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Glen Barber e05926f374 MF ISBN: 
Merged /projects/print2013/en_US.ISO8859-1:r40693-40726
   Merged /projects/ISBN_1-57176-407-0/en_US.ISO8859-1:r40727-41455,
	41457-41469,41472-41477,41479-41513,41515-41521,41523-41577,
	41579-41581,41583-42013

Notes:  This merge entirely excludes the en_US/books/handbook/ppp-and-slip/
changes.  They will need to be looked at a bit more closely.

Note to translators:  I am very, very sorry.  There was no *clean* way
to merge this as separate commits.  Trust me, I tried.
The revision logs for the ISBN branch should provide some insight to what
content has changed.  I am more than happy to help out here.  Sorry :(

Approved by:	doceng (implicit)
2013-06-23 22:37:08 +00:00

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<?xml version="1.0" encoding="iso-8859-1"?>
<!--
The FreeBSD Documentation Project
$FreeBSD$
-->
<chapter id="network-servers">
<chapterinfo>
<authorgroup>
<author>
<firstname>Murray</firstname>
<surname>Stokely</surname>
<contrib>Reorganized by </contrib>
</author>
</authorgroup>
<!-- 23 July 2004 -->
</chapterinfo>
<title>Network Servers</title>
<sect1 id="network-servers-synopsis">
<title>Synopsis</title>
<para>This chapter will cover some of the more frequently used
network services on &unix; systems. We will cover how to
install, configure, test, and maintain many different types of
network services. Example configuration files are included
throughout this chapter for you to benefit from.</para>
<para>After reading this chapter, you will know:</para>
<itemizedlist>
<listitem>
<para>How to manage the <application>inetd</application>
daemon.</para>
</listitem>
<listitem>
<para>How to set up a network file system.</para>
</listitem>
<listitem>
<para>How to set up a network information server for sharing
user accounts.</para>
</listitem>
<listitem>
<para>How to set &os; up to act as an <acronym>LDAP</acronym>
server or client</para>
</listitem>
<listitem>
<para>How to set &os; up to act as an <acronym>LDAP</acronym>
server or client</para>
</listitem>
<listitem>
<para>How to set up automatic network settings using
DHCP.</para>
</listitem>
<listitem>
<para>How to set up a domain name server.</para>
</listitem>
<listitem>
<para>How to set up the <application>Apache</application>
HTTP Server.</para>
</listitem>
<listitem>
<para>How to set up a File Transfer Protocol (FTP)
Server.</para>
</listitem>
<listitem>
<para>How to set up a file and print server for &windows;
clients using <application>Samba</application>.</para>
</listitem>
<listitem>
<para>How to synchronize the time and date, and set up a
time server, with the NTP protocol.</para>
</listitem>
<listitem>
<para>How to configure the standard logging daemon,
<command>syslogd</command>, to accept logs from remote
hosts.</para>
</listitem>
</itemizedlist>
<para>Before reading this chapter, you should:</para>
<itemizedlist>
<listitem>
<para>Understand the basics of the
<filename>/etc/rc</filename> scripts.</para>
</listitem>
<listitem>
<para>Be familiar with basic network terminology.</para>
</listitem>
<listitem>
<para>Know how to install additional third-party
software (<xref linkend="ports"/>).</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="network-inetd">
<sect1info>
<authorgroup>
<author>
<firstname>Chern</firstname>
<surname>Lee</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<contrib>Updated by </contrib>
<othername>The &os; Documentation Project</othername>
</author>
</authorgroup>
</sect1info>
<title>The <application>inetd</application>
<quote>Super-Server</quote></title>
<sect2 id="network-inetd-overview">
<title>Overview</title>
<para>The &man.inetd.8; daemon is sometimes referred to as the
<quote>Internet Super-Server</quote> because it manages
connections for many services. When a connection is
received by <application>inetd</application>, it determines
which program the connection is destined for, spawns the
particular process and delegates the socket to it (the program
is invoked with the service socket as its standard input,
output and error descriptors). Running
<application>inetd</application> for servers that are not
heavily used can reduce the overall system load, when compared
to running each daemon individually in stand-alone
mode.</para>
<para>Primarily, <application>inetd</application> is used to
spawn other daemons, but several trivial protocols are handled
directly, such as <application>chargen</application>,
<application>auth</application>, and
<application>daytime</application>.</para>
<para>This section will cover the basics in configuring
<application>inetd</application> through its command-line
options and its configuration file,
<filename>/etc/inetd.conf</filename>.</para>
</sect2>
<sect2 id="network-inetd-settings">
<title>Settings</title>
<para><application>inetd</application> is initialized through
the &man.rc.8; system. The
<literal>inetd_enable</literal> option is set to
<literal>NO</literal> by default, but may be turned on
by <application>sysinstall</application> during installation,
depending on the configuration chosen by the user.
Placing:</para>
<programlisting>inetd_enable="YES"</programlisting>
<para>or</para>
<programlisting>inetd_enable="NO"</programlisting>
<para>into
<filename>/etc/rc.conf</filename> will enable or disable
<application>inetd</application> starting at boot time.
The command:</para>
<screen>&prompt.root; <userinput>service inetd rcvar</userinput></screen>
<para>can be run to display the current effective setting.</para>
<para>Additionally, different command-line options can be passed
to <application>inetd</application> via the
<literal>inetd_flags</literal> option.</para>
</sect2>
<sect2 id="network-inetd-cmdline">
<title>Command-Line Options</title>
<para>Like most server daemons, <application>inetd</application>
has a number of options that it can be passed in order to
modify its behaviour. See the &man.inetd.8; manual page for
the full list of options.</para>
<para>Options can be passed to <application>inetd</application>
using the <literal>inetd_flags</literal> option in
<filename>/etc/rc.conf</filename>. By default,
<literal>inetd_flags</literal> is set to
<literal>-wW -C 60</literal>, which turns on TCP wrapping for
<application>inetd</application>'s services, and prevents any
single IP address from requesting any service more than 60
times in any given minute.</para>
<para>Although we mention rate-limiting options below, novice
users may be pleased to note that these parameters usually do
not need to be modified. These options may be useful if
an excessive amount of connections are being established.
A full list of options can be found in the
&man.inetd.8; manual.</para>
<variablelist>
<varlistentry>
<term>-c maximum</term>
<listitem>
<para>Specify the default maximum number of simultaneous
invocations of each service; the default is unlimited.
May be overridden on a per-service basis with the
<option>max-child</option> parameter.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-C rate</term>
<listitem>
<para>Specify the default maximum number of times a
service can be invoked from a single IP address in one
minute; the default is unlimited. May be overridden on
a per-service basis with the
<option>max-connections-per-ip-per-minute</option>
parameter.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-R rate</term>
<listitem>
<para>Specify the maximum number of times a service can be
invoked in one minute; the default is 256. A rate of 0
allows an unlimited number of invocations.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-s maximum</term>
<listitem>
<para>Specify the maximum number of times a service can be
invoked from a single IP address at any one time; the
default is unlimited. May be overridden on a
per-service basis with the
<option>max-child-per-ip</option> parameter.</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2 id="network-inetd-conf">
<!-- XXX This section isn't very clear, and could do with some lovin' -->
<title><filename>inetd.conf</filename></title>
<para>Configuration of <application>inetd</application> is
done via the file <filename>/etc/inetd.conf</filename>.</para>
<para>When a modification is made to
<filename>/etc/inetd.conf</filename>,
<application>inetd</application> can be forced to re-read its
configuration file by running the command:</para>
<example id="network-inetd-reread">
<title>Reloading the <application>inetd</application>
Configuration File</title>
<screen>&prompt.root; <userinput>service inetd reload</userinput></screen>
</example>
<para>Each line of the configuration file specifies an
individual daemon. Comments in the file are preceded by a
<quote>#</quote>. The format of each entry in
<filename>/etc/inetd.conf</filename> is as follows:</para>
<programlisting>service-name
socket-type
protocol
{wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]
user[:group][/login-class]
server-program
server-program-arguments</programlisting>
<para>An example entry for the &man.ftpd.8; daemon
using IPv4 might read:</para>
<programlisting>ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l</programlisting>
<variablelist>
<varlistentry>
<term>service-name</term>
<listitem>
<para>This is the service name of the particular daemon.
It must correspond to a service listed in
<filename>/etc/services</filename>. This determines
which port <application>inetd</application> must listen
to. If a new service is being created, it must be
placed in <filename>/etc/services</filename>
first.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>socket-type</term>
<listitem>
<para>Either <literal>stream</literal>,
<literal>dgram</literal>, <literal>raw</literal>, or
<literal>seqpacket</literal>. <literal>stream</literal>
must be used for connection-based, TCP daemons, while
<literal>dgram</literal> is used for daemons utilizing
the <acronym>UDP</acronym> transport protocol.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>protocol</term>
<listitem>
<para>One of the following:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>Protocol</entry>
<entry>Explanation</entry>
</row>
</thead>
<tbody>
<row>
<entry>tcp, tcp4</entry>
<entry>TCP IPv4</entry>
</row>
<row>
<entry>udp, udp4</entry>
<entry>UDP IPv4</entry>
</row>
<row>
<entry>tcp6</entry>
<entry>TCP IPv6</entry>
</row>
<row>
<entry>udp6</entry>
<entry>UDP IPv6</entry>
</row>
<row>
<entry>tcp46</entry>
<entry>Both TCP IPv4 and v6</entry>
</row>
<row>
<entry>udp46</entry>
<entry>Both UDP IPv4 and v6</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</listitem>
</varlistentry>
<varlistentry>
<term>{wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]</term>
<listitem>
<para><option>wait|nowait</option> indicates whether the
daemon invoked from <application>inetd</application> is
able to handle its own socket or not.
<option>dgram</option> socket types must use the
<option>wait</option> option, while stream socket
daemons, which are usually multi-threaded, should use
<option>nowait</option>. <option>wait</option> usually
hands off multiple sockets to a single daemon, while
<option>nowait</option> spawns a child daemon for each
new socket.</para>
<para>The maximum number of child daemons
<application>inetd</application> may spawn can be set
using the <option>max-child</option> option. If a limit
of ten instances of a particular daemon is needed, a
<literal>/10</literal> would be placed after
<option>nowait</option>. Specifying
<literal>/0</literal> allows an unlimited number of
children</para>
<para>In addition to <option>max-child</option>, two other
options which limit the maximum connections from a
single place to a particular daemon can be enabled.
<option>max-connections-per-ip-per-minute</option>
limits the number of connections from any particular IP
address per minutes, e.g., a value of ten would limit
any particular IP address connecting to a particular
service to ten attempts per minute.
<option>max-child-per-ip</option> limits the number of
children that can be started on behalf on any single IP
address at any moment. These options are useful to
prevent intentional or unintentional excessive resource
consumption and Denial of Service (DoS) attacks to a
machine.</para>
<para>In this field, either of <option>wait</option> or
<option>nowait</option> is mandatory.
<option>max-child</option>,
<option>max-connections-per-ip-per-minute</option> and
<option>max-child-per-ip</option> are
optional.</para>
<para>A stream-type multi-threaded daemon without any
<option>max-child</option>,
<option>max-connections-per-ip-per-minute</option> or
<option>max-child-per-ip</option> limits
would simply be: <literal>nowait</literal>.</para>
<para>The same daemon with a maximum limit of ten daemons
would read: <literal>nowait/10</literal>.</para>
<para>The same setup with a limit of twenty
connections per IP address per minute and a maximum
total limit of ten child daemons would read:
<literal>nowait/10/20</literal>.</para>
<para>These options are utilized by the default
settings of the &man.fingerd.8; daemon,
as seen here:</para>
<programlisting>finger stream tcp nowait/3/10 nobody /usr/libexec/fingerd fingerd -s</programlisting>
<para>Finally, an example of this field with a maximum of
100 children in total, with a maximum of 5 for any one
IP address would read:
<literal>nowait/100/0/5</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>user</term>
<listitem>
<para>This is the username that the particular daemon
should run as. Most commonly, daemons run as the
<username>root</username> user. For security purposes,
it is common to find some servers running as the
<username>daemon</username> user, or the least
privileged <username>nobody</username> user.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>server-program</term>
<listitem>
<para>The full path of the daemon to be executed when a
connection is received. If the daemon is a service
provided by <application>inetd</application> internally,
then <option>internal</option> should be
used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>server-program-arguments</term>
<listitem>
<para>This works in conjunction with
<option>server-program</option> by specifying the
arguments, starting with <literal>argv[0]</literal>,
passed to the daemon on invocation. If
<command>mydaemon -d</command> is the command line,
<literal>mydaemon -d</literal> would be the value of
<option>server-program-arguments</option>. Again, if
the daemon is an internal service, use
<option>internal</option> here.</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2 id="network-inetd-security">
<title>Security</title>
<para>Depending on the choices made at install time, many
of <application>inetd</application>'s services may be enabled
by default. If there is no apparent need for a particular
daemon, consider disabling it. Place a <quote>#</quote> in
front of the daemon in question in
<filename>/etc/inetd.conf</filename>, and then <link
linkend="network-inetd-reread">reload the
inetd configuration</link>. Some daemons, such as
<application>fingerd</application>, may not be desired at all
because they provide
information that may be useful to an attacker.</para>
<para>Some daemons are not security-conscious and have long, or
non-existent, timeouts for connection attempts. This allows
an attacker to slowly send connections to a particular daemon,
thus saturating available resources. It may be a good idea to
place <option>max-connections-per-ip-per-minute</option>,
<option>max-child</option> or
<option>max-child-per-ip</option> limitations on certain
daemons if there are too many connections.</para>
<para>By default, TCP wrapping is turned on. Consult the
&man.hosts.access.5; manual page for more information on
placing TCP restrictions on various
<application>inetd</application> invoked daemons.</para>
</sect2>
<sect2 id="network-inetd-misc">
<title>Miscellaneous</title>
<para><application>daytime</application>,
<application>time</application>,
<application>echo</application>,
<application>discard</application>,
<application>chargen</application>, and
<application>auth</application> are all internally provided
services of <application>inetd</application>.</para>
<para>The <application>auth</application> service provides
identity network services, and is
configurable to a certain degree, whilst the others are simply
on or off.</para>
<para>Consult the &man.inetd.8; manual page for more in-depth
information.</para>
</sect2>
</sect1>
<sect1 id="network-nfs">
<sect1info>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
<contrib>Reorganized and enhanced by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<firstname>Bill</firstname>
<surname>Swingle</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</sect1info>
<title>Network File System (NFS)</title>
<indexterm><primary>NFS</primary></indexterm>
<para>Among the many different file systems that FreeBSD supports
is the Network File System, also known as <acronym role="Network
File System">NFS</acronym>. <acronym role="Network File
System">NFS</acronym> allows a system to share directories and
files with others over a network. By using <acronym
role="Network File System">NFS</acronym>, users and programs can
access files on remote systems almost as if they were local
files.</para>
<para>Some of the most notable benefits that
<acronym>NFS</acronym> can provide are:</para>
<itemizedlist>
<listitem>
<para>Local workstations use less disk space because commonly
used data can be stored on a single machine and still remain
accessible to others over the network.</para>
</listitem>
<listitem>
<para>There is no need for users to have separate home
directories on every network machine. Home directories
could be set up on the <acronym>NFS</acronym> server and
made available throughout the network.</para>
</listitem>
<listitem>
<para>Storage devices such as floppy disks, CDROM drives, and
&iomegazip; drives can be used by other machines on the
network. This may reduce the number of removable media
drives throughout the network.</para>
</listitem>
</itemizedlist>
<sect2>
<title>How <acronym>NFS</acronym> Works</title>
<para><acronym>NFS</acronym> consists of at least two main
parts: a server and one or more clients. The client remotely
accesses the data that is stored on the server machine. In
order for this to function properly a few processes have to be
configured and running.</para>
<para>The server has to be running the following daemons:</para>
<indexterm>
<primary>NFS</primary>
<secondary>server</secondary>
</indexterm>
<indexterm>
<primary>file server</primary>
<secondary>UNIX clients</secondary>
</indexterm>
<indexterm>
<primary><application>rpcbind</application></primary>
</indexterm>
<indexterm>
<primary><application>mountd</application></primary>
</indexterm>
<indexterm>
<primary><application>nfsd</application></primary>
</indexterm>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<colspec colwidth="1*"/>
<colspec colwidth="3*"/>
<thead>
<row>
<entry>Daemon</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><application>nfsd</application></entry>
<entry>The <acronym>NFS</acronym> daemon which services
requests from the <acronym>NFS</acronym>
clients.</entry>
</row>
<row>
<entry><application>mountd</application></entry>
<entry>The <acronym>NFS</acronym> mount daemon which
carries out the requests that &man.nfsd.8; passes on
to it.</entry>
</row>
<row>
<entry><application>rpcbind</application></entry>
<entry> This daemon allows
<acronym>NFS</acronym> clients to discover which port
the <acronym>NFS</acronym> server is using.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>The client can also run a daemon, known as
<application>nfsiod</application>. The
<application>nfsiod</application> daemon services the requests
from the <acronym>NFS</acronym> server. This is optional, and
improves performance, but is not required for normal and
correct operation. See the &man.nfsiod.8; manual page for
more information.</para>
</sect2>
<sect2 id="network-configuring-nfs">
<title>Configuring <acronym>NFS</acronym></title>
<indexterm>
<primary>NFS</primary>
<secondary>configuration</secondary>
</indexterm>
<para><acronym>NFS</acronym> configuration is a relatively
straightforward process. The processes that need to be
running can all start at boot time with a few modifications
to <filename>/etc/rc.conf</filename>.</para>
<para>On the <acronym>NFS</acronym> server, make sure that the
following options are configured in the
<filename>/etc/rc.conf</filename> file:</para>
<programlisting>rpcbind_enable="YES"
nfs_server_enable="YES"
mountd_flags="-r"</programlisting>
<para><application>mountd</application> runs automatically
whenever the <acronym>NFS</acronym> server is enabled.</para>
<para>On the client, make sure this option is present in
<filename>/etc/rc.conf</filename>:</para>
<programlisting>nfs_client_enable="YES"</programlisting>
<para>The <filename>/etc/exports</filename> file specifies which
file systems <acronym>NFS</acronym> should export (sometimes
referred to as <quote>share</quote>). Each line in
<filename>/etc/exports</filename> specifies a file system to
be exported and which machines have access to that file
system. Along with what machines have access to that file
system, access options may also be specified. There are many
such options that can be used in this file but only a few will
be mentioned here. Other options are discussed in
the &man.exports.5; manual page.</para>
<para>Here are a few example <filename>/etc/exports</filename>
entries:</para>
<indexterm>
<primary>NFS</primary>
<secondary>export examples</secondary>
</indexterm>
<para>The following examples give an idea of how to export
file systems, although the settings may be different depending
on the environment and network configuration. For instance,
to export the <filename>/cdrom</filename> directory to three
example machines that have the same domain name as the server
(hence the lack of a domain name for each) or have entries in
the <filename>/etc/hosts</filename> file. The
<option>-ro</option> flag makes the exported file system
read-only. With this flag, the remote system will not be able
to write any changes to the exported file system.</para>
<programlisting>/cdrom -ro host1 host2 host3</programlisting>
<para>The following line exports <filename>/home</filename> to
three hosts by IP address. This is a useful setup on
a private network without a <acronym>DNS</acronym> server
configured. Optionally the <filename>/etc/hosts</filename>
file could be configured for internal hostnames; please review
&man.hosts.5; for more information. The
<option>-alldirs</option> flag allows the subdirectories to be
mount points. In other words, it will not mount the
subdirectories but permit the client to mount only the
directories that are required or needed.</para>
<programlisting>/home -alldirs 10.0.0.2 10.0.0.3 10.0.0.4</programlisting>
<para>The following line exports <filename>/a</filename> so that
two clients from different domains may access the file system.
The <option>-maproot=root</option> flag allows the
<username>root</username> user on the remote system to write
data on the exported file system as <username>root</username>.
If the <literal>-maproot=root</literal> flag is not specified,
then even if a user has <username>root</username> access on
the remote system, he will not be able to modify files on
the exported file system.</para>
<programlisting>/a -maproot=root host.example.com box.example.org</programlisting>
<para>In order for a client to access an exported file system,
the client must have permission to do so. Make sure the
client is listed in <filename>/etc/exports</filename>.</para>
<para>In <filename>/etc/exports</filename>, each line represents
the export information for one file system to one host. A
remote host can only be specified once per file system, and
may only have one default entry. For example, assume that
<filename>/usr</filename> is a single file system. The
following <filename>/etc/exports</filename> would be
invalid:</para>
<programlisting># Invalid when /usr is one file system
/usr/src client
/usr/ports client</programlisting>
<para>One file system, <filename>/usr</filename>, has two lines
specifying exports to the same host, <hostid>client</hostid>.
The correct format for this situation is:</para>
<programlisting>/usr/src /usr/ports client</programlisting>
<para>The properties of one file system exported to a given host
must all occur on one line. Lines without a client specified
are treated as a single host. This limits how file systems
may be exported; however, for most environments, this is not
an issue.</para>
<para>The following is an example of a valid export list, where
<filename>/usr</filename> and <filename>/exports</filename>
are local file systems:</para>
<programlisting># Export src and ports to client01 and client02, but only
# client01 has root privileges on it
/usr/src /usr/ports -maproot=root client01
/usr/src /usr/ports client02
# The client machines have root and can mount anywhere
# on /exports. Anyone in the world can mount /exports/obj read-only
/exports -alldirs -maproot=root client01 client02
/exports/obj -ro</programlisting>
<para>The <application>mountd</application> daemon must be
forced to recheck the <filename>/etc/exports</filename> file
whenever it has been modified, so the changes can take effect.
This can be accomplished either by sending a HUP signal to the
running daemon:</para>
<screen>&prompt.root; <userinput>kill -HUP `cat /var/run/mountd.pid`</userinput></screen>
<para>or by invoking the <command>mountd</command> &man.rc.8;
script with the appropriate parameter:</para>
<screen>&prompt.root; <userinput>service mountd onereload</userinput></screen>
<para>Please refer to <xref linkend="configtuning-rcd"/> for
more information about using rc scripts.</para>
<para>Alternatively, a reboot will make FreeBSD set everything
up properly. A reboot is not necessary though.
