hygiene of unnamed FSF founders;</para>
<para>Seven to move various portions of the thread to -chat
and -advocacy;</para>
<para>One to commit the suggested lightbulb, even though it
shines dimmer than the old one;</para>
<para>Two to back it out with a furious flame of a commit
message, arguing that &os; is better off in the dark than
with a dim lightbulb;</para>
<para>Forty-six to argue vociferously about the backing out
of the dim lightbulb and demanding a statement from
-core;</para>
<para>Eleven to request a smaller lightbulb so it will fit
their Tamagotchi if we ever decide to port &os; to that
platform;</para>
<para>Seventy-three to complain about the SNR on -hackers
and -chat and unsubscribe in protest;</para>
<para>Thirteen to post <quote>unsubscribe</quote>,
<quote>How do I unsubscribe?</quote>, or <quote>Please
remove me from the list</quote>, followed by the usual
footer;</para>
<para>One to commit a working lightbulb while everybody is
too busy flaming everybody else to notice;</para>
<para>Thirty-one to point out that the new lightbulb would
shine 0.364% brighter if compiled with TenDRA (although it
will have to be reshaped into a cube), and that &os;
should therefore switch to TenDRA instead of GCC;</para>
<para>One to complain that the new lightbulb lacks
fairings;</para>
<para>Nine (including the PR originators) to ask <quote>what
is MFC?</quote>;</para>
<para>Fifty-seven to complain about the lights being out two
weeks after the bulb has been changed.</para>
<para><emphasis>&a.nik.email; adds:</emphasis></para>
<para><emphasis>I was laughing quite hard at
this.</emphasis></para>
<para><emphasis>And then I thought, <quote>Hang on,
shouldn't there be '1 to document it.' in that list
somewhere?</quote></emphasis></para>
<para><emphasis>And then I was enlightened
:-)</emphasis></para>
<para><emphasis>&a.tabthorpe.email;</emphasis> says:
<quote>None, <emphasis>real</emphasis> &os; hackers are
not afraid of the dark!</quote></para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="dev-null">
<para>Where does data written to
<filename>/dev/null</filename> go?</para>
</question>
<answer>
<para>It goes into a special data sink in the CPU where it
is converted to heat which is vented through the heatsink
/ fan assembly. This is why CPU cooling is increasingly
important; as people get used to faster processors, they
become careless with their data and more and more of it
ends up in <filename>/dev/null</filename>, overheating
their CPUs. If you delete <filename>/dev/null</filename>
(which effectively disables the CPU data sink) your CPU
may run cooler but your system will quickly become
constipated with all that excess data and start to behave
erratically. If you have a fast network connection you
can cool down your CPU by reading data out of
<filename>/dev/random</filename> and sending it off
somewhere; however you run the risk of overheating your
network connection and <filename>/</filename> or angering
your ISP, as most of the data will end up getting
converted to heat by their equipment, but they generally
have good cooling, so if you do not overdo it you should
be OK.</para>
<para><emphasis>Paul Robinson adds:</emphasis></para>
<para>There are other methods. As every good sysadmin
knows, it is part of standard practice to send data to the
screen of interesting variety to keep all the pixies that
make up your picture happy. Screen pixies (commonly
mis-typed or re-named as <quote>pixels</quote>) are
categorized by the type of hat they wear (red, green or
blue) and will hide or appear (thereby showing the color
of their hat) whenever they receive a little piece of
food. Video cards turn data into pixie-food, and then
send them to the pixies &mdash; the more expensive the
card, the better the food, so the better behaved the
pixies are. They also need constant stimulation &mdash;
this is why screen savers exist.</para>
<para>To take your suggestions further, you could just throw
the random data to console, thereby letting the pixies
consume it. This causes no heat to be produced at all,
keeps the pixies happy and gets rid of your data quite
quickly, even if it does make things look a bit messy on
your screen.</para>
<para>Incidentally, as an ex-admin of a large ISP who
experienced many problems attempting to maintain a stable
temperature in a server room, I would strongly discourage
people sending the data they do not want out to the
network. The fairies who do the packet switching and
routing get annoyed by it as well.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="punk-my-friend">
<para>My colleague sits at the computer too much, how
can I prank her?</para>
</question>
<answer>
<para>Install <package role="port">games/sl</package> and
wait for her to mistype <userinput>sl</userinput> for
<command>ls</command>.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="advanced">
<title>Advanced Topics</title>
<qandaset>
<qandaentry>
<question xml:id="learn-advanced">
<para>How can I learn more about &os;'s internals?</para>
</question>
<answer>
<para>See the <link
xlink:href="&url.books.arch-handbook;">&os;
Architecture Handbook</link>.</para>
<para>Additionally, much general &unix; knowledge is
directly applicable to &os;.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="how-to-contribute">
<para>How can I contribute to &os;?</para>
</question>
<answer>
<para>See the article on <link
xlink:href="&url.articles.contributing;/article.html">Contributing
to &os;</link> for specific advice on how to do this.