Executing the following commands as <username>root</username>
should start everything up.</para>
<para>On the <acronym>NFS</acronym> server:</para>
<screen>&prompt.root; <userinput>rpcbind</userinput>
&prompt.root; <userinput>nfsd -u -t -n 4</userinput>
&prompt.root; <userinput>mountd -r</userinput></screen>
<para>On the <acronym>NFS</acronym> client:</para>
<screen>&prompt.root; <userinput>nfsiod -n 4</userinput></screen>
<para>Now everything should be ready to actually mount a remote
file system. In these examples the server's name will be
<hostid>server</hostid> and the client's name will be
<hostid>client</hostid>. For testing or to temporarily
mount a remote file system execute a command like this as
<username>root</username> on the client:</para>
<indexterm>
<primary>NFS</primary>
<secondary>mounting</secondary>
</indexterm>
<screen>&prompt.root; <userinput>mount server:/home /mnt</userinput></screen>
<para>This will mount the <filename>/home</filename> directory
on the server at <filename>/mnt</filename> on the client. If
everything is set up correctly, the server's files should be
visible and available in the <filename>/mnt</filename>
directory.</para>
<para>To permanently mount a remote file system
each time the computer boots, add the file system to the
<filename>/etc/fstab</filename> file. Here is an
example:</para>
<programlisting>server:/home /mnt nfs rw 0 0</programlisting>
<para>The &man.fstab.5; manual page lists all the available
options.</para>
</sect2>
<sect2>
<title>Locking</title>
<para>Some applications (e.g., <application>mutt</application>)
require file locking to operate correctly. In the case of
<acronym>NFS</acronym>, <application>rpc.lockd</application>
can be used for file locking. To enable it, add the following
to the <filename>/etc/rc.conf</filename> file on both client
and server (it is assumed that the <acronym>NFS</acronym>
client and server are configured already):</para>
<programlisting>rpc_lockd_enable="YES"
rpc_statd_enable="YES"</programlisting>
<para>Start the application by using:</para>
<screen>&prompt.root; <userinput>service lockd start</userinput>
&prompt.root; <userinput>service statd start</userinput></screen>
<para>If real locking between the <acronym>NFS</acronym> clients
and <acronym>NFS</acronym> server is not required, it is
possible to let the <acronym>NFS</acronym> client do locking
locally by passing <option>-L</option> to &man.mount.nfs.8;.
Refer to the &man.mount.nfs.8; manual page for further
details.</para>
</sect2>
<sect2>
<title>Practical Uses</title>
<para><acronym>NFS</acronym> has many practical uses. Some of
the more common ones are listed below:</para>
<indexterm>
<primary>NFS</primary>
<secondary>uses</secondary>
</indexterm>
<itemizedlist>
<listitem>
<para>Set several machines to share a CDROM or other media
among them. This is cheaper and often a more convenient
method to install software on multiple machines.</para>
</listitem>
<listitem>
<para>On large networks, it might be more convenient to
configure a central <acronym>NFS</acronym> server in which
to store all the user home directories. These home
directories can then be exported to the network so that
users would always have the same home directory,
regardless of which workstation they log in to.</para>
</listitem>
<listitem>
<para>Several machines could have a common
<filename>/usr/ports/distfiles</filename> directory. This
allows for quick access to the source files without
downloading them on each machine.</para>
</listitem>
</itemizedlist>
</sect2>
<sect2 id="network-amd">
<sect2info>
<authorgroup>
<author>
<firstname>Wylie</firstname>
<surname>Stilwell</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<firstname>Chern</firstname>
<surname>Lee</surname>
<contrib>Rewritten by </contrib>
</author>
</authorgroup>
</sect2info>
<title>Automatic Mounts with
<application>amd</application></title>
<indexterm><primary>amd</primary></indexterm>
<indexterm>
<primary>automatic mounter daemon</primary>
</indexterm>
<para>&man.amd.8; (the automatic mounter daemon)
automatically mounts a
remote file system whenever a file or directory within that
file system is accessed. Filesystems that are inactive for a
period of time will also be automatically unmounted by
<application>amd</application>. Using
<application>amd</application> provides a simple alternative
to permanent mounts, as permanent mounts are usually listed in
<filename>/etc/fstab</filename>.</para>
<para><application>amd</application> operates by attaching
itself as an NFS server to the <filename>/host</filename> and
<filename>/net</filename> directories. When a file is
accessed within one of these directories,
<application>amd</application> looks up the corresponding
remote mount and automatically mounts it.
<filename>/net</filename> is used to mount an exported file
system from an IP address, while <filename>/host</filename>
is used to mount an export from a remote hostname.</para>
<para>An access to a file within
<filename>/host/foobar/usr</filename> would tell
<application>amd</application> to attempt to mount the
<filename>/usr</filename> export on the host
<hostid>foobar</hostid>.</para>
<example>
<title>Mounting an Export with
<application>amd</application></title>
<para>The <command>showmount</command> command shows the
available mounts on a remote host. For example, to
view the mounts of a host named
<hostid>foobar</hostid>:</para>
<screen>&prompt.user; <userinput>showmount -e foobar</userinput>
Exports list on foobar:
/usr 10.10.10.0
/a 10.10.10.0
&prompt.user; <userinput>cd /host/foobar/usr</userinput></screen>
</example>
<para>As seen in the example, the <command>showmount</command>
shows <filename>/usr</filename> as an export. When changing
directories to <filename>/host/foobar/usr</filename>,
<application>amd</application> attempts to resolve the
hostname <hostid>foobar</hostid> and automatically mount the
desired export.</para>
<para><application>amd</application> can be started by the
startup scripts by placing the following lines in
<filename>/etc/rc.conf</filename>:</para>
<programlisting>amd_enable="YES"</programlisting>
<para>Additionally, custom flags can be passed to
<application>amd</application> from the
<varname>amd_flags</varname> option. By default,
<varname>amd_flags</varname> is set to:</para>
<programlisting>amd_flags="-a /.amd_mnt -l syslog /host /etc/amd.map /net /etc/amd.map"</programlisting>
<para>The <filename>/etc/amd.map</filename> file defines the
default options that exports are mounted with. The
<filename>/etc/amd.conf</filename> file defines some of the
more advanced features of
<application>amd</application>.</para>
<para>Consult the &man.amd.8; and &man.amd.conf.5; manual pages
for more information.</para>
</sect2>
<sect2 id="network-nfs-integration">
<sect2info>
<authorgroup>
<author>
<firstname>John</firstname>
<surname>Lind</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect2info>
<title>Problems Integrating with Other Systems</title>
<para>Certain Ethernet adapters for ISA PC systems have
limitations which can lead to serious network problems,
particularly with NFS. This difficulty is not specific to
FreeBSD, but FreeBSD systems are affected by it.</para>
<para>The problem nearly always occurs when (FreeBSD) PC systems
are networked with high-performance workstations, such as
those made by Silicon Graphics, Inc., and Sun Microsystems,
Inc. The NFS mount will work fine, and some operations may
succeed, but suddenly the server will seem to become
unresponsive to the client, even though requests to and from
other systems continue to be processed. This happens to the
client system, whether the client is the FreeBSD system or the
workstation. On many systems, there is no way to shut down
the client gracefully once this problem has manifested itself.
The only solution is often to reset the client, because the
NFS situation cannot be resolved.</para>
<para>Though the <quote>correct</quote> solution is to get a
higher performance and capacity Ethernet adapter for the
FreeBSD system, there is a simple workaround that will allow
satisfactory operation. If the FreeBSD system is the
<emphasis>server</emphasis>, include the option
<option>-w=1024</option> on the mount from the client. If the
FreeBSD system is the <emphasis>client</emphasis>, then mount
the NFS file system with the option <option>-r=1024</option>.
These options may be specified using the fourth field of the
<filename>fstab</filename> entry on the client for automatic
mounts, or by using the <option>-o</option> parameter of the
&man.mount.8; command for manual mounts.</para>
<para>It should be noted that there is a different problem,
sometimes mistaken for this one, when the NFS servers and
clients are on different networks. If that is the case, make
<emphasis>certain</emphasis> that the routers are routing the
necessary <acronym>UDP</acronym> information.</para>
<para>In the following examples, <hostid>fastws</hostid> is the
host (interface) name of a high-performance workstation, and
<hostid>freebox</hostid> is the host (interface) name of a
FreeBSD system with a lower-performance Ethernet adapter.
Also, <filename>/sharedfs</filename> will be the exported NFS
file system (see &man.exports.5;), and
<filename>/project</filename> will be the mount point on the
client for the exported file system. In all cases, note that
additional options, such as <option>hard</option> or
<option>soft</option> and <option>bg</option> may be desirable
in the application.</para>
<para>Examples for the FreeBSD system (<hostid>freebox</hostid>)
as the client in <filename>/etc/fstab</filename> on
<hostid>freebox</hostid>:</para>
<programlisting>fastws:/sharedfs /project nfs rw,-r=1024 0 0</programlisting>
<para>As a manual mount command on
<hostid>freebox</hostid>:</para>
<screen>&prompt.root; <userinput>mount -t nfs -o -r=1024 fastws:/sharedfs /project</userinput></screen>
<para>Examples for the FreeBSD system as the server in
<filename>/etc/fstab</filename> on
<hostid>fastws</hostid>:</para>
<programlisting>freebox:/sharedfs /project nfs rw,-w=1024 0 0</programlisting>
<para>As a manual mount command on
<hostid>fastws</hostid>:</para>
<screen>&prompt.root; <userinput>mount -t nfs -o -w=1024 freebox:/sharedfs /project</userinput></screen>
<para>Nearly any 16-bit Ethernet adapter will allow operation
without the above restrictions on the read or write
size.</para>
<para>For anyone who cares, here is what happens when the
failure occurs, which also explains why it is unrecoverable.
NFS typically works with a <quote>block</quote> size of
8&nbsp;K (though it may do fragments of smaller sizes). Since
the maximum Ethernet packet is around 1500&nbsp;bytes, the NFS
<quote>block</quote> gets split into multiple Ethernet
packets, even though it is still a single unit to the
upper-level code, and must be received, assembled, and
<emphasis>acknowledged</emphasis> as a unit. The
high-performance workstations can pump out the packets which
comprise the NFS unit one right after the other, just as close
together as the standard allows. On the smaller, lower
capacity cards, the later packets overrun the earlier packets
of the same unit before they can be transferred to the host
and the unit as a whole cannot be reconstructed or
acknowledged. As a result, the workstation will time out and
try again, but it will try again with the entire 8&nbsp;K
unit, and the process will be repeated, ad infinitum.</para>
<para>By keeping the unit size below the Ethernet packet size
limitation, we ensure that any complete Ethernet packet
received can be acknowledged individually, avoiding the
deadlock situation.</para>
<para>Overruns may still occur when a high-performance
workstations is slamming data out to a PC system, but with the
better cards, such overruns are not guaranteed on NFS
<quote>units</quote>. When an overrun occurs, the units
affected will be retransmitted, and there will be a fair
chance that they will be received, assembled, and
acknowledged.</para>
</sect2>
</sect1>
<sect1 id="network-nis">
<sect1info>
<authorgroup>
<author>
<firstname>Bill</firstname>
<surname>Swingle</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<firstname>Eric</firstname>
<surname>Ogren</surname>
<contrib>Enhanced by </contrib>
</author>
<author>
<firstname>Udo</firstname>
<surname>Erdelhoff</surname>
</author>
</authorgroup>
</sect1info>
<title>Network Information System (NIS/YP)</title>
<sect2>
<title>What Is It?</title>
<indexterm><primary>NIS</primary></indexterm>
<indexterm><primary>Solaris</primary></indexterm>
<indexterm><primary>HP-UX</primary></indexterm>
<indexterm><primary>AIX</primary></indexterm>
<indexterm><primary>Linux</primary></indexterm>
<indexterm><primary>NetBSD</primary></indexterm>
<indexterm><primary>OpenBSD</primary></indexterm>
<para><acronym role="Network Information System">NIS</acronym>,
which stands for Network Information Services, was developed
by Sun Microsystems to centralize administration of &unix;
(originally &sunos;) systems. It has now essentially become
an industry standard; all major &unix; like systems
(&solaris;, HP-UX, &aix;, Linux, NetBSD, OpenBSD, FreeBSD,
etc) support <acronym
role="Network Information System">NIS</acronym>.</para>
<indexterm>
<primary>yellow pages</primary>
<see>NIS</see>
</indexterm>
<para><acronym role="Network Information System">NIS</acronym>
was formerly known as Yellow Pages, but because of trademark
issues, Sun changed the name. The old term (and yp) is still
often seen and used.</para>
<indexterm>
<primary>NIS</primary>
<secondary>domains</secondary>
</indexterm>
<para>It is a RPC-based client/server system that allows a group
of machines within an NIS domain to share a common set of
configuration files. This permits a system administrator to
set up NIS client systems with only minimal configuration data
and add, remove or modify configuration data from a single
location.</para>
<indexterm><primary>Windows NT</primary></indexterm>
<para>It is similar to the &windowsnt; domain system; although
the internal implementation of the two are not at all similar,
the basic functionality can be compared.</para>
</sect2>
<sect2>
<title><acronym>NIS</acronym>Terms and Processes</title>
<para>There are several terms and important user
processes that will be explained while attempting to
implement NIS on FreeBSD, regardless if the system is a
NIS server or a NIS client:</para>
<indexterm>
<primary><application>rpcbind</application></primary>
</indexterm>
<indexterm>
<primary><application>portmap</application></primary>
</indexterm>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<colspec colwidth="1*"/>
<colspec colwidth="3*"/>
<thead>
<row>
<entry>Term</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>NIS domainname</entry>
<entry>An NIS master server and all of its clients
(including its slave servers) have a NIS domainname.
Similar to an &windowsnt; domain name, the NIS
domainname does not have anything to do with
<acronym>DNS</acronym>.</entry>
</row>
<row>
<entry><application>rpcbind</application></entry>
<entry>Must be running in order to enable
<acronym>RPC</acronym> (Remote Procedure Call, a
network protocol used by NIS). If
<application>rpcbind</application> is not running, it
will be impossible to run an NIS server, or to act as
an NIS client.</entry>
</row>
<row>
<entry><application>ypbind</application></entry>
<entry><quote>Binds</quote> an NIS client to its NIS
server. It will take the NIS domainname from the
system, and using <acronym>RPC</acronym>, connect to
the server. <application>ypbind</application> is the
core of client-server communication in an NIS
environment; if <application>ypbind</application> dies
on a client machine, it will not be able to access the
NIS server.</entry>
</row>
<row>
<entry><application>ypserv</application></entry>
<entry>Should only be running on NIS servers; this is
the NIS server process itself. If &man.ypserv.8;
dies, then the server will no longer be able to
respond to NIS requests (hopefully, there is a slave
server to take over for it). There are some
implementations of NIS (but not the FreeBSD one), that
do not try to reconnect to another server if the
server it used before dies. Often, the only thing
that helps in this case is to restart the server
process (or even the whole server) or the
<application>ypbind</application> process on the
client.</entry>
</row>
<row>
<entry><application>rpc.yppasswdd</application></entry>
<entry>Another process that should only be running on
NIS master servers; this is a daemon that will allow
NIS clients to change their NIS passwords. If this
daemon is not running, users will have to login to the
NIS master server and change their passwords
there.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<!-- XXX Missing: rpc.ypxfrd (not important, though) May only run
on the master -->
</sect2>
<sect2>
<title>How Does It Work?</title>
<para>There are three types of hosts in an NIS environment:
master servers, slave servers, and clients. Servers act as a
central repository for host configuration information. Master
servers hold the authoritative copy of this information, while
slave servers mirror this information for redundancy. Clients
rely on the servers to provide this information to
them.</para>
<para>Information in many files can be shared in this manner.
The <filename>master.passwd</filename>,
<filename>group</filename>, and <filename>hosts</filename>
files are commonly shared via NIS. Whenever a process on a
client needs information that would normally be found in these
files locally, it makes a query to the NIS server that it is
bound to instead.</para>
<sect3>
<title>Machine Types</title>
<itemizedlist>
<indexterm>
<primary>NIS</primary>
<secondary>master server</secondary>
</indexterm>
<listitem>
<para>A <emphasis>NIS master server</emphasis>. This
server, analogous to a &windowsnt; primary domain
controller, maintains the files used by all of the NIS
clients. The <filename>passwd</filename>,
<filename>group</filename>, and other various files used
by the NIS clients live on the master server.</para>
<note><para>It is possible for one machine to be an NIS
master server for more than one NIS domain. However,
this will not be covered in this introduction, which
assumes a relatively small-scale NIS
environment.</para></note>
</listitem>
<listitem>
<indexterm>
<primary>NIS</primary>
<secondary>slave server</secondary>
</indexterm>
<para><emphasis>NIS slave servers</emphasis>. Similar to
the &windowsnt; backup domain controllers, NIS slave
servers maintain copies of the NIS master's data files.
NIS slave servers provide the redundancy, which is
needed in important environments. They also help to
balance the load of the master server: NIS Clients
always attach to the NIS server whose response they get
first, and this includes slave-server-replies.</para>
</listitem>
<listitem>
<indexterm>
<primary>NIS</primary>
<secondary>client</secondary>
</indexterm>
<para><emphasis>NIS clients</emphasis>. NIS clients, like
most &windowsnt; workstations, authenticate against the
NIS server (or the &windowsnt; domain controller in the
&windowsnt; workstations case) to log on.</para>
</listitem>
</itemizedlist>
</sect3>
</sect2>
<sect2>
<title>Using NIS/YP</title>
<para>This section will deal with setting up a sample NIS
environment.</para>
<sect3>
<title>Planning</title>
<para>Let us assume that an administrator of a small
university lab, which consists of 15 FreeBSD
machines, currently has no centralized point of
administration. Each machine has its own
<filename>/etc/passwd</filename> and
<filename>/etc/master.passwd</filename>. These files are
kept in sync with each other only through manual
intervention; currently, a user is added to the lab, the
process must be ran on all 15 machines.
The lab would clearly benefit from the addition of two
<acronym>NIS</acronym> servers.</para>
<para>Therefore, the configuration of the lab now looks
something like:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="3">
<thead>
<row>
<entry>Machine name</entry>
<entry>IP address</entry>
<entry>Machine role</entry>
</row>
</thead>
<tbody>
<row>
<entry><hostid>ellington</hostid></entry>
<entry><hostid role="ipaddr">10.0.0.2</hostid></entry>
<entry>NIS master</entry>
</row>
<row>
<entry><hostid>coltrane</hostid></entry>
<entry><hostid role="ipaddr">10.0.0.3</hostid></entry>
<entry>NIS slave</entry>
</row>
<row>
<entry><hostid>basie</hostid></entry>
<entry><hostid role="ipaddr">10.0.0.4</hostid></entry>
<entry>Faculty workstation</entry>
</row>
<row>
<entry><hostid>bird</hostid></entry>
<entry><hostid role="ipaddr">10.0.0.5</hostid></entry>
<entry>Client machine</entry>
</row>
<row>
<entry><hostid>cli[1-11]</hostid></entry>
<entry>
<hostid role="ipaddr">10.0.0.[6-17]</hostid></entry>
<entry>Other client machines</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>If this is the first time a <acronym>NIS</acronym> scheme
is being developed, it should be thoroughly planned ahead of
time. Regardless of network size, several decisions need to
be made as part of the planning process.</para>
<sect4>
<title>Choosing a NIS Domain Name</title>
<indexterm>
<primary>NIS</primary>
<secondary>domainname</secondary>
</indexterm>
<para>This might not be the normal <quote>domainname</quote>
for the network. It is more accurately called the
<quote>NIS domainname</quote>. When a client broadcasts
its requests for info, it includes the name of the NIS
domain that it is part of. This is how multiple servers
on one network can tell which server should answer which
request. Think of the NIS domainname as the name for a
group of hosts that are related in some way.</para>
<para>Some organizations choose to use their Internet
domainname for their NIS domainname. This is not
recommended as it can cause confusion when trying to debug
network problems. The NIS domainname should be unique
within the network and it is helpful if it describes the
group of machines it represents. For example, the Art
department at Acme Inc. might be in the
<quote>acme-art</quote> NIS domain. For this example,
assume the chosen name will be
<literal>test-domain</literal>.</para>
<indexterm><primary>SunOS</primary></indexterm>
<para>However, some operating systems (notably &sunos;) use
their NIS domain name as their Internet domain name. If
one or more machines on the network have this
restriction, it <emphasis>must</emphasis> be used as the
Internet domain name for the NIS domain name.</para>
</sect4>
<sect4>
<title>Physical Server Requirements</title>
<para>There are several things to keep in mind when choosing
a machine to use as a NIS server. One of the unfortunate
things about NIS is the level of dependency the clients
have on the server. If a client cannot contact the server
for its NIS domain, very often the machine becomes
unusable. The lack of user and group information causes
most systems to temporarily freeze up. With this in mind
be sure to choose a machine that will not be
prone to being rebooted frequently, or one that might be
used for development. The NIS server should ideally be a
stand alone machine whose sole purpose in life is to be an
NIS server. If the network is not very
heavily used, it is acceptable to put the NIS server on a
machine running other services, however; if
the NIS server becomes unavailable, it will adversely affect
<emphasis>all</emphasis> NIS clients.</para>
</sect4>
</sect3>
<sect3>
<title>NIS Servers</title>
<para> The canonical copies of all NIS information are stored
on a single machine called the NIS master server. The
databases used to store the information are called NIS maps.
In FreeBSD, these maps are stored in
<filename>/var/yp/[domainname]</filename> where
<filename>[domainname]</filename> is the name of the NIS
domain being served. A single NIS server can support
several domains at once, therefore it is possible to have
several such directories, one for each supported domain.
Each domain will have its own independent set of
maps.</para>
<para>NIS master and slave servers handle all NIS requests
with the <command>ypserv</command> daemon.