Assistance is more than welcome!</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="define-snap-release">
<para>What are snapshots and releases?</para>
</question>
<answer>
<para>There are currently &rel.numbranch; active/semi-active
branches in the &os; <link
xlink:href="http://svnweb.FreeBSD.org/base/">Subversion
Repository</link>. (Earlier branches are only changed
very rarely, which is why there are only &rel.numbranch;
active branches of development):</para>
<itemizedlist>
<listitem>
<para>&rel2.releng; AKA
&rel2.stable;</para>
</listitem>
<listitem>
<para>&rel.releng; AKA
&rel.stable;</para>
</listitem>
<listitem>
<para>&rel.head.releng; AKA
<emphasis>-CURRENT</emphasis> AKA
&rel.head;</para>
</listitem>
</itemizedlist>
<para><literal>HEAD</literal> is not an actual branch tag.
It is a symbolic constant for
the current, non-branched development
stream known as
<emphasis>-CURRENT</emphasis>.</para>
<para>Right now, <emphasis>-CURRENT</emphasis> is the
&rel.head.relx; development stream; the &rel.stable;
branch, &rel.releng;, forked off from
<emphasis>-CURRENT</emphasis> in &rel.relengdate; and the
&rel2.stable; branch, &rel2.releng;, forked off from
<emphasis>-CURRENT</emphasis> in &rel2.relengdate;.</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="submitting-kernel-extensions">
<para>I have written a kernel extension, who do I send it
to?</para>
</question>
<answer>
<para>Take a look at the article on <link
xlink:href="&url.articles.contributing;/article.html">Contributing
to &os;</link> to learn how to submit code.</para>
<para>And thanks for the thought!</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="kernel-panic-troubleshooting">
<para>How can I make the most of the data I see when my
kernel panics?</para>
</question>
<answer>
<para>Here is typical kernel panic:</para>
<programlisting>Fatal trap 12: page fault while in kernel mode
fault virtual address = 0x40
fault code = supervisor read, page not present
instruction pointer = 0x8:0xf014a7e5
stack pointer = 0x10:0xf4ed6f24
frame pointer = 0x10:0xf4ed6f28
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, def32 1, gran 1
processor eflags = interrupt enabled, resume, IOPL = 0
current process = 80 (mount)
interrupt mask =
trap number = 12
panic: page fault</programlisting>
<para>This message is not enough. While the instruction
pointer value is important, it is also configuration
dependent as it varies depending on the kernel image.
If it is a <filename>GENERIC</filename> kernel
image from one of the snapshots, it is possible for
somebody else to track down the offending function, but
for a custom kernel, only you can tell us where the fault
occurred.</para>
<para>To proceed:</para>
<procedure>
<step>
<para>Write down the instruction pointer value. Note
that the <literal>0x8:</literal> part at the beginning
is not significant in this case: it is the
<literal>0xf0xxxxxx</literal> part that we
want.</para>
</step>
<step>
<para>When the system reboots, do the following:</para>
<screen>&prompt.user; <userinput>nm -n kernel.that.caused.the.panic | grep f0xxxxxx</userinput></screen>
<para>where <literal>f0xxxxxx</literal> is the
instruction pointer value. The odds are you will not
get an exact match since the symbols in the kernel
symbol table are for the entry points of functions and
the instruction pointer address will be somewhere
inside a function, not at the start. If you do not
get an exact match, omit the last digit from the
instruction pointer value and try again:</para>
<screen>&prompt.user; <userinput>nm -n kernel.that.caused.the.panic | grep f0xxxxx</userinput></screen>
<para>If that does not yield any results, chop off
another digit. Repeat until there is some sort of
output. The result will be a possible list of
functions which caused the panic. This is a less than
exact mechanism for tracking down the point of
failure, but it is better than nothing.</para>
</step>
</procedure>
<para>However, the best way to track down the cause of a
panic is by capturing a crash dump, then using
&man.kgdb.1; to generate a stack trace on the crash
dump.</para>
<para>In any case, the method is this:</para>
<procedure>
<step>
<para>Make sure that the following line is included in
the kernel configuration file:</para>
<programlisting>makeoptions DEBUG=-g # Build kernel with gdb(1) debug symbols</programlisting>
</step>
<step>
<para>Change to the <filename>/usr/src</filename>
directory:</para>
<screen>&prompt.root; <userinput>cd /usr/src</userinput></screen>
</step>
<step>
<para>Compile the kernel:</para>
<screen>&prompt.root; <userinput>make buildkernel KERNCONF=<replaceable>MYKERNEL</replaceable></userinput></screen>
</step>
<step>
<para>Wait for &man.make.1; to finish compiling.</para>
</step>
<step>
<screen>&prompt.root; <userinput>make installkernel KERNCONF=MYKERNEL</userinput></screen>
</step>
<step>
<para>Reboot.</para>
</step>
</procedure>
<note>
<para>If <varname>KERNCONF</varname> is not included,
the <filename>GENERIC</filename> kernel will instead
be built and installed.</para>
</note>
<para>The &man.make.1; process will have built two kernels.
<filename>/usr/obj/usr/src/sys/MYKERNEL/kernel</filename>
and
<filename>/usr/obj/usr/src/sys/MYKERNEL/kernel.debug</filename>.
<filename>kernel</filename> was installed as
<filename>/boot/kernel/kernel</filename>, while
<filename>kernel.debug</filename> can be used as the
source of debugging symbols for &man.kgdb.1;.</para>
<para>To capture a crash dump, edit
<filename>/etc/rc.conf</filename> and set
<literal>dumpdev</literal> to point to either the swap
partition or <literal>AUTO</literal>. This will cause the
&man.rc.8; scripts to use the &man.dumpon.8; command to
enable crash dumps. This command can also be run
manually. After a panic, the crash dump can be recovered
using &man.savecore.8;; if <literal>dumpdev</literal> is
set in <filename>/etc/rc.conf</filename>, the &man.rc.8;
scripts will run &man.savecore.8; automatically and put
the crash dump in <filename>/var/crash</filename>.</para>
<note>
<para>&os; crash dumps are usually the same size as
physical RAM. Therefore, make sure there is enough
space in <filename>/var/crash</filename> to hold the
dump. Alternatively, run &man.savecore.8; manually
and have it recover the crash dump to another directory
with more room. It is possible to limit the
size of the crash dump by using <literal>options
MAXMEM=N</literal> where
<replaceable>N</replaceable> is the size of kernel's
memory usage in KBs. For example, for 1&nbsp;GB
of RAM, limit the kernel's memory usage to
128&nbsp;MB, so that the crash dump size
will be 128&nbsp;MB instead of 1&nbsp;GB.</para>
</note>
<para>Once the crash dump has been recovered , get a
stack trace as follows:</para>
<screen>&prompt.user; <userinput>kgdb /usr/obj/usr/src/sys/MYKERNEL/kernel.debug /var/crash/vmcore.0</userinput>
<prompt>(kgdb)</prompt> <userinput>backtrace</userinput></screen>
<para>Note that there may be several screens worth of
information. Ideally, use &man.script.1; to
capture all of them. Using the unstripped kernel image
with all the debug symbols should show the exact line of
kernel source code where the panic occurred. The stack
trace is usually read from the bottom up to trace
the exact sequence of events that lead to the crash.
&man.kgdb.1; can also be used to print out the contents of
various variables or structures to examine the system
state at the time of the crash.</para>
<tip>
<para>If a second computer is available, &man.kgdb.1; can
be configured to do remote debugging, including setting
breakpoints and single-stepping through the kernel
code.</para>
</tip>
<note>
<para>If <literal>DDB</literal> is enabled and the
kernel drops into the debugger, a panic
and a crash dump can be forced by typing
<literal>panic</literal> at the <literal>ddb</literal>
prompt. It may stop in the debugger again during the
panic phase. If it does, type
<literal>continue</literal> and it will finish the crash
dump.</para>
</note>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="dlsym-failure">
<para>Why has <function>dlsym()</function> stopped working
for ELF executables?</para>
</question>
<answer>
<para>The ELF toolchain does not, by default, make the
symbols defined in an executable visible to the dynamic
linker. Consequently <function>dlsym()</function>
searches on handles obtained from calls to
<function>dlopen(NULL, flags)</function> will fail to find
such symbols.</para>
<para>To search, using
<function>dlsym()</function>, for symbols present in the
main executable of a process, link the
executable using the <option>--export-dynamic</option>
option to the ELF linker (&man.ld.1;).</para>
</answer>
</qandaentry>
<qandaentry>
<question xml:id="change-kernel-address-space">
<para>How can I increase or reduce the kernel address space
on i386?</para>
</question>
<answer>
<para>By default, the kernel address space is 1&nbsp;GB
(2&nbsp;GB for PAE) for i386. When running a
network-intensive server or using
ZFS, this will probably not be
enough.</para>
<para>Add the following line to the kernel configuration
file to increase available space and rebuild the
kernel:</para>
<programlisting>options KVA_PAGES=<replaceable>N</replaceable></programlisting>
<para>To find the correct value of
<replaceable>N</replaceable>, divide the desired address
space size (in megabytes) by four. (For example, it is
<literal>512</literal> for 2&nbsp;GB.)</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
<chapter xml:id="acknowledgments">
<title>Acknowledgments</title>
<para>This innocent little Frequently Asked Questions document has
been written, rewritten, edited, folded, spindled, mutilated,
eviscerated, contemplated, discombobulated, cogitated,
regurgitated, rebuilt, castigated, and reinvigorated over the
last decade, by a cast of hundreds if not thousands.
Repeatedly.</para>
<para>We wish to thank every one of the people responsible, and we
encourage you to <link
xlink:href="&url.articles.contributing;/article.html">join
them</link> in making this <acronym>FAQ</acronym> even
better.</para>
</chapter>
&bibliography;
</book>
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