<command>ypserv</command> is responsible for receiving
incoming requests from NIS clients, translating the
requested domain and map name to a path to the corresponding
database file and transmitting data from the database back
to the client.</para>
<sect4>
<title>Setting Up a NIS Master Server</title>
<indexterm>
<primary>NIS</primary>
<secondary>server configuration</secondary>
</indexterm>
<para>Setting up a master NIS server can be relatively
straight forward, depending on environmental needs. &os;
comes with support for NIS out-of-the-box. It only needs to
be enabled by adding the following lines to
<filename>/etc/rc.conf</filename>:</para>
<procedure>
<step>
<para><programlisting>nisdomainname="test-domain"</programlisting>
This line will set the NIS domainname to
<literal>test-domain</literal>
upon network setup (e.g., after reboot).</para>
</step>
<step>
<para><programlisting>nis_server_enable="YES"</programlisting>
This will tell FreeBSD to start up the NIS server
processes when the networking is next brought
up.</para>
</step>
<step>
<para><programlisting>nis_yppasswdd_enable="YES"</programlisting>
This will enable the <command>rpc.yppasswdd</command>
daemon which, as mentioned above, will allow users to
change their NIS password from a client
machine.</para>
</step>
</procedure>
<note>
<para>Depending on the NIS setup, additional entries may
be required. See the <link
linkend="network-nis-server-is-client">section about
NIS servers that are also NIS clients</link>, below, for
details.</para>
</note>
<para>After setting up the above entries, run the command
<command>/etc/netstart</command> as superuser. It will
set up everything, using the values defined in
<filename>/etc/rc.conf</filename>. As a last step, before
initializing the NIS maps, start the
<application>ypserv</application> daemon manually:</para>
<screen>&prompt.root; <userinput>service ypserv start</userinput></screen>
</sect4>
<sect4>
<title>Initializing the NIS Maps</title>
<indexterm>
<primary>NIS</primary>
<secondary>maps</secondary>
</indexterm>
<para>The <emphasis>NIS maps</emphasis> are database files,
that are kept in the <filename>/var/yp</filename>
directory. They are generated from configuration files in
the <filename>/etc</filename> directory of the NIS master,
with one exception: <filename>/etc/master.passwd</filename>.
This is for
a good reason, never propagate passwords for
<username>root</username> and other administrative
accounts to all the servers in the NIS domain. Therefore,
before the the NIS maps are initialized, configure the primary
password files:</para>
<screen>&prompt.root; <userinput>cp /etc/master.passwd /var/yp/master.passwd</userinput>
&prompt.root; <userinput>cd /var/yp</userinput>
&prompt.root; <userinput>vi master.passwd</userinput></screen>
<para>It is advisable to remove all entries regarding system
accounts (<username>bin</username>,
<username>tty</username>, <username>kmem</username>,
<username>games</username>, etc), as well as any accounts
that do not need to be propagated to the NIS clients
(for example <username>root</username> and any other UID 0
(superuser) accounts).</para>
<note><para>Ensure the
<filename>/var/yp/master.passwd</filename> is neither
group or world readable (mode 600)! Use the
<command>chmod</command> command, as
appropriate.</para></note>
<indexterm><primary>Tru64 UNIX</primary></indexterm>
<para>When this task has been completed, it is time to
initialize the NIS maps. FreeBSD includes a script named
<command>ypinit</command> to do this (see its
manual page for more information). Note that this script
is available on most &unix; Operating Systems, but not on
all. On Digital UNIX/Compaq Tru64 UNIX it is called
<command>ypsetup</command>. Because we are generating
maps for an NIS master, we are going to pass the
<option>-m</option> option to <command>ypinit</command>.
To generate the NIS maps run:</para>
<screen>ellington&prompt.root; <userinput>ypinit -m test-domain</userinput>
Server Type: MASTER Domain: test-domain
Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.
Do you want this procedure to quit on non-fatal errors? [y/n: n] <userinput>n</userinput>
Ok, please remember to go back and redo manually whatever fails.
If you don't, something might not work.
At this point, we have to construct a list of this domains YP servers.
rod.darktech.org is already known as master server.
Please continue to add any slave servers, one per line. When you are
done with the list, type a &lt;control D&gt;.
master server : ellington
next host to add: <userinput>coltrane</userinput>
next host to add: <userinput>^D</userinput>
The current list of NIS servers looks like this:
ellington
coltrane
Is this correct? [y/n: y] <userinput>y</userinput>
[..output from map generation..]
NIS Map update completed.
ellington has been setup as an YP master server without any errors.</screen>
<para>At this point, <command>ypinit</command> should have
created <filename>/var/yp/Makefile</filename> from
<filename>/var/yp/Makefile.dist</filename>.
When created, this file assumes that the operating
environment is a single server NIS system with only &os;
machines. Since <literal>test-domain</literal> has
a slave server as well, edit
<filename>/var/yp/Makefile</filename> as well:</para>
<screen>ellington&prompt.root; <userinput>vi /var/yp/Makefile</userinput></screen>
<para>You should comment out the line that says</para>
<programlisting>NOPUSH = "True"</programlisting>
<para>(if it is not commented out already).</para>
</sect4>
<sect4>
<title>Setting up a NIS Slave Server</title>
<indexterm>
<primary>NIS</primary>
<secondary>slave server</secondary>
</indexterm>
<para>Setting up an NIS slave server is even more simple
than setting up the master. Log on to the slave server
and edit the file <filename>/etc/rc.conf</filename> as you
did before. The only difference is that we now must use
the <option>-s</option> option when running
<command>ypinit</command>. The <option>-s</option> option
requires the name of the NIS master be passed to it as
well, so our command line looks like:</para>
<screen>coltrane&prompt.root; <userinput>ypinit -s ellington test-domain</userinput>
Server Type: SLAVE Domain: test-domain Master: ellington
Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.
Do you want this procedure to quit on non-fatal errors? [y/n: n] <userinput>n</userinput>
Ok, please remember to go back and redo manually whatever fails.
If you don't, something might not work.
There will be no further questions. The remainder of the procedure
should take a few minutes, to copy the databases from ellington.
Transferring netgroup...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byuser...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byhost...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring group.bygid...
ypxfr: Exiting: Map successfully transferred
Transferring group.byname...
ypxfr: Exiting: Map successfully transferred
Transferring services.byname...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.byname...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.byname...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring netid.byname...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring ypservers...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byname...
ypxfr: Exiting: Map successfully transferred
coltrane has been setup as an YP slave server without any errors.
Don't forget to update map ypservers on ellington.</screen>
<para>There should be a directory called
<filename>/var/yp/test-domain</filename>. Copies of the
NIS master server's maps should be in this directory. These
files must always be up to date. The
following <filename>/etc/crontab</filename> entries on
the slave servers should do the job:</para>
<programlisting>20 * * * * root /usr/libexec/ypxfr passwd.byname
21 * * * * root /usr/libexec/ypxfr passwd.byuid</programlisting>
<para>These two lines force the slave to sync its maps with
the maps on the master server. These entries are not
mandatory because the master server automatically attempts
to push any map changes to its slaves; however, due to
the importance of correct password information on other
clients depending on the slave server, it is recommended
to specifically force the password map updates frequently.
This is especially important on busy networks where map
updates might not always complete.</para>
<para>Now, run the command <command>/etc/netstart</command>
on the slave server as well, which again starts the NIS
server.</para>
</sect4>
</sect3>
<sect3>
<title>NIS Clients</title>
<para>An NIS client establishes what is called a binding to a
particular NIS server using the
<command>ypbind</command> daemon. The
<command>ypbind</command> command checks the system's default
domain (as set by the <command>domainname</command>
command), and begins broadcasting RPC requests on the local
network. These requests specify the name of the domain for
which <command>ypbind</command> is attempting to establish a
binding. If a server that has been configured to serve the
requested domain receives one of the broadcasts, it will
respond to <command>ypbind</command>, which will record the
server's address. If there are several servers available (a
master and several slaves, for example),
<command>ypbind</command> will use the address of the first
one to respond. From that point on, the client system will
direct all of its NIS requests to
that server. <command>ypbind</command> will
occasionally <quote>ping</quote> the server to make sure it
is still up and running. If it fails to receive a reply to
one of its pings within a reasonable amount of time,
<command>ypbind</command> will mark the domain as unbound
and begin broadcasting again in the hopes of locating
another server.</para>
<sect4>
<title>Setting Up a NIS Client</title>
<indexterm>
<primary>NIS</primary> <secondary>client
configuration</secondary>
</indexterm> <para>Setting up a FreeBSD machine to be a NIS
client is fairly straightforward.</para>
<procedure>
<step>
<para>Edit <filename>/etc/rc.conf</filename>
and add the following lines in order to set the NIS
domainname and start <command>ypbind</command> during
network startup:</para>
<programlisting>nisdomainname="test-domain"
nis_client_enable="YES"</programlisting>
</step>
<step>
<para>To import all possible password entries from the
NIS server, remove all user accounts from the
<filename>/etc/master.passwd</filename> file and use
<command>vipw</command> to add the following line to
the end of the file:</para>
<programlisting>+:::::::::</programlisting>
<note>
<para>This line will afford anyone with a valid
account in the NIS server's password maps an
account. There are many ways to configure the NIS
client by changing this line. See the
<link
linkend="network-netgroups">netgroups
section</link> below for more information. For more
detailed reading see O'Reilly's book on
<literal>Managing NFS and NIS</literal>.</para>
</note>
<note>
<para>Keep in mind that at least one local account (i.e.
not imported via NIS) must exist in
<filename>/etc/master.passwd</filename> and this
account should also be a member of the group
<groupname>wheel</groupname>. If there is something
wrong with NIS, this account can be used to log in
remotely, become <username>root</username>, and fix
things.</para>
</note>
</step>
<step>
<para>To import all possible group entries from the NIS
server, add this line to
<filename>/etc/group</filename>:</para>
<programlisting>+:*::</programlisting>
</step>
</procedure>
<para>To start the NIS client immediately, execute the
following commands as the superuser:</para>
<screen>&prompt.root; <userinput>/etc/netstart</userinput>
&prompt.root; <userinput>service ypbind start</userinput></screen>
<para>After completing these steps, the command,
<command>ypcat passwd</command>, should show the
server's passwd map.</para>
</sect4>
</sect3>
</sect2>
<sect2>
<title>NIS Security</title>
<para>In general, any remote user may issue an RPC to
&man.ypserv.8; and retrieve the contents of the NIS maps,
provided the remote user knows the domainname. To prevent
such unauthorized transactions, &man.ypserv.8; supports a
feature called <quote>securenets</quote> which can be used to
restrict access to a given set of hosts. At startup,
&man.ypserv.8; will attempt to load the securenets information
from a file called
<filename>/var/yp/securenets</filename>.</para>
<note>
<para>This path varies depending on the path specified with
the <option>-p</option> option. This file contains entries
that consist of a network specification and a network mask
separated by white space. Lines starting with
<quote>#</quote> are considered to be comments. A sample
securenets file might look like this:</para>
</note>
<programlisting># allow connections from local host -- mandatory
127.0.0.1 255.255.255.255
# allow connections from any host
# on the 192.168.128.0 network
192.168.128.0 255.255.255.0
# allow connections from any host
# between 10.0.0.0 to 10.0.15.255
# this includes the machines in the testlab
10.0.0.0 255.255.240.0</programlisting>
<para>If &man.ypserv.8; receives a request from an address that
matches one of these rules, it will process the request
normally. If the address fails to match a rule, the request
will be ignored and a warning message will be logged. If the
<filename>/var/yp/securenets</filename> file does not exist,
<command>ypserv</command> will allow connections from any
host.</para>
<para>The <command>ypserv</command> program also has support for
Wietse Venema's <application>TCP Wrapper</application>
package. This allows the administrator to use the
<application>TCP Wrapper</application> configuration files for
access control instead of
<filename>/var/yp/securenets</filename>.</para>
<note>
<para>While both of these access control mechanisms provide
some security, they, like the privileged port test, are
vulnerable to <quote>IP spoofing</quote> attacks. All
NIS-related traffic should be blocked at the
firewall.</para>
<para>Servers using <filename>/var/yp/securenets</filename>
may fail to serve legitimate NIS clients with archaic TCP/IP
implementations. Some of these implementations set all host
bits to zero when doing broadcasts and/or fail to observe
the subnet mask when calculating the broadcast address.
While some of these problems can be fixed by changing the
client configuration, other problems may force
the retirement of the client systems in question or the
abandonment of
<filename>/var/yp/securenets</filename>.</para>
<para>Using <filename>/var/yp/securenets</filename> on a
server with such an archaic implementation of TCP/IP is a
really bad idea and will lead to loss of NIS functionality
for large parts of the network.</para>
<indexterm><primary>TCP Wrappers</primary></indexterm>
<para>The use of <application>TCP Wrapper</application>
increases the latency of the NIS server. The
additional delay may be long enough to cause timeouts in
client programs, especially in busy networks or with slow
NIS servers. If one or more of the client systems
suffers from these symptoms, convert the client
systems in question into NIS slave servers and force them
to bind to themselves.</para>
</note>
</sect2>
<sect2>
<title>Barring Some Users from Logging On</title>
<para>In our lab, there is a machine <hostid>basie</hostid> that
is supposed to be a faculty only workstation. We do not want
to take this machine out of the NIS domain, yet the
<filename>passwd</filename> file on the master NIS server
contains accounts for both faculty and students. What can we
do?</para>
<para>There is a way to bar specific users from logging on to a
machine, even if they are present in the NIS database. To do
this, add
<literal>-<replaceable>username</replaceable></literal> with
the correct number of colons like other entries to the
end of the <filename>/etc/master.passwd</filename> file on the
client machine, where <replaceable>username</replaceable> is
the username of the user to bar from logging in.
The line with the blocked user must be before the
<literal>+</literal> line for allowing NIS users.
This should preferably be done using <command>vipw</command>,
since <command>vipw</command> will sanity check the changes
to <filename>/etc/master.passwd</filename>, as well as
automatically rebuild the password database after
editing. For example, to bar user
<username>bill</username> from logging on to
<hostid>basie</hostid>:</para>
<screen>basie&prompt.root; <userinput>vipw</userinput>
<userinput>[add -bill::::::::: to the end, exit]</userinput>
vipw: rebuilding the database...
vipw: done
basie&prompt.root; <userinput>cat /etc/master.passwd</userinput>
root:[password]:0:0::0:0:The super-user:/root:/bin/csh
toor:[password]:0:0::0:0:The other super-user:/root:/bin/sh
daemon:*:1:1::0:0:Owner of many system processes:/root:/sbin/nologin
operator:*:2:5::0:0:System &amp;:/:/sbin/nologin
bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/sbin/nologin
tty:*:4:65533::0:0:Tty Sandbox:/:/sbin/nologin
kmem:*:5:65533::0:0:KMem Sandbox:/:/sbin/nologin
games:*:7:13::0:0:Games pseudo-user:/usr/games:/sbin/nologin
news:*:8:8::0:0:News Subsystem:/:/sbin/nologin
man:*:9:9::0:0:Mister Man Pages:/usr/share/man:/sbin/nologin
bind:*:53:53::0:0:Bind Sandbox:/:/sbin/nologin
uucp:*:66:66::0:0:UUCP pseudo-user:/var/spool/uucppublic:/usr/libexec/uucp/uucico
xten:*:67:67::0:0:X-10 daemon:/usr/local/xten:/sbin/nologin
pop:*:68:6::0:0:Post Office Owner:/nonexistent:/sbin/nologin
nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/sbin/nologin
-bill:::::::::
+:::::::::
basie&prompt.root;</screen>
</sect2>
<sect2 id="network-netgroups">
<sect2info>
<authorgroup>
<author>
<firstname>Udo</firstname>
<surname>Erdelhoff</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect2info>
<title>Using Netgroups</title>
<indexterm><primary>netgroups</primary></indexterm>
<para>The method shown in the previous section works reasonably
well for special rules in an environment with small numbers of
users and/or machines. On larger networks, administrators
<emphasis>will</emphasis> likely forget to bar some users from
logging onto sensitive machines, or may even have to
modify each machine separately, thus losing the main benefit
of NIS: <emphasis>centralized</emphasis>
administration.</para>
<para>The NIS developers' solution for this problem is called
<emphasis>netgroups</emphasis>. Their purpose and semantics
can be compared to the normal groups used by &unix; file
systems. The main differences are the lack of a numeric ID
and the ability to define a netgroup by including both user
accounts and other netgroups.</para>
<para>Netgroups were developed to handle large, complex networks
with hundreds of users and machines. On one hand, this is a
Good Thing in such a situation.
On the other hand, this complexity makes it almost impossible
to explain netgroups with really simple examples. The example
used in the remainder of this section demonstrates this
problem.</para>
<para>Let us assume that the successful introduction of NIS in
the laboratory caught a superiors' interest. The next
task is to extend the NIS domain to cover some of the other
machines on campus. The two tables contain the names of the
new users and new machines as well as brief descriptions of
them.</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>User Name(s)</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><username>alpha</username>,
<username>beta</username></entry>
<entry>Normal employees of the IT department</entry>
</row>
<row>
<entry><username>charlie</username>,
<username>delta</username></entry>
<entry>The new apprentices of the IT department</entry>
</row>
<row>
<entry><username>echo</username>,
<username>foxtrott</username>,
<username>golf</username>, ...</entry>
<entry>Ordinary employees</entry>
</row>
<row>
<entry><username>able</username>,
<username>baker</username>, ...</entry>
<entry>The current interns</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>Machine Name(s)</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<!-- Names taken from "Good Omens" by Neil Gaiman and Terry
Pratchett. Many thanks for a brilliant book. -->
<entry><hostid>war</hostid>,
<hostid>death</hostid>, <hostid>famine</hostid>,
<hostid>pollution</hostid></entry>
<entry>The most important servers deployed. Only the IT
employees are allowed to log onto these
machines.</entry>
</row>
<row>
<!-- gluttony was omitted because it was too fat -->
<entry><hostid>pride</hostid>, <hostid>greed</hostid>,
<hostid>envy</hostid>, <hostid>wrath</hostid>,
<hostid>lust</hostid>, <hostid>sloth</hostid></entry>
<entry>Less important servers. All members of the IT
department are allowed to login onto these
machines.</entry>
</row>
<row>
<entry><hostid>one</hostid>, <hostid>two</hostid>,
<hostid>three</hostid>, <hostid>four</hostid>,
...</entry>
<entry>Ordinary workstations. Only the
<emphasis>real</emphasis> employees are allowed to use
these machines.</entry>
</row>
<row>
<entry><hostid>trashcan</hostid></entry>
<entry>A very old machine without any critical data.
Even the intern is allowed to use this box.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>An attempt to implement these restrictions by separately
blocking each user, would require the addition of the
<literal>-<replaceable>user</replaceable></literal> line to
each system's <filename>passwd</filename>. One line for each user
who is not allowed to login onto that system. Forgetting just one
entry could cause significant trouble. It may be feasible to
do this correctly during the initial setup; however, eventually
someone will forget to add these lines
for new users.</para>
<para>Handling this situation with netgroups offers several
advantages. Each user need not be handled separately; they
would be assigned to one or more netgroups and logins would
be allowed or forbidden for all members of the netgroup.
While adding a new
machine, login restrictions must be defined for all
netgroups. If a new user is added, they must be added
to one or more netgroups. Those changes are
independent of each other: no more <quote>for each combination
of user and machine do...</quote> If the NIS setup is planned
carefully, only one central configuration file
needs modification to grant or deny access to machines.</para>
<para>The first step is the initialization of the NIS map
netgroup. &os;'s &man.ypinit.8; does not create this map
by default, but its NIS implementation will support it
after creation. To create an empty map, simply type</para>
<screen>ellington&prompt.root; <userinput>vi /var/yp/netgroup</userinput></screen>
<para>and begin adding content. For our example, we need at
least four netgroups: IT employees, IT apprentices, normal
employees and interns.</para>
<programlisting>IT_EMP (,alpha,test-domain) (,beta,test-domain)
IT_APP (,charlie,test-domain) (,delta,test-domain)
USERS (,echo,test-domain) (,foxtrott,test-domain) \
(,golf,test-domain)
INTERNS (,able,test-domain) (,baker,test-domain)</programlisting>
<para><literal>IT_EMP</literal>, <literal>IT_APP</literal> etc.
are the names of the netgroups. Each bracketed group adds
one or more user accounts to it. The three fields inside a
group are:</para>
<orderedlist>
<listitem>
<para>The name of the host(s) where the following items are
valid. If a hostname is not specified, the entry is
valid on all hosts. If a hostname is specified, it
will need to be micro-managed within this
configuration.</para>
</listitem>
<listitem>
<para>The name of the account that belongs to this
netgroup.</para>
</listitem>
<listitem>
<para>The NIS domain for the account. Accounts may be
imported from other NIS domains into a netgroup.</para>
</listitem>
</orderedlist>
<para>Each of these fields may contain wildcards. See
&man.netgroup.5; for details.</para>
<note>
<indexterm><primary>netgroups</primary></indexterm>
<para>Netgroup names longer than 8 characters should not be
used, especially with machines running other
operating systems within the NIS domain. The names are
case sensitive; using capital letters for netgroup
names is an easy way to distinguish between user, machine
and netgroup names.</para>
<para>Some NIS clients (other than &os;) cannot handle
netgroups with a large number of entries. For example, some
older versions of &sunos; start to cause trouble if a
netgroup contains more than 15 <emphasis>entries</emphasis>.
This limit may be circumvented by creating several
sub-netgroups with 15 users or fewer and a real netgroup
consisting of the sub-netgroups:</para>
<programlisting>BIGGRP1 (,joe1,domain) (,joe2,domain) (,joe3,domain) [...]
BIGGRP2 (,joe16,domain) (,joe17,domain) [...]
BIGGRP3 (,joe31,domain) (,joe32,domain)
BIGGROUP BIGGRP1 BIGGRP2 BIGGRP3</programlisting>
<para>Repeat this process if more than 225
users will exist within a single netgroup.</para>
</note>
<para>Activating and distributing the new NIS map is
easy:</para>
<screen>ellington&prompt.root; <userinput>cd /var/yp</userinput>
ellington&prompt.root; <userinput>make</userinput></screen>
<para>This will generate the three NIS maps
<filename>netgroup</filename>,
<filename>netgroup.byhost</filename> and
<filename>netgroup.byuser</filename>. Use &man.ypcat.1; to
check if the new NIS maps are available:</para>
<screen>ellington&prompt.user; <userinput>ypcat -k netgroup</userinput>
ellington&prompt.user; <userinput>ypcat -k netgroup.byhost</userinput>
ellington&prompt.user; <userinput>ypcat -k netgroup.byuser</userinput></screen>
<para>The output of the first command should resemble the
contents of <filename>/var/yp/netgroup</filename>. The second
command will not produce output without specified
host-specific netgroups. The third command may be used to
get the list of netgroups for a user.</para>
<para>The client setup is quite simple. To configure the server
<hostid>war</hostid>, use
&man.vipw.8; to replace the line</para>
<programlisting>+:::::::::</programlisting>
<para>with</para>
<programlisting>+@IT_EMP:::::::::</programlisting>
<para>Now, only the data for the users defined in the netgroup
<literal>IT_EMP</literal> is imported into
<hostid>war</hostid>'s password database and only
these users are allowed to login.</para>
<para>Unfortunately, this limitation also applies to the
<literal>~</literal> function of the shell and all routines
converting between user names and numerical user IDs. In
other words, <command>cd
~<replaceable>user</replaceable></command> will not work,
<command>ls -l</command> will show the numerical ID instead of
the username and <command>find . -user joe -print</command>
will fail with <errorname>No such user</errorname>. To fix
this, import all user entries
<emphasis>without allowing them to login into the
servers</emphasis>.</para>
<para>This can be achieved by adding another line to
<filename>/etc/master.passwd</filename>. This line should
contain:</para>
<para><literal>+:::::::::/sbin/nologin</literal>, meaning
<quote>Import all entries but replace the shell with
<filename>/sbin/nologin</filename> in the imported
entries</quote>. It is possible to replace any field in the
<literal>passwd</literal> entry by placing a default value in
<filename>/etc/master.passwd</filename>.</para>
<!-- Been there, done that, got the scars to prove it - ue -->
<warning>
<para>Make sure that the line
<literal>+:::::::::/sbin/nologin</literal> is placed after
<literal>+@IT_EMP:::::::::</literal>. Otherwise, all user
accounts imported from NIS will have
<filename>/sbin/nologin</filename> as their login
shell.</para>
</warning>
<para>After this change, the NIS map will only need modification
when a new employee joins the IT department. A similar approach
for the less important servers may be used by replacing
the old <literal>+:::::::::</literal> in their local version
of <filename>/etc/master.passwd</filename> with something like
this:</para>
<programlisting>+@IT_EMP:::::::::
+@IT_APP:::::::::
+:::::::::/sbin/nologin</programlisting>
<para>The corresponding lines for the normal workstations
could be:</para>
<programlisting>+@IT_EMP:::::::::
+@USERS:::::::::
+:::::::::/sbin/nologin</programlisting>
<para>And everything would be fine until there is a policy
change a few weeks later: The IT department starts hiring
interns. The IT interns are allowed to use the normal
workstations and the less important servers; and the IT
apprentices are allowed to login onto the main servers.
Add a new netgroup <literal>IT_INTERN</literal>, then add the
new IT interns to this netgroup and start to change the
configuration on each and every machine. As the old saying
goes: <quote>Errors in centralized planning lead to global
mess</quote>.</para>
<para>NIS' ability to create netgroups from other netgroups can
be used to prevent situations like these. One possibility is
the creation of role-based netgroups. For example, one might
create a netgroup called <literal>BIGSRV</literal> to define
the login restrictions for the important servers, another
netgroup called <literal>SMALLSRV</literal> for the less
important servers and a third netgroup called
<literal>USERBOX</literal> for the normal
workstations. Each of these netgroups contains the netgroups
that are allowed to login onto these machines. The new
entries for the NIS map netgroup should look like
this:</para>
<programlisting>BIGSRV IT_EMP IT_APP
SMALLSRV IT_EMP IT_APP ITINTERN
USERBOX IT_EMP ITINTERN USERS</programlisting>
<para>This method of defining login restrictions works
reasonably well when it is possible to define groups of machines
with identical restrictions. Unfortunately, this is the
exception and not the rule. Most of the time, the ability
to define login restrictions on a per-machine basis is
required.</para>
<para>Machine-specific netgroup definitions are the other
possibility to deal with the policy change outlined above. In
this scenario, the <filename>/etc/master.passwd</filename> of
each box contains two lines starting with <quote>+</quote>.
The first of them adds a netgroup with the accounts allowed to
login onto this machine, the second one adds all other
accounts with <filename>/sbin/nologin</filename> as shell. It
is a good idea to use the <quote>ALL-CAPS</quote> version of
the machine name as the name of the netgroup. In other words,
the lines should look like this:</para>
<programlisting>+@<replaceable>BOXNAME</replaceable>:::::::::
+:::::::::/sbin/nologin</programlisting>
<para>Once this task is completed on all the machines,
there is no longer a need to modify the local versions of
<filename>/etc/master.passwd</filename> ever again. All
further changes can be handled by modifying the NIS map. Here
is an example of a possible netgroup map for this
scenario with some additional goodies:</para>
<programlisting># Define groups of users first
IT_EMP (,alpha,test-domain) (,beta,test-domain)
IT_APP (,charlie,test-domain) (,delta,test-domain)
DEPT1 (,echo,test-domain) (,foxtrott,test-domain)
DEPT2 (,golf,test-domain) (,hotel,test-domain)
DEPT3 (,india,test-domain) (,juliet,test-domain)
ITINTERN (,kilo,test-domain) (,lima,test-domain)
D_INTERNS (,able,test-domain) (,baker,test-domain)
#
# Now, define some groups based on roles
USERS DEPT1 DEPT2 DEPT3
BIGSRV IT_EMP IT_APP
SMALLSRV IT_EMP IT_APP ITINTERN
USERBOX IT_EMP ITINTERN USERS
#
# And a groups for a special tasks
# Allow echo and golf to access our anti-virus-machine
SECURITY IT_EMP (,echo,test-domain) (,golf,test-domain)
#
# machine-based netgroups
# Our main servers
WAR BIGSRV
FAMINE BIGSRV
# User india needs access to this server
POLLUTION BIGSRV (,india,test-domain)
#
# This one is really important and needs more access restrictions
DEATH IT_EMP
#
# The anti-virus-machine mentioned above
ONE SECURITY
#
# Restrict a machine to a single user
TWO (,hotel,test-domain)
# [...more groups to follow]</programlisting>
<para>If some kind of database is used to manage the user
accounts, it may be possible to create the first part of the
map using the database's reporting tools. This way, new users
will automatically have access to the boxes.</para>
<para>One last word of caution: It may not always be advisable
to use machine-based netgroups. When deploying a couple
of dozen or even hundreds of identical machines for student
labs, role-based netgroups instead of
machine-based netgroups may be used to keep the size of the NIS
map within reasonable limits.</para>
</sect2>
<sect2>
<title>Important Things to Remember</title>
<para>There are still a couple of things administrators need to
do differently now that machines are in an NIS
environment.</para>
<itemizedlist>
<listitem>
<para>Every time a new user is added to the lab, they
must be added to the master NIS server
and the <acronym>NIS</acronym> maps will need rebuilt. If
this step is omitted, the new user will not be able to login
anywhere except on the NIS master. For example, if we
needed to add a new user <username>jsmith</username> to
the lab, we would:</para>
<screen>&prompt.root; <userinput>pw useradd jsmith</userinput>
&prompt.root; <userinput>cd /var/yp</userinput>
&prompt.root; <userinput>make test-domain</userinput></screen>
<para>The user may also be added using
<command>adduser jsmith</command>
instead of <command>pw useradd jsmith</command>.</para>
</listitem>
<listitem>
<para><emphasis>Keep the administration accounts out of the
NIS maps</emphasis>. This is undesirable as it will
create a security risk. These users and passwords should
not be propagated to all machines. Especially if these
machines will have users whom should not have access to
those accounts.</para>
</listitem>
<listitem>
<para><emphasis>Keep the NIS master and slave secure, and
minimize their downtime</emphasis>. If somebody either
hacks or simply turns off these machines, they have
effectively rendered many people without the ability to
login to the lab.</para>
<para>This is the chief weakness of any centralized
administration system. If the NIS servers are not
protected, there will be a lot of angry users and
unhappy management!</para>
</listitem>
</itemizedlist>
</sect2>
<sect2>
<title>NIS v1 Compatibility</title>
<para>&os;'s <application>ypserv</application> has some
support for serving NIS v1 clients. &os;'s NIS
implementation only uses the NIS v2 protocol; however, other
implementations include support for the v1 protocol for
backwards compatibility with older systems. The
<application>ypbind</application> daemons supplied with these
systems will attempt to establish a binding to an NIS v1 server
even though they may never actually need it (and they may
persist in broadcasting in search of one even after they
receive a response from a v2 server). Note that while support
for normal client calls is provided, this version of
<application>ypserv</application> does not handle v1 map
transfer requests. Additionally, it cannot be used as a master
or slave in conjunction with older NIS servers that only
support the v1 protocol. Fortunately, there probably are not
any such servers still in use today.</para>
</sect2>
<sect2 id="network-nis-server-is-client">
<title>NIS Servers That Are Also NIS Clients</title>
<para>Care must be taken when running
<application>ypserv</application> in a multi-server domain
where the server machines are also NIS clients. It is
generally a good idea to force the servers to bind to
themselves rather than allowing them to broadcast bind
requests and possibly become bound to each other. Strange
failure modes can result if one server goes down and others
are dependent upon it. Eventually all the clients will time
out and attempt to bind to other servers, but the delay
involved can be considerable and the failure mode is still
present since the servers might bind to each other all over
again.</para>
<para>A host may be forced to bind to a particular server by
running <command>ypbind</command> with the <option>-S</option>
flag. Add the following lines to
<filename>/etc/rc.conf</filename> to enable this feature
during every system boot:</para>
<programlisting>nis_client_enable="YES" # run client stuff as well
nis_client_flags="-S <replaceable>NIS domain</replaceable>,<replaceable>server</replaceable>"</programlisting>
<para>See &man.ypbind.8; for further information.</para>
</sect2>
<sect2>
<title>Password Formats</title>
<indexterm>
<primary>NIS</primary>
<secondary>password formats</secondary>
</indexterm>
<para>One of the most common issues that people run into when
trying to implement NIS is password format compatibility. If
the NIS server is using DES encrypted passwords, it will only
support clients that are also using DES. For example, if any
&solaris; NIS clients exist on the network, there is a highly
likelihood DES must be used for encrypted passwords.</para>
<para>To check which format the servers and clients are using,
look at <filename>/etc/login.conf</filename>. If the host is
configured to use DES encrypted passwords, then the
<literal>default</literal> class will contain an entry like
this:</para>
<programlisting>default:\
:passwd_format=des:\
:copyright=/etc/COPYRIGHT:\
[Further entries elided]</programlisting>
<para>Other possible values for the
<literal>passwd_format</literal> capability include
<literal>blf</literal> and <literal>md5</literal> (for
Blowfish and MD5 encrypted passwords, respectively).</para>
<para>If any changes were made to
<filename>/etc/login.conf</filename>, the
login capability database must be rebuilt by
running the following command as
<username>root</username>:</para>
<screen>&prompt.root; <userinput>cap_mkdb /etc/login.conf</userinput></screen>
<note><para>The format of passwords already in
<filename>/etc/master.passwd</filename> will not be updated
until a user changes his password for the first time
<emphasis>after</emphasis> the login capability database is
rebuilt.</para></note>
<para>Next, in order to ensure that passwords are encrypted with
the chosen format, check that
the <literal>crypt_default</literal> in
<filename>/etc/auth.conf</filename> gives precedence to the
chosen password format. To do this, place the chosen format
first in the list. For example, when using DES
encrypted passwords, the entry would be:</para>
<programlisting>crypt_default = des blf md5</programlisting>
<para>Having followed the above steps on each of the &os; based
NIS servers and clients, verify that they all agree
on which password format is used within the network. If users
have trouble authenticating on an NIS client, this is a pretty
good place to start looking for possible problems. Remember:
to deploy an NIS server for a heterogeneous
network, they will probably have to use DES on all systems
because it is the lowest common standard.</para>
</sect2>
</sect1>
<sect1 id="network-ldap">
<sect1info>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</sect1info>
<title>&os; and <acronym>LDAP</acronym></title>
<indexterm><primary>LDAP</primary></indexterm>
<para><acronym>LDAP</acronym>, the Lightweight Directory Access
Protocol, is an application layer protocol used to access,
modify, and authenticate (bind) using a distributed directory
information service. Think of it as a phone or record book which
stores several levels of hierarchical, homogeneous information.
It is often used in networks where users often need access to
several levels of internal information utilizing a single
account. For example, email authentication, pulling employee
contact information, and internal website authentication might
all make use of a single user in the <acronym>LDAP</acronym>
server's record base.</para>
<para>This section will not provide a history or the implementation
details of the protocol. These sections were authored to get an
<acronym>LDAP</acronym> server and/or client configured both
quickly and securely; however, any information base requires
planning and this is no exception.</para>
<para>Planning should include what type of information will be
stored, what that information will be used for, whom should
have access to said information, and how to secure this
information from prying eyes.</para>
<sect2>
<title><acronym>LDAP</acronym> Terminology and Structure</title>
<para>Before continuing, several parts of <acronym>LDAP</acronym>
must be explained to prevent confusion. And confusion with
this configuration is relatively simple. To begin, all
directory entries consist of a group of
<emphasis>attributes</emphasis>. Each of these attribute sets
contain a name, a unique identifier known as a
<acronym>DN</acronym> or distinguished name normally built from
several other attributes such as the <acronym>RDN</acronym>.
The <acronym>RDN</acronym> or relative distinguished name, is
a more common name for the attribute. Like directories have
absolute and relative paths, consider a <acronym>DN</acronym>
as an absolute path and the <acronym>RDN</acronym> as the
relative path.</para>
<para>As an example, an entry might look like the
following:</para>
<screen>&prompt.user; ldapsearch -xb "uid=trhodes,ou=users,o=example.com"</screen>
<programlisting># extended LDIF
#
# LDAPv3
# base &lt;uid=trhodes,ou=users,o=example.com&gt; with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# trhodes, users, example.com
dn: uid=trhodes,ou=users,o=example.com
mail: trhodes@example.com
cn: Tom Rhodes
uid: trhodes
telephoneNumber: (xxx) xxx-xxxx
# search result
search: 2
result: 0 Success
# numResponses: 2
# numEntries: 1</programlisting>
<para>In this example, it is very obvious what the various
attributes are; however, the <acronym>cn</acronym> attribute
should be noticed. This is the <acronym>RDN</acronym> discussed
previously. In addition, there is a unique user id provided
here. It is common practice to have specific uid or uuids for
entries to ease in any future migration.</para>
</sect2>
<sect2>
<title>Configuring an <acronym>LDAP</acronym> Server</title>
<indexterm><primary>LDAP Server</primary></indexterm>
<para>To configure &os; to act as an <acronym>LDAP</acronym>
server, the OpenLDAP port needs installed. This may be
accomplished using the <command>pkg_add</command> command
or by installing the
<filename role="port">net/openldap24-server</filename>
port. Building the port is recommended as the administrator
may select a great deal of options at this time and disable
some options. In most cases, the defaults will be fine;
however, this is the time to enable SQL support if
needed.</para>
<para>A few directories will be required from this point on,
at minimal, a data directory and a directory to store the
certificates in. Create them both with the following
commands:</para>
<screen>&prompt.root; <userinput>mkdir /var/db/openldap-data</userinput></screen>
<screen>&prompt.root; <userinput>mkdir /usr/local/etc/openldap/private</userinput></screen>
<para>Copy over the database configuration file:</para>
<screen>&prompt.root; <userinput>cp /usr/local/etc/openldap/DB_CONFIG.example /var/db/openldap-data/DB_CONFIG</userinput></screen>
<para>The next phase is to configure the <acronym>SSL</acronym>
certificates. While creating certificates is discussed in
the <link linkend="openssl">OpenSSL</link> section in this
book, a certificate authority is needed so a different method
will be used. It is recommended that this section be reviewed
prior to configuring to ensure correct information is entered
during the certificate creation process below.</para>
<para>The following commands must be executed in the
<filename class="directory">
/usr/local/etc/openldap/private</filename> directory. This
is important as the file permissions will need to be restrictive
and users should not have access to these files directly. To
create the certificates, issues the following commands.</para>
<screen>&prompt.root; <userinput>openssl req -days 365 -nodes -new -x509 -keyout ca.key -out ../ca.crt</userinput></screen>
<para>The entries for these may be completely generic
<emphasis>except</emphasis> for the
<emphasis>Common Name</emphasis> entry. This entry must have
something different than the system hostname. If the entry
is the hostname, it would be like the hostname is attempting
to verify hostname. In cases with a self signed certificate
like this example, just prefix the hostname with
<acronym>CA</acronym> for certificate authority.</para>
<para>The next task is to create a certificate signing request
and a private key. To do this, issue the following
commands:</para>
<screen>&prompt.root; <userinput>openssl req -days 365 -nodes -new -keyout server.key -out server.csr</userinput></screen>
<para>During the certificate generation process, be sure to
correctly set the common name attribute. After this has
been completed, the key will need signed:</para>
<screen>&prompt.root; <userinput>openssl x509 -req -days 365 -in server.csr -out ../server.crt -CA ../ca.crt -CAkey ca.key -CAcreateserial</userinput></screen>
<para>The final part of the certificate generation process
is to generate and sign the client certificates:</para>
<screen>&prompt.root; <userinput>openssl req -days 365 -nodes -new -keyout client.key -out client.csr</userinput></screen>
<screen>&prompt.root; <userinput>openssl x509 -req -days 3650 -in client.csr -out ../client.crt -CA ../ca.crt -CAkey ca.key</userinput></screen>
<para>Remember, again, to respect the common name attribute. This
is a common cause for confusion during the first attempt to
configure <acronym>LDAP</acronym>. In addition, ensure that
a total of eight (8) new files have been generated through
the proceeding commands. If so, the next step is to edit
<filename>/usr/local/etc/openldap/slapd.conf</filename> and add
the following options:</para>
<programlisting>TLSCipherSuite HIGH:MEDIUM:+SSLv3
TLSCertificateFile /usr/local/etc/openldap/server.crt
TLSCertificateKeyFile /usr/local/etc/openldap/private/server.key
TLSCACertificateFile /usr/local/etc/openldap/ca.crt</programlisting>
<para>In addition, edit
<filename>/usr/local/etc/openldap/ldap.conf</filename> and
add the following lines:</para>
<programlisting>TLS_CACERT /usr/local/etc/openldap/ca.crt
TLS_CIPHER_SUITE HIGH:MEDIUM:+SSLv3</programlisting>
<para>While editing these this file, set the <option>BASE</option>
to the desired values, and uncomment all three of the
<option>URI</option>, <option>SIZELIMIT</option> and
<option>TIMELIMIT</option> options. In addition, set the
<option>URI</option> to contain <option>ldap://</option>
and <option>ldaps://</option>.</para>
<para>The resulting file should look similar to the following
shown here:</para>
<programlisting>BASE dc=example,dc=com
URI ldap:// ldaps://
SIZELIMIT 12
TIMELIMIT 15
#DEREF never
TLS_CACERT /usr/local/etc/openldap/ca.crt
TLS_CIPHER_SUITE HIGH:MEDIUM:+SSLv3</programlisting>
<para>A password for the server will need to be created as the
default is extremely poor as is normal in this industry. To
do this, issue the following command, sending the output to
<filename>slapd.conf</filename>:</para>
<screen>&prompt.root; <userinput>slappasswd -h "{SHA}" &gt;&gt; /usr/local/etc/openldap/slapd.conf</userinput></screen>
<para>There will be a prompt for entering the password and,
if the process does not fail, a password hash will be added
to the end of <filename>slapd.conf</filename>. The
<command>slappasswd</command> understands several hashing
formats, refer to the manual page for more information.</para>
<para>Edit <filename>/usr/local/etc/openldap/slapd.conf</filename>
and add the following lines:</para>
<programlisting>password-hash {sha}
allow bind_v2</programlisting>
<para>In addition, the <option>suffix</option> in this file must
be updated to match the <option>BASE</option> from the previous
configuration. The <option>rootdn</option> option should
also be set. A good recommendation is something like
<option>cn=Manager</option>. Before saving this file, place
the <option>rootpw</option> option in front of the password
output from the <command>slappasswd</command> and delete the
old <option>rootpw</option> option above. The end result
should look similar to this:</para>
<programlisting>TLSCipherSuite HIGH:MEDIUM:+SSLv3
TLSCertificateFile /usr/local/etc/openldap/server.crt
TLSCertificateKeyFile /usr/local/etc/openldap/private/server.key
TLSCACertificateFile /usr/local/etc/openldap/ca.crt
rootpw {SHA}W6ph5Mm5Pz8GgiULbPgzG37mj9g=</programlisting>
<para>Finally, enable the <application>OpenLDAP</application>
service in <filename>rc.conf</filename>. At this time,
setting up a <acronym>URI</acronym> and providing the group
and user to run as may be useful.
Edit <filename>/etc/rc.conf</filename> and add the following
lines:</para>
<programlisting>slapd_enable="YES"
slapd_flags="-4 -h ldaps:///"</programlisting>
<para>At this point the server should be ready to be brought
up and tested. To perform this task, issue the following
command:</para>
<screen>&prompt.root; <userinput>service slapd start</userinput></screen>
<para>If everything was configured correctly, a search of the
directory should show a successful connection with a single
response as in this example:</para>
<screen>&prompt.root; <userinput>ldapsearch -Z</userinput></screen>
<programlisting># extended LDIF
#
# LDAPv3
# base &lt;dc=example,dc=com&gt; (default) with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# search result
search: 3
result: 32 No such object
# numResponses: 1</programlisting>
<para>Considering the service should now be responding, as it
is above, the directory may be populated using the
<command>ldapadd</command> command. In this example, there
is a file containing a list of users to be added to this
particular directory. First, create a file to be imported
with the following dataset:</para>
<programlisting>dn: dc=example,dc=com
objectclass: dcObject
objectclass: organization
o: Example
dc: Example
dn: cn=Manager,dc=example,dc=com
objectclass: organizationalRole
cn: Manager</programlisting>
<note>
<para>To debug any of the following, stop the
<command>slapd</command> service using the
<command>service</command> command and start it using with
debugging options. To accomplish this, issue the following
command:</para>
<screen>&prompt.root; <userinput>/usr/local/libexec/slapd -d -1</userinput></screen>
</note>
<para>To import this datafile, issue the following command,
assuming the file is <filename>import.ldif</filename>:</para>
<screen>&prompt.root; <userinput>ldapadd -Z -D "cn=Manager,dc=example,dc=com" -W -f <replaceable>import.ldif</replaceable></userinput></screen>
<para>There will be a request for the password specified earlier,
and the output should look like this:</para>
<screen>Enter LDAP Password:
adding new entry "dc=example,dc=com"
adding new entry "cn=Manager,dc=example,dc=com"</screen>
<para>Verify the data was added by issuing a search on the
server using <command>ldapsearch</command>. In this case
the output should look like this:</para>
<screen>&prompt.user; <userinput>ldapsearch -Z</userinput></screen>
<screen># extended LDIF
#
# LDAPv3
# base &lt;dc=example,dc=com&gt; (default) with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# example.com
dn: dc=example,dc=com
objectClass: dcObject
objectClass: organization
o: Example
dc: Example
# Manager, example.com
dn: cn=Manager,dc=example,dc=com
objectClass: organizationalRole
cn: Manager
# search result
search: 3
result: 0 Success
# numResponses: 3
# numEntries: 2</screen>
<para>It is of course advisable to read about the structure of
<acronym>LDAP</acronym> directories and the various manual
pages mentioned in this section. At this point, the server
should be configured and functioning properly.</para>
</sect2>
</sect1>
<sect1 id="network-dhcp">
<sect1info>
<authorgroup>
<author>
<firstname>Greg</firstname>
<surname>Sutter</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</sect1info>
<title>Automatic Network Configuration (DHCP)</title>
<sect2>
<title>What Is DHCP?</title>
<indexterm>
<primary>Dynamic Host Configuration Protocol</primary>
<see>DHCP</see>
</indexterm>
<indexterm>
<primary>Internet Systems Consortium (ISC)</primary>
</indexterm>
<para>DHCP, the Dynamic Host Configuration Protocol, describes
the means by which a system can connect to a network and
obtain the necessary information for communication upon that
network. FreeBSD uses the OpenBSD <command>dhclient</command>
taken from OpenBSD&nbsp;3.7. All information here regarding
<command>dhclient</command> is for use with either of the ISC
or OpenBSD DHCP clients. The DHCP server is the one included
in the ISC distribution.</para>
</sect2>
<sect2>
<title>What This Section Covers</title>
<para>This section describes both the client-side components of
the ISC and OpenBSD DHCP client and server-side components of
the ISC DHCP system. The client-side program,
<command>dhclient</command>, comes integrated within FreeBSD,
and the server-side portion is available from the <filename
role="package">net/isc-dhcp42-server</filename> port. The
&man.dhclient.8;, &man.dhcp-options.5;, and
&man.dhclient.conf.5; manual pages, in addition to the
references below, are useful resources.</para>
</sect2>
<sect2>
<title>How It Works</title>
<indexterm><primary>UDP</primary></indexterm>
<para>When <command>dhclient</command>, the DHCP client, is
executed on the client machine, it begins broadcasting
requests for configuration information. By default, these
requests are on UDP port 68. The server replies on UDP 67,
giving the client an IP address and other relevant network
information such as netmask, router, and DNS servers. All of
this information comes in the form of a DHCP
<quote>lease</quote> and is only valid for a certain time
(configured by the DHCP server maintainer). In this manner,
stale IP addresses for clients no longer connected to the
network can be automatically reclaimed.</para>
<para>DHCP clients can obtain a great deal of information from
the server. An exhaustive list may be found in
&man.dhcp-options.5;.</para>
</sect2>
<sect2>
<title>FreeBSD Integration</title>
<para>&os; fully integrates the OpenBSD DHCP client,
<command>dhclient</command>. DHCP client support is provided
within both the installer and the base system, obviating the
need for detailed knowledge of network configurations on any
network that runs a DHCP server.</para>
<indexterm>
<primary><application>sysinstall</application></primary>
</indexterm>
<para>DHCP is supported by
<application>sysinstall</application>. When configuring a
network interface within
<application>sysinstall</application>, the second question
asked is: <quote>Do you want to try DHCP configuration of
the interface?</quote>. Answering affirmatively will
execute <command>dhclient</command>, and if successful, will
fill in the network configuration information
automatically.</para>
<para>There are two things required to have the system use
DHCP upon startup:</para>
<indexterm>
<primary>DHCP</primary>
<secondary>requirements</secondary>
</indexterm>
<itemizedlist>
<listitem>
<para>Make sure that the <devicename>bpf</devicename>
device is compiled into the kernel. To do this, add
<literal>device bpf</literal> to the kernel
configuration file, and rebuild the kernel. For more
information about building kernels, see <xref
linkend="kernelconfig"/>.</para> <para>The
<devicename>bpf</devicename> device is already part of
the <filename>GENERIC</filename> kernel that is supplied
with &os;, thus there is no need to build a custom kernel
for <acronym>DHCP</acronym>. In the case of a custom
kernel configuration file, this device must be present
for <acronym>DHCP</acronym> to function properly.</para>
<note>
<para>For those who are particularly security conscious,
take note that <devicename>bpf</devicename>
is also the device that allows packet sniffers to work
correctly (although they still have to be run as
<username>root</username>).
<devicename>bpf</devicename> <emphasis>is</emphasis>
required to use DHCP; however, the security sensitive
types should probably not add
<devicename>bpf</devicename> to the
kernel in the expectation that at some point in the
future the system will be using DHCP.</para>
</note>
</listitem>
<listitem>
<para>By default, DHCP configuration on &os; runs in the
background, or <firstterm>asynchronously</firstterm>.
Other startup scripts continue to run while DHCP
completes, speeding up system startup.</para>
<para>Background DHCP works well when the DHCP server
responds quickly to requests and the DHCP configuration
process goes quickly. However, DHCP may take a long
time to complete on some systems. If network services
attempt to run before DHCP has completed, they will
fail. Using DHCP in <firstterm>synchronous</firstterm>
mode prevents the problem, pausing startup until DHCP
configuration has completed.</para>
<para>To connect to a DHCP server in the background while
other startup continues (asynchronous mode), use the
<quote><literal>DHCP</literal></quote> value in
<filename>/etc/rc.conf</filename>:</para>
<programlisting>ifconfig_<replaceable>fxp0</replaceable>="DHCP"</programlisting>
<para>To pause startup while DHCP completes, use
synchronous mode with the
<quote><literal>SYNCDHCP</literal></quote> value:</para>
<programlisting>ifconfig_<replaceable>fxp0</replaceable>="SYNCDHCP"</programlisting>
<note>
<para>Replace the <replaceable>fxp0</replaceable> shown
in these examples with the name of the interface to be
dynamically configured, as described in
<xref linkend="config-network-setup"/>.</para>
</note>
<para>When using a different file system location for
<command>dhclient</command>, or if
additional flags must be passed to
<command>dhclient</command>,
include (editing as necessary):</para>
<programlisting>dhclient_program="/sbin/dhclient"
dhclient_flags=""</programlisting>
</listitem>
</itemizedlist>
<indexterm>
<primary>DHCP</primary>
<secondary>server</secondary>
</indexterm>
<para>The DHCP server, <application>dhcpd</application>, is
included as part of the <filename
role="package">net/isc-dhcp42-server</filename> port in
the ports collection. This port contains the ISC DHCP
server and documentation.</para>
</sect2>
<sect2>
<title>Files</title>
<indexterm>
<primary>DHCP</primary>
<secondary>configuration files</secondary>
</indexterm>
<itemizedlist>
<listitem>
<para><filename>/etc/dhclient.conf</filename></para>
<para><command>dhclient</command> requires a configuration
file, <filename>/etc/dhclient.conf</filename>.
Typically the file contains only comments, the defaults
being reasonably sane. This configuration file is
described by the &man.dhclient.conf.5; manual
page.</para>
</listitem>
<listitem>
<para><filename>/sbin/dhclient</filename></para>
<para><command>dhclient</command> is statically linked and
resides in <filename>/sbin</filename>. The
&man.dhclient.8; manual page gives more information
about <command>dhclient</command>.</para>
</listitem>
<listitem>
<para><filename>/sbin/dhclient-script</filename></para>
<para><command>dhclient-script</command> is the
FreeBSD-specific DHCP client configuration script. It
is described in &man.dhclient-script.8;, but should not
need any user modification to function properly.</para>
</listitem>
<listitem>
<para><filename>/var/db/dhclient.leases.<replaceable>interface</replaceable></filename></para>
<para>The DHCP client keeps a database of valid leases
in this file, which is written as a log.
&man.dhclient.leases.5; gives a slightly longer
description.</para>
</listitem>
</itemizedlist>
</sect2>
<sect2>
<title>Further Reading</title>
<para>The DHCP protocol is fully described in <ulink
url="http://www.freesoft.org/CIE/RFC/2131/">RFC
2131</ulink>. An informational resource has also been set
up at <ulink url="http://www.dhcp.org/"></ulink>.</para>
</sect2>
<sect2 id="network-dhcp-server">
<title>Installing and Configuring a DHCP Server</title>
<sect3>
<title>What This Section Covers</title>
<para>This section provides information on how to configure
a FreeBSD system to act as a DHCP server using the ISC
(Internet Systems Consortium) implementation of the DHCP
server.</para>
<para>The server is not provided as part of &os;, and so
the <filename
role="package">net/isc-dhcp42-server</filename> port must
be installed to provide this service.
See <xref linkend="ports"/> for
more information on using the Ports Collection.</para>
</sect3>
<sect3>
<title>DHCP Server Installation</title>
<indexterm>
<primary>DHCP</primary>
<secondary>installation</secondary>
</indexterm>
<para>In order to configure the &os; system as a DHCP
server, first ensure that the &man.bpf.4;
device is compiled into the kernel. To do this, add
<literal>device bpf</literal> to the kernel
configuration file, and rebuild the kernel. For more
information about building kernels, see <xref
linkend="kernelconfig"/>.</para>
<para>The <devicename>bpf</devicename> device is already
part of the <filename>GENERIC</filename> kernel that is
supplied with &os;, so there is no need to create a
custom kernel in order to get <acronym>DHCP</acronym>
working.</para>
<note>
<para>Those who are particularly security conscious
should note that <devicename>bpf</devicename> is also
the device that allows packet sniffers to function
correctly (although such programs still need
privileged access). The <devicename>bpf</devicename>
device <emphasis>is</emphasis> required to use DHCP, but
if the sensitivity of the system's security is high, this
device should not be included in
the kernel purely because the use of
<acronym>DHCP</acronym> may, at
some point in the future, be desired.</para>
</note>
<para>The next thing that is needed is to edit the
sample <filename>dhcpd.conf</filename> which was installed
by the <filename
role="package">net/isc-dhcp42-server</filename> port.
By default, this will be
<filename>/usr/local/etc/dhcpd.conf.sample</filename>, and
you should copy this to
<filename>/usr/local/etc/dhcpd.conf</filename> before
proceeding to make changes.</para>
</sect3>
<sect3>
<title>Configuring the DHCP Server</title>
<indexterm>
<primary>DHCP</primary>
<secondary>dhcpd.conf</secondary>
</indexterm>
<para><filename>dhcpd.conf</filename> is comprised of
declarations regarding subnets and hosts, and is perhaps
most easily explained using an example :</para>
<programlisting>option domain-name "example.com";<co id="domain-name"/>
option domain-name-servers 192.168.4.100;<co id="domain-name-servers"/>
option subnet-mask 255.255.255.0;<co id="subnet-mask"/>
default-lease-time 3600;<co id="default-lease-time"/>
max-lease-time 86400;<co id="max-lease-time"/>
ddns-update-style none;<co id="ddns-update-style"/>
subnet 192.168.4.0 netmask 255.255.255.0 {
range 192.168.4.129 192.168.4.254;<co id="range"/>
option routers 192.168.4.1;<co id="routers"/>
}
host mailhost {
hardware ethernet 02:03:04:05:06:07;<co id="hardware"/>
fixed-address mailhost.example.com;<co id="fixed-address"/>
}</programlisting>
<calloutlist>
<callout arearefs="domain-name">
<para>This option specifies the domain that will be
provided to clients as the default search domain. See
&man.resolv.conf.5; for more information on what this
means.</para>
</callout>
<callout arearefs="domain-name-servers">
<para>This option specifies a comma separated list of
DNS servers that the client should use.</para>
</callout>
<callout arearefs="subnet-mask">
<para>The netmask that will be provided to
clients.</para>
</callout>
<callout arearefs="default-lease-time">
<para>A client may request a specific length of time
that a lease will be valid. Otherwise the server will
assign a lease with this expiry value (in
seconds).</para>
</callout>
<callout arearefs="max-lease-time">
<para>This is the maximum length of time that the server
will lease for. Should a client request a longer
lease, a lease will be issued, although it will only
be valid for <literal>max-lease-time</literal>
seconds.</para>
</callout>
<callout arearefs="ddns-update-style">
<para>This option specifies whether the DHCP server
should attempt to update DNS when a lease is accepted
or released. In the ISC implementation, this option
is <emphasis>required</emphasis>.</para>
</callout>
<callout arearefs="range">
<para>This denotes which IP addresses should be used in
the pool reserved for allocating to clients. IP
addresses between, and including, the ones stated are
handed out to clients.</para>
</callout>
<callout arearefs="routers">
<para>Declares the default gateway that will be provided
to clients.</para>
</callout>
<callout arearefs="hardware">
<para>The hardware MAC address of a host (so that the
DHCP server can recognize a host when it makes a
request).</para>
</callout>
<callout arearefs="fixed-address">
<para>Specifies that the host should always be given the
same IP address. Note that using a hostname is
correct here, since the DHCP server will resolve the
hostname itself before returning the lease
information.</para>
</callout>
</calloutlist>
<para>Once the configuration of
<filename>dhcpd.conf</filename> has been completed,
enable the DHCP server in
<filename>/etc/rc.conf</filename>, i.e., by adding:</para>
<programlisting>dhcpd_enable="YES"
dhcpd_ifaces="dc0"</programlisting>
<para>Replace the <literal>dc0</literal> interface name with
the interface (or interfaces, separated by whitespace)
that the DHCP server should listen on for DHCP client
requests.</para>
<para>Proceed to start the server by issuing
the following command:</para>
<screen>&prompt.root; <userinput>service isc-dhcpd start</userinput></screen>
<para>Any future changes to the configuration
of the server will require the sending of a
<literal>SIGTERM</literal> signal to
<application>dhcpd</application> rather than a
<literal>SIGHUP</literal>. It is definitely more
simple to use &man.service.8; to completely restart
the service.</para>
</sect3>
<sect3>
<title>Files</title>
<indexterm>
<primary>DHCP</primary>
<secondary>configuration files</secondary>
</indexterm>
<itemizedlist>
<listitem>
<para><filename>/usr/local/sbin/dhcpd</filename></para>
<para><application>dhcpd</application> is statically
linked and resides in
<filename>/usr/local/sbin</filename>. The
&man.dhcpd.8; manual page installed with the port
gives more information about
<application>dhcpd</application>.</para>
</listitem>
<listitem>
<para><filename>/usr/local/etc/dhcpd.conf</filename></para>
<para><application>dhcpd</application> requires a
configuration file,
<filename>/usr/local/etc/dhcpd.conf</filename> before
it will start providing service to clients. This file
needs to contain all the information that should be
provided to clients that are being serviced, along
with information regarding the operation of the
server. This configuration file is described
by the &man.dhcpd.conf.5; manual page installed
by the port.</para>
</listitem>
<listitem>
<para><filename>/var/db/dhcpd.leases</filename></para>
<para>The DHCP server keeps a database of leases it has
issued in this file, which is written as a log. The
manual page &man.dhcpd.leases.5;, installed by the
port gives a slightly longer description.</para>
</listitem>
<listitem>
<para><filename>/usr/local/sbin/dhcrelay</filename></para>
<para><application>dhcrelay</application> is used in
advanced environments where one DHCP server forwards a
request from a client to another DHCP server on a
separate network. If this functionality is required,
then install the <filename
role="package">net/isc-dhcp42-relay</filename> port.
The &man.dhcrelay.8; manual page provided with the
port contains more detail.</para>
</listitem>
</itemizedlist>
</sect3>
</sect2>
</sect1>
<sect1 id="network-dns">
<sect1info>
<authorgroup>
<author>
<firstname>Chern</firstname>
<surname>Lee</surname>
<contrib>Contributed by </contrib>
</author>
<author>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
</author>
<author>
<firstname>Daniel</firstname>
<surname>Gerzo</surname>
</author>
</authorgroup>
</sect1info>
<title>Domain Name System (<acronym>DNS</acronym>)</title>
<sect2>
<title>Overview</title>
<indexterm><primary>BIND</primary></indexterm>
<para>&os; utilizes, by default, a version of BIND (Berkeley
Internet Name Domain), which is the most common implementation
of the <acronym>DNS</acronym> protocol.
<acronym>DNS</acronym> is the protocol through which names are
mapped to <acronym>IP</acronym> addresses, and vice versa.
For example, a query for <hostid
role="fqdn">www.FreeBSD.org</hostid> will receive a reply
with the <acronym>IP</acronym> address of The &os; Project's
web server, whereas, a query for <hostid
role="fqdn">ftp.FreeBSD.org</hostid> will return the
<acronym>IP</acronym> address of the corresponding
<acronym>FTP</acronym> machine. Likewise, the opposite can
happen. A query for an <acronym>IP</acronym> address can
resolve its hostname. It is not necessary to run a name
server to perform <acronym>DNS</acronym> lookups on a
system.</para>
<para>&os; currently comes with <acronym>BIND</acronym>9
<acronym>DNS</acronym> server software by default. Our
installation provides enhanced security features, a new file
system layout and automated &man.chroot.8;
configuration.</para>
<indexterm><primary>DNS</primary></indexterm>
<para><acronym>DNS</acronym> is coordinated across the Internet
through a somewhat complex system of authoritative root, Top
Level Domain (<acronym>TLD</acronym>), and other smaller-scale
name servers which host and cache individual domain
information.</para>
<para>Currently, BIND is maintained by the
Internet Systems Consortium
<ulink url="https://www.isc.org/"></ulink>.</para>
</sect2>
<sect2>
<title>Terminology</title>
<para>To understand this document, some terms related to
<acronym>DNS</acronym> must be understood.</para>
<indexterm><primary>resolver</primary></indexterm>
<indexterm><primary>reverse DNS</primary></indexterm>
<indexterm><primary>root zone</primary></indexterm>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<colspec colwidth="1*"/>
<colspec colwidth="3*"/>
<thead>
<row>
<entry>Term</entry>
<entry>Definition</entry>
</row>
</thead>
<tbody>
<row>
<entry>Forward <acronym>DNS</acronym></entry>
<entry>Mapping of hostnames to IP addresses.</entry>
</row>
<row>
<entry>Origin</entry>
<entry>Refers to the domain covered in a particular zone
file.</entry>
</row>
<row>
<entry><application>named</application>, BIND</entry>
<entry>Common names for the BIND name server package
within &os;.</entry>
</row>
<row>
<entry>Resolver</entry>
<entry>A system process through which a machine queries
a name server for zone information.</entry>
</row>
<row>
<entry>Reverse <acronym>DNS</acronym></entry>
<entry>Mapping of <acronym>IP</acronym> addresses to
hostnames.</entry>
</row>
<row>
<entry>Root zone</entry>
<entry>The beginning of the Internet zone hierarchy.
All zones fall under the root zone, similar to how
all files in a file system fall under the root
directory.</entry>
</row>
<row>
<entry>Zone</entry>
<entry>An individual domain, subdomain, or portion of
the <acronym>DNS</acronym> administered by the same
authority.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<indexterm>
<primary>zones</primary>
<secondary>examples</secondary>
</indexterm>
<para>Examples of zones:</para>
<itemizedlist>
<listitem>
<para><hostid>.</hostid> is how the root zone is usually
referred to in documentation.</para>
</listitem>
<listitem>
<para><hostid>org.</hostid> is a Top Level Domain
(<acronym>TLD</acronym>) under the root zone.</para>
</listitem>
<listitem>
<para><hostid role="domainname">example.org.</hostid> is a
zone under the <hostid>org.</hostid>
<acronym>TLD</acronym>.</para>
</listitem>
<listitem>
<para><hostid>1.168.192.in-addr.arpa</hostid> is a zone
referencing all <acronym>IP</acronym> addresses which fall
under the <hostid role="ipaddr">192.168.1.*</hostid>
<acronym>IP</acronym> address space.</para>
</listitem>
</itemizedlist>
<para>As one can see, the more specific part of a hostname
appears to its left. For example, <hostid
role="domainname">example.org.</hostid> is more specific
than <hostid>org.</hostid>, as <hostid>org.</hostid> is more
specific than the root zone. The layout of each part of a
hostname is
much like a file system: the
<filename class="directory">/dev</filename> directory falls
within the root, and so on.</para>
</sect2>
<sect2>
<title>Reasons to Run a Name Server</title>
<para>Name servers generally come in two forms: authoritative
name servers, and caching (also known as resolving)
name servers.</para>
<para>An authoritative name server is needed when:</para>
<itemizedlist>
<listitem>
<para>One wants to serve <acronym>DNS</acronym> information
to the world, replying authoritatively to queries.</para>
</listitem>
<listitem>
<para>A domain, such as <hostid
role="domainname">example.org</hostid>, is registered
and <acronym>IP</acronym> addresses need to be assigned
to hostnames under it.</para>
</listitem>
<listitem>
<para>An <acronym>IP</acronym> address block requires
reverse <acronym>DNS</acronym> entries
(<acronym>IP</acronym> to hostname).</para>
</listitem>
<listitem>
<para>A backup or second name server, called a slave, will
reply to queries.</para>
</listitem>
</itemizedlist>
<para>A caching name server is needed when:</para>
<itemizedlist>
<listitem>
<para>A local <acronym>DNS</acronym> server may cache and
respond more quickly than querying an outside name
server.</para>
</listitem>
</itemizedlist>
<para>When one queries for <hostid
role="fqdn">www.FreeBSD.org</hostid>, the resolver usually
queries the uplink <acronym>ISP</acronym>'s name server, and
retrieves the reply. With a local, caching
<acronym>DNS</acronym> server, the query only has to be made
once to the outside world by the caching
<acronym>DNS</acronym> server. Additional queries will not
have to go outside the local network, since the information is
cached
locally.</para>
</sect2>
<sect2>
<title>How It Works</title>
<para>In &os;, the BIND daemon is called
<application>named</application>.</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>File</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>&man.named.8;</entry>
<entry>The BIND daemon.</entry>
</row>
<row>
<entry>&man.rndc.8;</entry>
<entry>Name server control utility.</entry>
</row>
<row>
<entry><filename
class="directory">/etc/namedb</filename></entry>
<entry>Directory where BIND zone information
resides.</entry>
</row>
<row>
<entry><filename>/etc/namedb/named.conf</filename></entry>
<entry>Configuration file of the daemon.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>Depending on how a given zone is configured on the server,
the files related to that zone can be found in the <filename
class="directory">master</filename>, <filename
class="directory">slave</filename>, or <filename
class="directory">dynamic</filename> subdirectories of the
<filename class="directory">/etc/namedb</filename> directory.
These files contain the <acronym>DNS</acronym> information
that will be given out by the name server in response to
queries.</para>
</sect2>
<sect2>
<title>Starting BIND</title>
<indexterm>
<primary>BIND</primary>
<secondary>starting</secondary>
</indexterm>
<para>Since BIND is installed by default, configuring it is
relatively simple.</para>
<para>The default <application>named</application> configuration
is that of a basic resolving name server, running in a
&man.chroot.8; environment, and restricted to listening on
the local IPv4 loopback address (127.0.0.1).
To start the server one time with
this configuration, use the following command:</para>
<screen>&prompt.root; <userinput>service named onestart</userinput></screen>
<para>To ensure the <application>named</application> daemon is
started at boot each time, put the following line into the
<filename>/etc/rc.conf</filename>:</para>
<programlisting>named_enable="YES"</programlisting>
<para>There are obviously many configuration options for
<filename>/etc/namedb/named.conf</filename> that are beyond
the scope of this document. There are other startup options
for <application>named</application> on
&os;, take a look at the
<literal>named_<replaceable>*</replaceable></literal> flags in
<filename>/etc/defaults/rc.conf</filename> and consult the
&man.rc.conf.5; manual page. The <xref
linkend="configtuning-rcd"/> section is also a good
read.</para>
</sect2>
<sect2>
<title>Configuration Files</title>
<indexterm>
<primary>BIND</primary>
<secondary>configuration files</secondary>
</indexterm>
<para>Configuration files for <application>named</application>
currently reside in <filename
class="directory">/etc/namedb</filename> directory and will
need modification before use unless all that is needed is a
simple resolver. This is where most of the configuration will
be performed.</para>
<sect3>
<title><filename>/etc/namedb/named.conf</filename></title>
<programlisting>// &dollar;FreeBSD&dollar;
//
// Refer to the named.conf(5) and named(8) man pages, and the documentation
// in /usr/share/doc/bind9 for more details.
//
// If you are going to set up an authoritative server, make sure you
// understand the hairy details of how DNS works. Even with
// simple mistakes, you can break connectivity for affected parties,
// or cause huge amounts of useless Internet traffic.
options {
// All file and path names are relative to the chroot directory,
// if any, and should be fully qualified.
directory "/etc/namedb/working";
pid-file "/var/run/named/pid";
dump-file "/var/dump/named_dump.db";
statistics-file "/var/stats/named.stats";
// If named is being used only as a local resolver, this is a safe default.
// For named to be accessible to the network, comment this option, specify
// the proper IP address, or delete this option.
listen-on { 127.0.0.1; };
// If you have IPv6 enabled on this system, uncomment this option for
// use as a local resolver. To give access to the network, specify
// an IPv6 address, or the keyword "any".
// listen-on-v6 { ::1; };
// These zones are already covered by the empty zones listed below.
// If you remove the related empty zones below, comment these lines out.
disable-empty-zone "255.255.255.255.IN-ADDR.ARPA";
disable-empty-zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA";
disable-empty-zone "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA";
// If you've got a DNS server around at your upstream provider, enter
// its IP address here, and enable the line below. This will make you
// benefit from its cache, thus reduce overall DNS traffic in the Internet.
/*
forwarders {
127.0.0.1;
};
*/
// If the 'forwarders' clause is not empty the default is to 'forward first'
// which will fall back to sending a query from your local server if the name
// servers in 'forwarders' do not have the answer. Alternatively you can
// force your name server to never initiate queries of its own by enabling the
// following line:
// forward only;
// If you wish to have forwarding configured automatically based on
// the entries in /etc/resolv.conf, uncomment the following line and
// set named_auto_forward=yes in /etc/rc.conf. You can also enable
// named_auto_forward_only (the effect of which is described above).
// include "/etc/namedb/auto_forward.conf";</programlisting>
<para>Just as the comment says, to benefit from an uplink's
cache, <literal>forwarders</literal> can be enabled here.
Under normal circumstances, a name server will recursively
query the Internet looking at certain name servers until it
finds the answer it is looking for. Having this enabled
will have it query the uplink's name server (or name server
provided) first, taking advantage of its cache. If the
uplink name server in question is a heavily trafficked, fast
name server, enabling this may be worthwhile.</para>
<warning>
<para><hostid role="ipaddr">127.0.0.1</hostid> will
<emphasis>not</emphasis> work here. Change this
<acronym>IP</acronym> address to a name server at the
uplink.</para>
</warning>
<programlisting> /*
Modern versions of BIND use a random UDP port for each outgoing
query by default in order to dramatically reduce the possibility
of cache poisoning. All users are strongly encouraged to utilize
this feature, and to configure their firewalls to accommodate it.
AS A LAST RESORT in order to get around a restrictive firewall
policy you can try enabling the option below. Use of this option
will significantly reduce your ability to withstand cache poisoning
attacks, and should be avoided if at all possible.
Replace NNNNN in the example with a number between 49160 and 65530.
*/
// query-source address * port NNNNN;
};
// If you enable a local name server, don't forget to enter 127.0.0.1
// first in your /etc/resolv.conf so this server will be queried.
// Also, make sure to enable it in /etc/rc.conf.
// The traditional root hints mechanism. Use this, OR the slave zones below.
zone "." { type hint; file "/etc/namedb/named.root"; };
/* Slaving the following zones from the root name servers has some
significant advantages:
1. Faster local resolution for your users
2. No spurious traffic will be sent from your network to the roots
3. Greater resilience to any potential root server failure/DDoS
On the other hand, this method requires more monitoring than the
hints file to be sure that an unexpected failure mode has not
incapacitated your server. Name servers that are serving a lot
of clients will benefit more from this approach than individual
hosts. Use with caution.
To use this mechanism, uncomment the entries below, and comment
the hint zone above.
As documented at http://dns.icann.org/services/axfr/ these zones:
"." (the root), ARPA, IN-ADDR.ARPA, IP6.ARPA, and ROOT-SERVERS.NET
are available for AXFR from these servers on IPv4 and IPv6:
xfr.lax.dns.icann.org, xfr.cjr.dns.icann.org
*/
/*
zone "." {
type slave;
file "/etc/namedb/slave/root.slave";
masters {
192.5.5.241; // F.ROOT-SERVERS.NET.
};
notify no;
};
zone "arpa" {
type slave;
file "/etc/namedb/slave/arpa.slave";
masters {
192.5.5.241; // F.ROOT-SERVERS.NET.
};
notify no;
};
*/
/* Serving the following zones locally will prevent any queries
for these zones leaving your network and going to the root
name servers. This has two significant advantages:
1. Faster local resolution for your users
2. No spurious traffic will be sent from your network to the roots
*/
// RFCs 1912 and 5735 (and BCP 32 for localhost)
zone "localhost" { type master; file "/etc/namedb/master/localhost-forward.db"; };
zone "127.in-addr.arpa" { type master; file "/etc/namedb/master/localhost-reverse.db"; };
zone "255.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// RFC 1912-style zone for IPv6 localhost address
zone "0.ip6.arpa" { type master; file "/etc/namedb/master/localhost-reverse.db"; };
// "This" Network (RFCs 1912 and 5735)
zone "0.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Private Use Networks (RFCs 1918 and 5735)
zone "10.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "16.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "17.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "18.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "19.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "20.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "21.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "22.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "23.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "24.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "25.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "26.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "27.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "28.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "29.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "30.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "31.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "168.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Link-local/APIPA (RFCs 3927 and 5735)
zone "254.169.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IETF protocol assignments (RFCs 5735 and 5736)
zone "0.0.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// TEST-NET-[1-3] for Documentation (RFCs 5735 and 5737)
zone "2.0.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "100.51.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "113.0.203.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Range for Documentation (RFC 3849)
zone "8.b.d.0.1.0.0.2.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Domain Names for Documentation and Testing (BCP 32)
zone "test" { type master; file "/etc/namedb/master/empty.db"; };
zone "example" { type master; file "/etc/namedb/master/empty.db"; };
zone "invalid" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.com" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.net" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.org" { type master; file "/etc/namedb/master/empty.db"; };
// Router Benchmark Testing (RFCs 2544 and 5735)
zone "18.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "19.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IANA Reserved - Old Class E Space (RFC 5735)
zone "240.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "241.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "242.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "243.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "244.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "245.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "246.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "247.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "248.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "249.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "250.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "251.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "252.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "253.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "254.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Unassigned Addresses (RFC 4291)
zone "1.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "8.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "c.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "e.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "0.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "1.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "2.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "8.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "0.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "1.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "2.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 ULA (RFC 4193)
zone "c.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Link Local (RFC 4291)
zone "8.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Deprecated Site-Local Addresses (RFC 3879)
zone "c.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "e.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "f.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IP6.INT is Deprecated (RFC 4159)
zone "ip6.int" { type master; file "/etc/namedb/master/empty.db"; };
// NB: Do not use the IP addresses below, they are faked, and only
// serve demonstration/documentation purposes!
//
// Example slave zone config entries. It can be convenient to become
// a slave at least for the zone your own domain is in. Ask
// your network administrator for the IP address of the responsible
// master name server.
//
// Do not forget to include the reverse lookup zone!
// This is named after the first bytes of the IP address, in reverse
// order, with ".IN-ADDR.ARPA" appended, or ".IP6.ARPA" for IPv6.
//
// Before starting to set up a master zone, make sure you fully
// understand how DNS and BIND work. There are sometimes
// non-obvious pitfalls. Setting up a slave zone is usually simpler.
//
// NB: Don't blindly enable the examples below. :-) Use actual names
// and addresses instead.
/* An example dynamic zone
key "exampleorgkey" {
algorithm hmac-md5;
secret "sf87HJqjkqh8ac87a02lla==";
};
zone "example.org" {
type master;
allow-update {
key "exampleorgkey";
};
file "/etc/namedb/dynamic/example.org";
};
*/
/* Example of a slave reverse zone
zone "1.168.192.in-addr.arpa" {
type slave;
file "/etc/namedb/slave/1.168.192.in-addr.arpa";
masters {
192.168.1.1;
};
};
*/</programlisting>
<para>In <filename>named.conf</filename>, these are examples
of slave entries for a forward and reverse zone.</para>
<para>For each new zone served, a new zone entry must be added
to <filename>named.conf</filename>.</para>
<para>For example, the simplest zone entry for
<hostid role="domainname">example.org</hostid> can look
like:</para>
<programlisting>zone "example.org" {
type master;
file "master/example.org";
};</programlisting>
<para>The zone is a master, as indicated by the
<option>type</option> statement, holding its zone
information in
<filename>/etc/namedb/master/example.org</filename>
indicated by the <option>file</option> statement.</para>
<programlisting>zone "example.org" {
type slave;
file "slave/example.org";
};</programlisting>
<para>In the slave case, the zone information is transferred
from the master name server for the particular zone, and
saved in the file specified. If and when the master server
dies or is unreachable, the slave name server will have the
transferred zone information and will be able to serve
it.</para>
</sect3>
<sect3>
<title>Zone Files</title>
<indexterm>
<primary>BIND</primary>
<secondary>zone files</secondary>
</indexterm>
<para>An example master zone file for <hostid
role="domainname">example.org</hostid> (existing within
<filename>/etc/namedb/master/example.org</filename>) is as
follows:</para>
<programlisting>&dollar;TTL 3600 ; 1 hour default TTL
example.org. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh
3600 ; Retry
604800 ; Expire
300 ; Negative Response TTL
)
; DNS Servers
IN NS ns1.example.org.
IN NS ns2.example.org.
; MX Records
IN MX 10 mx.example.org.
IN MX 20 mail.example.org.
IN A 192.168.1.1
; Machine Names
localhost IN A 127.0.0.1
ns1 IN A 192.168.1.2
ns2 IN A 192.168.1.3
mx IN A 192.168.1.4
mail IN A 192.168.1.5
; Aliases
www IN CNAME example.org.</programlisting>
<para>Note that every hostname ending in a <quote>.</quote> is
an exact hostname, whereas everything without a trailing
<quote>.</quote> is relative to the origin. For example,
<literal>ns1</literal> is translated into
<literal>ns1.<replaceable>example.org.</replaceable></literal></para>
<para>The format of a zone file follows:</para>
<programlisting>recordname IN recordtype value</programlisting>
<indexterm>
<primary>DNS</primary>
<secondary>records</secondary>
</indexterm>
<para>The most commonly used DNS records:</para>
<variablelist>
<varlistentry>
<term>SOA</term>
<listitem><para>start of zone authority</para></listitem>
</varlistentry>
<varlistentry>
<term>NS</term>
<listitem>
<para>an authoritative name server</para>
</listitem></varlistentry>
<varlistentry>
<term>A</term>
<listitem><para>a host address</para></listitem>
</varlistentry>
<varlistentry>
<term>CNAME</term>
<listitem><para>the canonical name for an
alias</para></listitem>
</varlistentry>
<varlistentry>
<term>MX</term>
<listitem><para>mail exchanger</para></listitem>
</varlistentry>
<varlistentry>
<term>PTR</term>
<listitem>
<para>a domain name pointer (used in reverse
DNS)</para>
</listitem>
</varlistentry>
</variablelist>
<programlisting>example.org. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh after 3 hours
3600 ; Retry after 1 hour
604800 ; Expire after 1 week
300 ) ; Negative Response TTL</programlisting>
<variablelist>
<varlistentry>
<term><hostid
role="domainname">example.org.</hostid></term>
<listitem>
<para>the domain name, also the origin for this
zone file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><hostid role="fqdn">ns1.example.org.</hostid></term>
<listitem>
<para>the primary/authoritative name server for this
zone.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>admin.example.org.</literal></term>
<listitem>
<para>the responsible person for this zone,
email address with <quote>@</quote>
replaced. (<email>admin@example.org</email> becomes
<literal>admin.example.org</literal>)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>2006051501</literal></term>
<listitem>
<para>the serial number of the file. This
must be incremented each time the zone file is
modified. Nowadays, many admins prefer a
<literal>yyyymmddrr</literal> format for the serial
number. <literal>2006051501</literal> would mean
last modified 05/15/2006, the latter
<literal>01</literal> being the first time the zone
file has been modified this day. The serial number
is important as it alerts slave name servers for a
zone when it is updated.</para>
</listitem>
</varlistentry>
</variablelist>
<programlisting> IN NS ns1.example.org.</programlisting>
<para>This is an NS entry. Every name server that is going to
reply authoritatively for the zone must have one of these
entries.</para>
<programlisting>localhost IN A 127.0.0.1
ns1 IN A 192.168.1.2
ns2 IN A 192.168.1.3
mx IN A 192.168.1.4
mail IN A 192.168.1.5</programlisting>
<para>The A record indicates machine names. As seen above,
<hostid role="fqdn">ns1.example.org</hostid> would resolve
to <hostid role="ipaddr">192.168.1.2</hostid>.</para>
<programlisting> IN A 192.168.1.1</programlisting>
<para>This line assigns IP address <hostid
role="ipaddr">192.168.1.1</hostid> to the current origin,
in this case <hostid
role="domainname">example.org</hostid>.</para>
<programlisting>www IN CNAME @</programlisting>
<para>The canonical name record is usually used for giving
aliases to a machine. In the example, <hostid>www</hostid>
is aliased to the <quote>master</quote> machine whose name
happens to be the same as the domain name <hostid
role="domainname">example.org</hostid> (<hostid
role="ipaddr">192.168.1.1</hostid>). CNAMEs can never be
used together with another kind of record
for the same hostname.</para>
<indexterm>
<primary>MX record</primary>
</indexterm>
<programlisting> IN MX 10 mail.example.org.</programlisting>
<para>The MX record indicates which mail
servers are responsible for handling incoming mail for the
zone. <hostid role="fqdn">mail.example.org</hostid> is the
hostname of a mail server, and 10 is the priority of
that mail server.</para>
<para>One can have several mail servers, with priorities of
10, 20 and so on. A mail server attempting to deliver to
<hostid role="domainname">example.org</hostid> would first
try the highest priority MX (the record with the lowest
priority number), then the second highest, etc, until the
mail can be properly delivered.</para>
<para>For in-addr.arpa zone files (reverse DNS), the same
format is used, except with PTR entries instead of A or
CNAME.</para>
<programlisting>$TTL 3600
1.168.192.in-addr.arpa. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh
3600 ; Retry
604800 ; Expire
300 ) ; Negative Response TTL
IN NS ns1.example.org.
IN NS ns2.example.org.
1 IN PTR example.org.
2 IN PTR ns1.example.org.
3 IN PTR ns2.example.org.
4 IN PTR mx.example.org.
5 IN PTR mail.example.org.</programlisting>
<para>This file gives the proper IP address to hostname
mappings for the above fictitious domain.</para>
<para>It is worth noting that all names on the right side
of a PTR record need to be fully qualified (i.e., end in
a <quote>.</quote>).</para>
</sect3>
</sect2>
<sect2>
<title>Caching Name Server</title>
<indexterm>
<primary>BIND</primary>
<secondary>caching name server</secondary>
</indexterm>
<para>A caching name server is a name server whose primary role
is to resolve recursive queries. It simply asks queries of
its own, and remembers the answers for later use.</para>
</sect2>
<sect2>
<title><acronym
role="Domain Name Security Extensions">DNSSEC</acronym></title>
<indexterm>
<primary>BIND</primary>
<secondary>DNS security extensions</secondary>
</indexterm>
<para>Domain Name System Security Extensions, or <acronym
role="Domain Name Security Extensions">DNSSEC</acronym>
for short, is a suite of specifications to protect resolving
name servers from forged <acronym>DNS</acronym> data, such
as spoofed <acronym>DNS</acronym> records. By using digital
signatures, a resolver can verify the integrity of the
record. Note that <acronym
role="Domain Name Security Extensions">DNSSEC</acronym>
only provides integrity via digitally signing the Resource
Records (<acronym role="Resource Record">RR</acronym>s).
It provides neither confidentiality nor protection against
false end-user assumptions. This means that it cannot
protect against people going to <hostid
role="domainname">example.net</hostid> instead of <hostid
role="domainname">example.com</hostid>. The only thing
<acronym>DNSSEC</acronym> does is authenticate that the data
has not been compromised in transit. The security of
<acronym>DNS</acronym> is an important step in securing the
Internet in general. For more in-depth details of how
<acronym>DNSSEC</acronym> works, the relevant
<acronym>RFC</acronym>s are a good place to start. See the
list in <xref linkend="dns-read"/>.</para>
<para>The following sections will demonstrate how to enable
<acronym>DNSSEC</acronym> for an authoritative
<acronym>DNS</acronym> server and a recursive (or caching)
<acronym>DNS</acronym> server running <acronym>BIND</acronym>
9. While all versions of <acronym>BIND</acronym> 9 support
<acronym>DNSSEC</acronym>, it is necessary to have at least
version 9.6.2 in order to be able to use the signed root zone
when validating <acronym>DNS</acronym> queries. This is
because earlier versions lack the required algorithms to
enable validation using the root zone key. It is strongly
recommended to use the latest version of
<acronym>BIND</acronym> 9.7 or later to take advantage of
automatic key updating for the root key, as well as other
features to automatically keep zones signed and signatures up
to date. Where configurations differ between 9.6.2 and 9.7
and later, differences will be pointed out.</para>
<sect3>
<title>Recursive <acronym>DNS</acronym> Server
Configuration</title>
<para>Enabling <acronym>DNSSEC</acronym> validation of queries
performed by a recursive <acronym>DNS</acronym> server
requires a few changes to <filename>named.conf</filename>.
Before making these changes the root zone key, or trust
anchor, must be acquired. Currently the root zone key is
not available in a file format <acronym>BIND</acronym>
understands, so it has to be manually converted into the
proper format. The key itself can be obtained by querying
the root zone for it using <application>dig</application>.
By running</para>
<screen>&prompt.user; <userinput>dig +multi +noall +answer DNSKEY . &gt; root.dnskey</userinput></screen>
<para>the key will end up in <filename>root.dnskey</filename>.
The contents should look something like this:</para>
<programlisting>. 93910 IN DNSKEY 257 3 8 (
AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQ
bSEW0O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh
/RStIoO8g0NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWA
JQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaDX6RS6CXp
oY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3
LQpzW5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGO
Yl7OyQdXfZ57relSQageu+ipAdTTJ25AsRTAoub8ONGc
LmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1ihz0=
) ; key id = 19036
. 93910 IN DNSKEY 256 3 8 (
AwEAAcaGQEA+OJmOzfzVfoYN249JId7gx+OZMbxy69Hf
UyuGBbRN0+HuTOpBxxBCkNOL+EJB9qJxt+0FEY6ZUVjE
g58sRr4ZQ6Iu6b1xTBKgc193zUARk4mmQ/PPGxn7Cn5V
EGJ/1h6dNaiXuRHwR+7oWh7DnzkIJChcTqlFrXDW3tjt
) ; key id = 34525</programlisting>
<para>Do not be alarmed if the obtained keys differ from this
example. They might have changed since these instructions
were last updated. This output actually contains two keys.
The first key in the listing, with the value 257 after the
DNSKEY record type, is the one needed. This value indicates
that this is a Secure Entry Point (<acronym
role="Secure Entry Point">SEP</acronym>), commonly known
as a Key Signing Key (<acronym
role="Key Signing Key">KSK</acronym>). The second key,
with value 256, is a subordinate key, commonly called a Zone
Signing Key (<acronym
role="Zone Signing Key">ZSK</acronym>). More on the
different key types later in <xref
linkend="dns-dnssec-auth"/>.</para>
<para>Now the key must be verified and formatted so that
<acronym>BIND</acronym> can use it. To verify the key,
generate a <acronym role="Delegation Signer">DS</acronym>
<acronym role="Resource Record">RR</acronym> set. Create a
file containing these <acronym
role="Resource Record">RR</acronym>s with</para>
<screen>&prompt.user; <userinput>dnssec-dsfromkey -f root-dnskey . &gt; root.ds</userinput></screen>
<para>These records use SHA-1 and SHA-256 respectively, and
should look similar to the following example, where the
longer is using SHA-256.</para>
<programlisting>. IN DS 19036 8 1
B256BD09DC8DD59F0E0F0D8541B8328DD986DF6E
. IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5</programlisting>
<para>The SHA-256 <acronym>RR</acronym> can now be compared to
the digest in <ulink
url="https://data.iana.org/root-anchors/root-anchors.xml">https://data.iana.org/root-anchors/root-anchors.xml</ulink>.
To be absolutely sure that the key has not been tampered
with the data in the <acronym>XML</acronym> file can be
verified using the <acronym>PGP</acronym> signature in
<ulink
url="https://data.iana.org/root-anchors/root-anchors.asc">https://data.iana.org/root-anchors/root-anchors.asc</ulink>.</para>
<para>Next, the key must be formatted properly. This differs
a little between <acronym>BIND</acronym> versions 9.6.2 and
9.7 and later. In version 9.7 support was added to
automatically track changes to the key and update it as
necessary. This is done using
<literal>managed-keys</literal> as seen in the example
below. When using the older version, the key is added using
a <literal>trusted-keys</literal> statement and updates must
be done manually. For <acronym>BIND</acronym> 9.6.2 the
format should look like:</para>
<programlisting>trusted-keys {
"." 257 3 8
"AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=";
};</programlisting>
<para>For 9.7 the format will instead be:</para>
<programlisting>managed-keys {
"." initial-key 257 3 8
"AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=";
};</programlisting>
<para>The root key can now be added to
<filename>named.conf</filename> either directly or by
including a file containing the key. After these steps,
configure <acronym>BIND</acronym> to do
<acronym>DNSSEC</acronym> validation on queries by editing
<filename>named.conf</filename> and adding the following to
the <literal>options</literal> directive:</para>
<programlisting>dnssec-enable yes;
dnssec-validation yes;</programlisting>
<para>To verify that it is actually working use
<application>dig</application> to make a query for a signed
zone using the resolver just configured. A successful reply
will contain the <literal>AD</literal> flag to indicate the
data was authenticated. Running a query such as</para>
<screen>&prompt.user; <userinput>dig @<replaceable>resolver</replaceable> +dnssec se ds </userinput></screen>
<para>should return the <acronym>DS</acronym>
<acronym>RR</acronym> for the <literal>.se</literal> zone.
In the <literal>flags:</literal> section the
<literal>AD</literal> flag should be set, as seen
in:</para>
<programlisting>...
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
...</programlisting>
<para>The resolver is now capable of authenticating
<acronym>DNS</acronym> queries.</para>
</sect3>
<sect3 id="dns-dnssec-auth">
<title>Authoritative <acronym>DNS</acronym> Server
Configuration</title>
<para>In order to get an authoritative name server to serve a
<acronym>DNSSEC</acronym> signed zone a little more work is
required. A zone is signed using cryptographic keys which
must be generated. It is possible to use only one key for
this. The preferred method however is to have a strong
well-protected Key Signing Key (<acronym
role="Key Signing Key">KSK</acronym>) that is
not rotated very often and a Zone Signing Key (<acronym
role="Zone Signing Key">ZSK</acronym>) that is rotated more
frequently. Information on recommended operational
practices can be found in <ulink
url="http://tools.ietf.org/rfc/rfc4641.txt"><acronym>RFC</acronym>
4641: <acronym>DNSSEC</acronym> Operational
Practices</ulink>. Practices regarding the root zone can
be found in <ulink
url="http://www.root-dnssec.org/wp-content/uploads/2010/06/icann-dps-00.txt"><acronym>DNSSEC</acronym>
Practice Statement for the Root Zone
<acronym>KSK</acronym> operator</ulink> and <ulink
url="http://www.root-dnssec.org/wp-content/uploads/2010/06/vrsn-dps-00.txt"><acronym>DNSSEC</acronym>
Practice Statement for the Root Zone
<acronym>ZSK</acronym> operator</ulink>. The <acronym
role="Key Signing Key">KSK</acronym> is used to build a
chain of authority to the data in need of validation and as
such is also called a Secure Entry Point (<acronym
role="Secure Entry Point">SEP</acronym>) key. A message
digest of this key, called a Delegation Signer (<acronym
role="Delegation Signer">DS</acronym>) record, must be
published in the parent zone to establish the trust chain.
How this is accomplished depends on the parent zone owner.
The <acronym
role="Zone Signing Key">ZSK</acronym> is used to sign the
zone, and only needs to be published there.</para>
<para>To enable <acronym>DNSSEC</acronym> for the <hostid
role="domainname">example.com</hostid> zone depicted in
previous examples, the first step is to use
<application>dnssec-keygen</application> to generate the
<acronym>KSK</acronym> and <acronym>ZSK</acronym> key pair.
This key pair can utilize different cryptographic
algorithms. It is recommended to use RSA/SHA256 for the
keys and 2048 bits key length should be enough. To generate
the <acronym>KSK</acronym> for <hostid
role="domainname">example.com</hostid>, run</para>
<screen>&prompt.user; <userinput>dnssec-keygen -f KSK -a RSASHA256 -b 2048 -n ZONE example.com</userinput></screen>
<para>and to generate the <acronym>ZSK</acronym>, run</para>
<screen>&prompt.user; <userinput>dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.com</userinput></screen>
<para><application>dnssec-keygen</application> outputs two
files, the public and the private keys in files named
similar to <filename>Kexample.com.+005+nnnnn.key</filename>
(public) and
<filename>Kexample.com.+005+nnnnn.private</filename>
(private). The <literal>nnnnn</literal> part of the file
name is a five digit key ID. Keep track of which key ID
belongs to which key. This is especially important when
having more than one key in a zone. It is
also possible to rename the keys. For each
<acronym>KSK</acronym> file do:</para>
<screen>&prompt.user; <userinput>mv Kexample.com.+005+nnnnn.key Kexample.com.+005+nnnnn.KSK.key</userinput>
&prompt.user; <userinput>mv Kexample.com.+005+nnnnn.private Kexample.com.+005+nnnnn.KSK.private</userinput></screen>
<para>For the <acronym>ZSK</acronym> files, substitute
<literal>KSK</literal> for <literal>ZSK</literal> as
necessary. The files can now be included in the zone file,
using the <literal>$include</literal> statement. It should
look something like this:</para>
<programlisting>$include Kexample.com.+005+nnnnn.KSK.key ; KSK
$include Kexample.com.+005+nnnnn.ZSK.key ; ZSK</programlisting>
<para>Finally, sign the zone and tell <acronym>BIND</acronym>
to use the signed zone file. To sign a zone
<application>dnssec-signzone</application> is used. The
command to sign the zone <hostid
role="domainname">example.com</hostid>, located in
<filename>example.com.db</filename> would look similar
to</para>
<screen>&prompt.user; <userinput>dnssec-signzone -o
example.com -k Kexample.com.+005+nnnnn.KSK example.com.db
Kexample.com.+005+nnnnn.ZSK.key</userinput></screen>
<para>The key supplied to the <option>-k</option> argument is
the <acronym>KSK</acronym> and the other key file is the
<acronym>ZSK</acronym> that should be used in the signing.
It is possible to supply more than one
<acronym>KSK</acronym> and <acronym>ZSK</acronym>, which
will result in the zone being signed with all supplied keys.
This can be needed to supply zone data signed using more
than one algorithm. The output of
<application>dnssec-signzone</application> is a zone file
with all <acronym>RR</acronym>s signed. This output will
end up in a file with the extension
<literal>.signed</literal>, such as
<filename>example.com.db.signed</filename>. The <acronym
role="Delegation Signer">DS</acronym> records will also be
written to a separate file
<filename>dsset-example.com</filename>.
To use this signed zone just modify the zone directive in
<filename>named.conf</filename> to use
<filename>example.com.db.signed</filename>. By default, the
signatures are only valid 30 days, meaning that the zone
needs to be resigned in about 15 days to be sure that
resolvers are not caching records with stale signatures. It
is possible to make a script and a cron job to do this. See
relevant manuals for details.</para>
<para>Be sure to keep private keys confidential, as with all
cryptographic keys. When changing a key it is best to
include the new key into the zone, while still signing with
the old one, and then move over to using the new key to
sign. After these steps are done the old key can be removed
from the zone. Failure to do this might render the
<acronym>DNS</acronym> data unavailable for a time, until
the new key has propagated through the
<acronym>DNS</acronym> hierarchy. For more information on
key rollovers and other <acronym>DNSSEC</acronym>
operational issues, see <ulink
url="http://www.ietf.org/rfc/rfc4641.txt"><acronym>RFC</acronym>
4641: <acronym>DNSSEC</acronym> Operational
practices</ulink>.</para>
</sect3>
<sect3>
<title>Automation Using <acronym>BIND</acronym> 9.7 or
Later</title>
<para>Beginning with <acronym>BIND</acronym> version 9.7 a new
feature called <emphasis>Smart Signing</emphasis> was
introduced. This feature aims to make the key management
and signing process simpler by automating parts of the task.
By putting the keys into a directory called a <emphasis>key
repository</emphasis>, and using the new option
<literal>auto-dnssec</literal>, it is possible to create a
dynamic zone which will be resigned as needed. To update
this zone use <application>nsupdate</application> with the
new option <option>-l</option>.
<application>rndc</application> has also grown the ability
to sign zones with keys in the key repository, using the
option <option>sign</option>. To tell
<acronym>BIND</acronym> to use this automatic signing and
zone updating for <hostid
role="domainname">example.com</hostid>, add the following
to <filename>named.conf</filename>:</para>
<programlisting>zone example.com {
type master;
key-directory "/etc/named/keys";
update-policy local;
auto-dnssec maintain;
file "/etc/named/dynamic/example.com.zone";
};</programlisting>
<para>After making these changes, generate keys for the zone
as explained in <xref linkend="dns-dnssec-auth"/>, put those
keys in the key repository given as the argument to the
<literal>key-directory</literal> in the zone configuration
and the zone will be signed automatically. Updates to a
zone configured this way must be done using
<application>nsupdate</application>, which will take care of
re-signing the zone with the new data added. For further
details, see <xref linkend="dns-read"/> and the
<acronym>BIND</acronym> documentation.</para>
</sect3>
</sect2>
<sect2>
<title>Security</title>
<para>Although BIND is the most common implementation of DNS,
there is always the issue of security. Possible and
exploitable security holes are sometimes found.</para>
<para>While &os; automatically drops
<application>named</application> into a &man.chroot.8;
environment; there are several other security mechanisms in
place which could help to lure off possible
<acronym>DNS</acronym> service attacks.</para>
<para>It is always good idea to read <ulink
url="http://www.cert.org/">CERT</ulink>'s security
advisories and to subscribe to the &a.security-notifications;
to stay up to date with the current Internet and &os; security
issues.</para>
<tip>
<para>If a problem arises, keeping sources up to date and
having a fresh build of <application>named</application>
may help.</para>
</tip>
</sect2>
<sect2 id="dns-read">
<title>Further Reading</title>
<para>BIND/<application>named</application> manual pages:
&man.rndc.8; &man.named.8; &man.named.conf.5; &man.nsupdate.1;
&man.dnssec-signzone.8; &man.dnssec-keygen.8;</para>
<itemizedlist>
<listitem>
<para><ulink
url="https://www.isc.org/software/bind">Official ISC
BIND Page</ulink></para>
</listitem>
<listitem>
<para><ulink
url="https://www.isc.org/software/guild">Official ISC
BIND Forum</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://www.oreilly.com/catalog/dns5/">O'Reilly
DNS and BIND 5th Edition</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://www.root-dnssec.org/documentation/">Root
<acronym>DNSSEC</acronym></ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://data.iana.org/root-anchors/draft-icann-dnssec-trust-anchor.html"><acronym>DNSSEC</acronym>
Trust Anchor Publication for the Root
Zone</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc1034">RFC1034
- Domain Names - Concepts and Facilities</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc1035">RFC1035
- Domain Names - Implementation and
Specification</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc4033">RFC4033
- DNS Security Introduction and
Requirements</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc4034">RFC4034
- Resource Records for the DNS Security
Extensions</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc4035">RFC4035
- Protocol Modifications for the DNS Security
Extensions</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc4641">RFC4641
- DNSSEC Operational Practices</ulink></para>
</listitem>
<listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc5011">RFC 5011
- Automated Updates of DNS Security
(<acronym>DNSSEC</acronym>
Trust Anchors</ulink></para>
</listitem>
</itemizedlist>
</sect2>
</sect1>
<sect1 id="network-apache">
<sect1info>
<authorgroup>
<author>
<firstname>Murray</firstname>
<surname>Stokely</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
<title>Apache HTTP Server</title>
<indexterm><primary>web servers</primary>
<secondary>setting up</secondary></indexterm>
<indexterm><primary>Apache</primary></indexterm>
<sect2>
<title>Overview</title>
<para>&os; is used to run some of the busiest web sites in the
world. The majority of web servers on the Internet are using
the <application>Apache HTTP Server</application>.
<application>Apache</application> software packages should be
included on the &os; installation media. If
<application>Apache</application> was not installed while
installing &os;, then it can be installed from the <filename
role="package">www/apache22</filename> port.</para>
<para>Once <application>Apache</application> has been installed
successfully, it must be configured.</para>
<note><para>This section covers version 2.2.X of the
<application>Apache HTTP Server</application> as that is the
most widely used version for &os;. For more detailed
information beyond the scope of this document about
<application>Apache</application>&nbsp;2.X, please see <ulink
url="http://httpd.apache.org/"></ulink>.</para></note>
</sect2>
<sect2>
<title>Configuration</title>
<indexterm><primary>Apache</primary>
<secondary>configuration file</secondary></indexterm>
<para>The main <application>Apache HTTP Server</application>
configuration file is installed as
<filename>/usr/local/etc/apache22/httpd.conf</filename> on
&os;. This file is a typical &unix; text configuration file
with comment lines beginning with the <literal>#</literal>
character. A comprehensive description of all possible
configuration options is outside the scope of this book, so
only the most frequently modified directives will be described
here.</para>
<variablelist>
<varlistentry>
<term><literal>ServerRoot "/usr/local"</literal></term>
<listitem>
<para>This specifies the default directory hierarchy for
the <application>Apache</application> installation.
Binaries are stored in the <filename
class="directory">bin</filename> and
<filename
class="directory">sbin</filename> subdirectories
of the server root, and configuration files are stored
in <filename
class="directory">etc/apache</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ServerAdmin you@your.address</literal></term>
<listitem>
<para>The address to which problems with the server should
be emailed. This address also appears on some
server-generated pages, such as error documents.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ServerName www.example.com</literal></term>
<listitem>
<para><literal>ServerName</literal> allows an administrator
to set a host name which is sent back to clients for the
server. This is useful if the host is different than the
one that it is configured with (i.e., use
<hostid>www</hostid> instead
of the host's real name).</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DocumentRoot
"/usr/local/www/apache22/data"</literal></term>
<listitem>
<para><literal>DocumentRoot</literal>: The directory
where documents will be served from. By default, all
requests are taken from this directory, but symbolic
links and aliases may be used to point to other
locations.</para>
</listitem>
</varlistentry>
</variablelist>
<para>It is always a good idea to make backup copies of the
<application>Apache</application> configuration file before
making changes. When the configuration of
<application>Apache</application>, is complete, save the
file and verify the configuration using &man.apachectl.8;.
To do this, issue <command>apachectl configtest</command>
which should return <literal>Syntax OK</literal>.</para>
</sect2>
<sect2>
<title>Running <application>Apache</application></title>
<indexterm><primary>Apache</primary>
<secondary>starting or stopping</secondary></indexterm>
<para>The <filename role="package">www/apache22</filename> port
installs an &man.rc.8; script to aid in starting, stopping,
and restarting <application>Apache</application>, which can be
found in <filename
class="directory">/usr/local/etc/rc.d/</filename>.</para>
<para>To launch <application>Apache</application> at system
startup, add the following line to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>apache22_enable="YES"</programlisting>
<para>If <application>Apache</application> should be started
with non-default options, the following line may be added to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>apache22_flags=""</programlisting>
<para>The <application>Apache</application> configuration can be
tested for errors after making subsequent
configuration changes while <command>httpd</command> is
running. This can be done by the &man.rc.8; script directly,
or by the &man.service.8; utility by issuing one of the
following commands:</para>
<screen>&prompt.root; <userinput>service apache22 configtest</userinput></screen>
<note>
<para>It is important to note that the
<literal>configtest</literal> is not an &man.rc.8; standard,
and should not be expected to work for all &man.rc.8;
startup scripts.</para>
</note>
<para>If <application>Apache</application> does not report
configuration errors, the
<application>Apache</application>&nbsp;<command>httpd</command>
can be started with &man.service.8;:</para>
<screen>&prompt.root; <userinput>service apache22 start</userinput></screen>
<para>The <command>httpd</command> service can be tested by
entering <literal>http://<hostid
role="fqdn"><replaceable>localhost</replaceable></hostid></literal>
in a web browser, replacing
<replaceable>localhost</replaceable> with the fully-qualified
domain name of the machine running <command>httpd</command>,
if it is not the local machine. The default web page that is
displayed is
<filename>/usr/local/www/apache22/data/index.html</filename>.</para>
</sect2>
<sect2>
<title>Virtual Hosting</title>
<para><application>Apache</application> supports two different
types of Virtual Hosting. The first method is Name-based
Virtual Hosting. Name-based virtual hosting uses the clients
HTTP/1.1 headers to figure out the hostname. This allows many
different domains to share the same IP address.</para>
<para>To setup <application>Apache</application> to use
Name-based Virtual Hosting add an entry like the following to
<filename>httpd.conf</filename>:</para>
<programlisting>NameVirtualHost *</programlisting>
<para>If the webserver was named <hostid
role="fqdn">www.domain.tld</hostid> and
a virtual domain for <hostid
role="fqdn">www.someotherdomain.tld</hostid> then
add the following entries to
<filename>httpd.conf</filename>:</para>
<screen>&lt;VirtualHost *&gt;
ServerName www.domain.tld
DocumentRoot /www/domain.tld
&lt;/VirtualHost&gt;
&lt;VirtualHost *&gt;
ServerName www.someotherdomain.tld
DocumentRoot /www/someotherdomain.tld
&lt;/VirtualHost&gt;</screen>
<para>Replace the addresses with the addresses needed
and the path to the documents with what are being used.</para>
<para>For more information about setting up virtual hosts,
please consult the official <application>Apache</application>
documentation at: <ulink
url="http://httpd.apache.org/docs/vhosts/"></ulink>.</para>
</sect2>
<sect2>
<title>Apache Modules</title>
<indexterm><primary>Apache</primary>
<secondary>modules</secondary></indexterm>
<para>There are many different <application>Apache</application>
modules available to add functionality to the basic server.
The FreeBSD Ports Collection provides an easy way to install
<application>Apache</application> together with some of the
more popular add-on modules.</para>
<sect3>
<title><application>mod_ssl</application></title>
<indexterm><primary>web servers</primary>
<secondary>secure</secondary></indexterm>
<indexterm><primary>SSL</primary></indexterm>
<indexterm><primary>cryptography</primary></indexterm>
<para>The <application>mod_ssl</application> module uses the
OpenSSL library to provide strong cryptography via the
Secure Sockets Layer (SSL v2/v3) and Transport Layer
Security (TLS v1) protocols. This module provides
everything necessary to request a signed certificate from
a trusted certificate signing authority to run
a secure web server on &os;.</para>
<para>The <application>mod_ssl</application> module is built
by default, but can be enabled by specifying
<literal>-DWITH_SSL</literal> at compile time.</para>
</sect3>
<sect3>
<title>Language Bindings</title>
<para>There are Apache modules for most major scripting
languages. These modules typically make it possible to
write <application>Apache</application> modules entirely in
a scripting language. They are also often used as a
persistent interpreter embedded into the server that avoids
the overhead of starting an external interpreter and the
startup-time penalty for dynamic websites, as described in
the next section.</para>
</sect3>
</sect2>
<sect2>
<title>Dynamic Websites</title>
<indexterm><primary>web servers</primary>
<secondary>dynamic</secondary></indexterm>
<para>In the last decade, more businesses have turned to the
Internet in order to enhance their revenue and increase
exposure. This has also increased the need for interactive
web content. While some companies, such as &microsoft;,
have introduced solutions into their proprietary products,
the open source community answered the call. Modern options
for dynamic web content include Django, Ruby on Rails,
<application>mod_perl2</application>, and
<application>mod_php</application>.</para>
<sect3>
<title>Django</title>
<indexterm><primary>Python</primary></indexterm>
<indexterm><primary>Django</primary></indexterm>
<para>Django is a BSD licensed framework designed to allow
developers to write high performance, elegant web
applications quickly. It provides an object-relational
mapper so that data types are developed as Python objects,
and a rich dynamic database-access API is provided for those
objects without the developer ever having to write SQL. It
also provides an extensible template system so that the
logic of the application is separated from the HTML
presentation.</para>
<para>Django depends on <application>mod_python</application>,
<application>Apache</application>, and an SQL database
engine. The &os; Port will install all of
these pre-requisites with the appropriate
flags.</para>
<example id="network-www-django-install">
<title>Installing Django with
<application>Apache2</application>,
<application>mod_python3</application>, and
<application>PostgreSQL</application></title>
<screen>&prompt.root; <userinput>cd /usr/ports/www/py-django; make all install clean -DWITH_MOD_PYTHON3 -DWITH_POSTGRESQL</userinput></screen>
</example>
<para>Once Django and these pre-requisites are installed,
the application will need a Django project directory along
with the Apache configuration to use the embedded Python
interpreter. This will be the interpreter to
call the application for specific URLs on the site.</para>
<example id="network-www-django-apache-config">
<title>Apache Configuration for Django/mod_python</title>
<para>A line must be added to the apache
<filename>httpd.conf</filename> file to configure Apache
to pass requests for certain URLs to the web
application:</para>
<screen>&lt;Location "/"&gt;
SetHandler python-program
PythonPath "['/dir/to/the/django/packages/'] + sys.path"
PythonHandler django.core.handlers.modpython
SetEnv DJANGO_SETTINGS_MODULE mysite.settings
PythonAutoReload On
PythonDebug On
&lt;/Location&gt;</screen>
</example>
</sect3>
<sect3>
<title>Ruby on Rails</title>
<indexterm><primary>Ruby on Rails</primary></indexterm>
<para>Ruby on Rails is another open source web framework that
provides a full development stack and is optimized to make
web developers more productive and capable of writing
powerful applications quickly. It can be installed easily
from the ports system.</para>
<screen>&prompt.root; <userinput>cd /usr/ports/www/rubygem-rails; make all install clean</userinput></screen>
</sect3>
<sect3>
<title><application>mod_perl2</application></title>
<indexterm>
<primary>mod_perl2</primary>
<secondary>Perl</secondary>
</indexterm>
<para>The <application>Apache</application>/Perl integration
project brings together the full power of the Perl
programming language and the
<application>Apache HTTP Server</application>. With the
<application>mod_perl2</application> module it is possible
to write <application>Apache</application> modules entirely
in Perl. In addition, the persistent interpreter embedded
in the server avoids the overhead of starting an external
interpreter and the penalty of Perl start-up time.</para>
<para><application>mod_perl2</application> is available in the
<filename role="package">www/mod_perl2</filename>
port.</para>
</sect3>
<sect3>
<sect3info>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</sect3info>
<title><application>mod_php</application></title>
<indexterm>
<primary>mod_php</primary>
<secondary>PHP</secondary>
</indexterm>
<para><acronym>PHP</acronym>, also known as <quote>PHP:
Hypertext Preprocessor</quote> is a general-purpose
scripting language that is especially suited for Web
development. Capable of being embedded into
<acronym>HTML</acronym> its syntax draws upon C, &java;,
and Perl with the intention of allowing web developers to
write dynamically generated webpages quickly.</para>
<para>To gain support for <acronym>PHP</acronym>5 for the
<application>Apache</application> web server, begin by
installing the
<filename role="package">lang/php5</filename>
port.</para>
<para>If the <filename role="package">lang/php5</filename>
port is being installed for the first time, available
<literal>OPTIONS</literal> will be displayed automatically.
If a menu is not displayed, i.e., because the <filename
role="package">lang/php5</filename> port has been installed
some time in the past, it is always possible to bring the
options dialog up again by running:</para>
<screen>&prompt.root; <userinput>make config</userinput></screen>
<para>in the port directory.</para>
<para>In the options dialog, check the
<literal>APACHE</literal> option to build
<application>mod_php5</application> as a loadable module for
the <application>Apache</application> web server.</para>
<note>
<para>A lot of sites are still using <acronym>PHP</acronym>4
for various reasons (i.e., compatibility issues or already
deployed web applications). If the
<application>mod_php4</application> is needed instead of
<application>mod_php5</application>, then please use the
<filename role="package">lang/php4</filename> port. The
<filename role="package">lang/php4</filename> port
supports many of the configuration and build-time options
of the <filename role="package">lang/php5</filename>
port.</para>
</note>
<para>This will install and configure the modules required
to support dynamic <acronym>PHP</acronym> applications.
Check to ensure the following sections have been added to
<filename>/usr/local/etc/apache22/httpd.conf</filename>:</para>
<programlisting>LoadModule php5_module libexec/apache/libphp5.so</programlisting>
<programlisting>AddModule mod_php5.c
&lt;IfModule mod_php5.c&gt;
DirectoryIndex index.php index.html
&lt;/IfModule&gt;
&lt;IfModule mod_php5.c&gt;
AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
&lt;/IfModule&gt;</programlisting>
<para>Once completed, a simple call to the
<command>apachectl</command> command for a graceful
restart is needed to load the <acronym>PHP</acronym>
module:</para>
<screen>&prompt.root; <userinput>apachectl graceful</userinput></screen>
<para>For future upgrades of <acronym>PHP</acronym>, the
<command>make config</command> command will not be required;
the selected <literal>OPTIONS</literal> are saved
automatically by the &os; Ports framework.</para>
<para>The <acronym>PHP</acronym> support in &os; is extremely
modular so the base install is very limited. It is very
easy to add support using the <filename
role="package">lang/php5-extensions</filename> port.
This port provides a menu driven interface to
<acronym>PHP</acronym> extension installation.
Alternatively, individual extensions can be installed using
the appropriate port.</para>
<para>For instance, to add support for the
<application>MySQL</application> database server to
<acronym>PHP</acronym>5, simply install the port
<filename>databases/php5-mysql</filename>.</para>
<para>After installing an extension, the
<application>Apache</application> server must be reloaded to
pick up the new configuration changes:</para>
<screen>&prompt.root; <userinput>apachectl graceful</userinput></screen>
</sect3>
</sect2>
</sect1>
<sect1 id="network-ftp">
<sect1info>
<authorgroup>
<author>
<firstname>Murray</firstname>
<surname>Stokely</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
<title>File Transfer Protocol (FTP)</title>
<indexterm><primary>FTP servers</primary></indexterm>
<sect2>
<title>Overview</title>
<para>The File Transfer Protocol (FTP) provides users with a
simple way to transfer files to and from an <acronym
role="File Transfer Protocol">FTP</acronym> server. &os;
includes <acronym role="File Transfer Protocol">FTP</acronym>
server software, <application>ftpd</application>, in the base
system. This makes setting up and administering an <acronym
role="File Transfer Protocol">FTP</acronym> server on FreeBSD
very straightforward.</para>
</sect2>
<sect2>
<title>Configuration</title>
<para>The most important configuration step is deciding which
accounts will be allowed access to the FTP server. A normal
&os; system has a number of system accounts used for
various daemons, but unknown users should not be allowed to
log in with these accounts. The
<filename>/etc/ftpusers</filename> file is a list of users
disallowed any FTP access. By default, it includes the
aforementioned system accounts, but it is possible to add
specific users here that should not be allowed access to
FTP.</para>
<para>In some cases it may be desirable to restrict the access
of some users without
preventing them completely from using FTP. This can be
accomplished with the <filename>/etc/ftpchroot</filename>
file. This file lists users and groups subject to FTP access
restrictions. The &man.ftpchroot.5; manual page has all of
the details so it will not be described in detail here.</para>
<indexterm>
<primary>FTP</primary>
<secondary>anonymous</secondary>
</indexterm>
<para>To enable anonymous FTP access to the
server, create a user named
<username>ftp</username> on the &os; system. Users will then
be able to log on to the FTP server with a username of
<username>ftp</username> or <username>anonymous</username> and
with any password (by convention an email address for the user
should be used as the password). The FTP server will call
&man.chroot.2; when an anonymous user logs in, to restrict
access to only the home directory of the
<username>ftp</username> user.</para>
<para>There are two text files that specify welcome messages to
be displayed to FTP clients. The contents of the file
<filename>/etc/ftpwelcome</filename> will be displayed to
users before they reach the login prompt. After a successful
login, the contents of the file
<filename>/etc/ftpmotd</filename> will be displayed. Note
that the path to this file is relative to the login
environment, so the file <filename>~ftp/etc/ftpmotd</filename>
would be displayed for anonymous users.</para>
<para>Once the FTP server has been configured properly, it must
be enabled in <filename>/etc/inetd.conf</filename>. All that
is required here is to remove the comment symbol
<quote>#</quote> from in front of the existing
<application>ftpd</application> line :</para>
<programlisting>ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l</programlisting>
<para>As explained in <xref linkend="network-inetd-reread"/>,
the <application>inetd</application> configuration must be
reloaded after this configuration file is changed. Please
refer to <xref linkend="network-inetd-settings"/> for details
on enabling <application>inetd</application> on the
system.</para>
<para>Alternatively, <application>ftpd</application> can also be
started as a stand-alone server. In this case, it is
sufficient to set the appropriate variable in
<filename>/etc/rc.conf</filename>:</para>
<programlisting>ftpd_enable="YES"</programlisting>
<para>After setting the above variable, the stand-alone server
will be started at the next reboot, or it can be started
manually by executing the following command as
<username>root</username>:</para>
<screen>&prompt.root; <userinput>service ftpd start</userinput></screen>
<para>You can now log on to the FTP server by typing:</para>
<screen>&prompt.user; <userinput>ftp localhost</userinput></screen>
</sect2>
<sect2>
<title>Maintaining</title>
<indexterm><primary>syslog</primary></indexterm>
<indexterm><primary>log files</primary>
<secondary>FTP</secondary></indexterm>
<para>The <application>ftpd</application> daemon uses
&man.syslog.3; to log messages. By default, the system log
daemon will put messages related to FTP in the
<filename>/var/log/xferlog</filename> file. The location of
the FTP log can be modified by changing the following line in
<filename>/etc/syslog.conf</filename>:</para>
<programlisting>ftp.info /var/log/xferlog</programlisting>
<indexterm>
<primary>FTP</primary>
<secondary>anonymous</secondary>
</indexterm>
<para>Be aware of the potential problems involved with running
an anonymous FTP server. In particular, think
twice about allowing anonymous users to upload files. It may
turn out that the FTP site becomes a forum for the trade of
unlicensed commercial software or worse. If anonymous
FTP uploads are required, then verify the
permissions so that these files can not be read by other
anonymous users until they have been reviewed by an
administrator.</para>
</sect2>
</sect1>
<sect1 id="network-samba">
<sect1info>
<authorgroup>
<author>
<firstname>Murray</firstname>
<surname>Stokely</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
<title>File and Print Services for &microsoft.windows; Clients
(Samba)</title>
<indexterm><primary>Samba server</primary></indexterm>
<indexterm><primary>Microsoft Windows</primary></indexterm>
<indexterm>
<primary>file server</primary>
<secondary>Windows clients</secondary>
</indexterm>
<indexterm>
<primary>print server</primary>
<secondary>Windows clients</secondary>
</indexterm>
<sect2>
<title>Overview</title>
<para><application>Samba</application> is a popular open source
software package that provides file and print services for
&microsoft.windows; clients. Such clients can connect to and
use &os; filespace as if it was a local disk drive, or
&os; printers as if they were local printers.</para>
<para><application>Samba</application> software packages should
be included on the &os; installation media. If they were
not installed when first
installing &os;, then they may be installed from the <filename
role="package">net/samba34</filename> port or package.</para>
<!-- mention LDAP, Active Directory, WinBIND, ACL, Quotas, PAM, .. -->
</sect2>
<sect2>
<title>Configuration</title>
<para>A default <application>Samba</application> configuration
file is installed as
<filename>/usr/local/share/examples/samba34/smb.conf.default</filename>.
This file must be copied to
<filename>/usr/local/etc/smb.conf</filename> and customized
before <application>Samba</application> can be used.</para>
<para>The <filename>smb.conf</filename> file contains runtime
configuration information for
<application>Samba</application>, such as definitions of the
printers and <quote>file system shares</quote> that will
be shared with &windows; clients. The
<application>Samba</application> package includes a web based
tool called <application>swat</application> which provides a
simple way of configuring the <filename>smb.conf</filename>
file.</para>
<sect3>
<title>Using the Samba Web Administration Tool (SWAT)</title>
<para>The Samba Web Administration Tool (SWAT) runs as a
daemon from <application>inetd</application>. Therefore,
<application>inetd</application> must be enabled as shown in
<xref linkend="network-inetd"/>, and
the following line in <filename>/etc/inetd.conf</filename>
should be uncommented before <application>swat</application>
can be used to configure
<application>Samba</application>:</para>
<programlisting>swat stream tcp nowait/400 root /usr/local/sbin/swat swat</programlisting>
<para>As explained in <xref linkend="network-inetd-reread"/>,
the <application>inetd</application> configuration must be
reloaded after this configuration file is changed.</para>
<para>Once <application>swat</application> has been enabled in
<filename>inetd.conf</filename>, a web browser may be used to
connect to <ulink url="http://localhost:901"></ulink>. At
first login, the system
<username>root</username> account must be used.</para>
<!-- XXX screenshots go here, loader is creating them
XXXTR: I'll believe it when I see it. -->
<para>Once successfully logging on to the main
<application>Samba</application> configuration page, the
system documentation will be available, or configuration may
begin by clicking on the
<guimenu>Globals</guimenu> tab. The
<guimenu>Globals</guimenu> section corresponds to the
variables that are set in the <literal>[global]</literal>
section of
<filename>/usr/local/etc/smb.conf</filename>.</para>
</sect3>
<sect3>
<title>Global Settings</title>
<para>Whether <application>swat</application> is being used or
<filename>/usr/local/etc/smb.conf</filename> is being edited
directly, the first directives encountered
when configuring <application>Samba</application>
are:</para>
<variablelist>
<varlistentry>
<term><literal>workgroup</literal></term>
<listitem>
<para>NT Domain-Name or Workgroup-Name for the computers
that will be accessing this server.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>netbios name</literal></term>
<listitem>
<para>This sets the NetBIOS name by which a
<application>Samba</application> server is known.
By default it is the same as the first component of
the host's DNS name.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>server string</literal></term>
<listitem>
<para>This sets the string that will be displayed with
the <command>net view</command> command and some other
networking tools that seek to display descriptive text
about the server.</para>
</listitem>
</varlistentry>
</variablelist>
</sect3>
<sect3>
<title>Security Settings</title>
<para>Two of the most important settings in
<filename>/usr/local/etc/smb.conf</filename> are the
security model chosen, and the backend password format for
client users. The following directives control these
options:</para>
<variablelist>
<varlistentry>
<term><literal>security</literal></term>
<listitem>
<para>The two most common options here are
<literal>security = share</literal> and
<literal>security = user</literal>. If the clients
use usernames that are the same as their usernames on
the &os; machine then user level security should be
used. This is the default security policy and it
requires clients to first log on before they can
access shared resources.</para>
<para>In share level security, clients do not need to log
onto the server with a valid username and password
before attempting to connect to a shared resource.
This was the default security model for older versions
of <application>Samba</application>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>passdb backend</literal></term>
<listitem>
<indexterm><primary>NIS+</primary></indexterm>
<indexterm><primary>LDAP</primary></indexterm>
<indexterm><primary>SQL database</primary></indexterm>
<para><application>Samba</application> has several
different backend authentication models. Clients may
be authenticated with LDAP, NIS+, an SQL database,
or a modified password file. The default
authentication method is <literal>smbpasswd</literal>,
and that is all that will be covered here.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Assuming that the default <literal>smbpasswd</literal>
backend is used, the
<filename>/usr/local/etc/samba/smbpasswd</filename> file
must be created to allow <application>Samba</application> to
authenticate clients. To provide
the &unix; user accounts access from &windows; clients, use
the following command:</para>
<screen>&prompt.root; <userinput>smbpasswd -a username</userinput></screen>
<note>
<para>The recommended backend is now
<literal>tdbsam</literal>, and the following command
should be used to add user accounts:</para>
<screen>&prompt.root; <userinput><command>pdbedit <option>-a</option> <option>-u</option> <replaceable>username</replaceable></command></userinput></screen>
</note>
<para>Please see the
<ulink
url="http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/">Official
Samba HOWTO</ulink>
for additional information about configuration
options. With the basics outlined here, the minimal required
start running <application>Samba</application> will
be explained. Other documentation should be consulted in
addition to the information here.</para>
</sect3>
</sect2>
<sect2>
<title>Starting <application>Samba</application></title>
<para>The <filename role="package">net/samba34</filename> port
adds a new startup script, which can be used to control
<application>Samba</application>. To enable this script, so
that it can be used for example to start, stop or restart
<application>Samba</application>, add the following line to
the <filename>/etc/rc.conf</filename> file:</para>
<programlisting>samba_enable="YES"</programlisting>
<para>Or, for fine grain control:</para>
<programlisting>nmbd_enable="YES"</programlisting>
<programlisting>smbd_enable="YES"</programlisting>
<note>
<para>This will also configure
<application>Samba</application> to automatically start at
system boot time.</para>
</note>
<para>It is possible then to start
<application>Samba</application> at any time by typing:</para>
<screen>&prompt.root; <userinput>service samba start</userinput>
Starting SAMBA: removing stale tdbs :
Starting nmbd.
Starting smbd.</screen>
<para>Please refer to <xref linkend="configtuning-rcd"/> for
more information about using rc scripts.</para>
<para><application>Samba</application> actually consists of
three separate daemons. Notice that both the
<application>nmbd</application> and
<application>smbd</application> daemons are started by the
<filename>samba</filename> script. If winbind,
name resolution services were enabled in
<filename>smb.conf</filename>,
the <application>winbindd</application> daemon will be
started as well.</para>
<para><application>Samba</application> may be stopped at any time
by typing:</para>
<screen>&prompt.root; <userinput>service samba stop</userinput></screen>
<para><application>Samba</application> is a complex software
suite with functionality that allows broad integration with
&microsoft.windows; networks. For more information about
functionality beyond the basic installation described here,
please see <ulink url="http://www.samba.org"></ulink>.</para>
</sect2>
</sect1>
<sect1 id="network-ntp">
<sect1info>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Hukins</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
<title>Clock Synchronization with NTP</title>
<indexterm><primary>NTP</primary></indexterm>
<sect2>
<title>Overview</title>
<para>Over time, a computer's clock is prone to drift. The
Network Time Protocol (NTP) is one way to ensure the clock
stays accurate.</para>
<para>Many Internet services rely on, or greatly benefit from,
computers' clocks being accurate. For example, a web server
may receive requests to send a file if it has been modified
since a certain time. In a local area network environment, it
is essential that computers sharing files from the same file
server have synchronized clocks so that file timestamps stay
consistent. Services such as &man.cron.8; also rely on
an accurate system clock to run commands at the specified
times.</para>
<indexterm>
<primary>NTP</primary>
<secondary>ntpd</secondary>
</indexterm>
<para>&os; ships with the &man.ntpd.8; <acronym
role="Network Time Protocol">NTP</acronym> server which can
be used to query other <acronym
role="Network Time Protocol">NTP</acronym> servers to set
the clock on the machine or provide time
services to others.</para>
</sect2>
<sect2>
<title>Choosing Appropriate NTP Servers</title>
<indexterm>
<primary>NTP</primary>
<secondary>choosing servers</secondary>
</indexterm>
<para>In order to synchronize the clock, one or more
<acronym role="Network Time Protocol">NTP</acronym> servers
must be defined. The network
administrator or ISP may have set up an NTP server for this
purpose&mdash;check their documentation to see if this is the
case. There is an <ulink
url="http://support.ntp.org/bin/view/Servers/WebHome">online
list of publicly accessible NTP servers</ulink> which may be
referenced to find an NTP server nearest to the system.
Take care to review the policy for any chosen servers, and ask
for permission if required.</para>
<para>Choosing several unconnected NTP servers is a good idea in
case one of the servers being used becomes unreachable or
its clock is unreliable. &man.ntpd.8; uses the responses it
receives from other servers intelligently&mdash;it will favor
unreliable servers less than reliable ones.</para>
</sect2>
<sect2>
<title>Configuring The Machine</title>
<indexterm>
<primary>NTP</primary>
<secondary>configuration</secondary>
</indexterm>
<sect3>
<title>Basic Configuration</title>
<indexterm><primary>ntpdate</primary></indexterm>
<para>To synchronize the clock only when the
machine boots up, use &man.ntpdate.8;. This may be
appropriate for some desktop machines which are frequently
rebooted and only require infrequent synchronization, but
most machines should run &man.ntpd.8;.</para>
<para>Using &man.ntpdate.8; at boot time is also a good idea
for machines that run &man.ntpd.8;. The &man.ntpd.8;
program changes the clock gradually, whereas &man.ntpdate.8;
sets the clock, no matter how great the difference between a
machine's current clock setting and the correct time.</para>
<para>To enable &man.ntpdate.8; at boot time, add
<literal>ntpdate_enable="YES"</literal> to
<filename>/etc/rc.conf</filename>. Also
specify all synchronization servers and any
flags to be passed to &man.ntpdate.8; in
<varname>ntpdate_flags</varname>.</para>
</sect3>
<sect3>
<title>General Configuration</title>
<indexterm>
<primary>NTP</primary>
<secondary>ntp.conf</secondary>
</indexterm>
<para>NTP is configured by the
<filename>/etc/ntp.conf</filename> file in the format
described in &man.ntp.conf.5;. Here is a simple
example:</para>
<programlisting>server ntplocal.example.com prefer
server timeserver.example.org
server ntp2a.example.net
driftfile /var/db/ntp.drift</programlisting>
<para>The <literal>server</literal> option specifies which
servers are to be used, with one server listed on each line.
If a server is specified with the <literal>prefer</literal>
argument, as with <hostid
role="fqdn">ntplocal.example.com</hostid>, that server is
preferred over other servers. A response from a preferred
server will be discarded if it differs significantly from
other servers' responses, otherwise it will be used without
any consideration to other responses. The
<literal>prefer</literal> argument is normally used for NTP
servers that are known to be highly accurate, such as those
with special time monitoring hardware.</para>
<para>The <literal>driftfile</literal> option specifies which
file is used to store the system clock's frequency offset.
The &man.ntpd.8; program uses this to automatically
compensate for the clock's natural drift, allowing it to
maintain a reasonably correct setting even if it is cut off
from all external time sources for a period of time.</para>
<para>The <literal>driftfile</literal> option specifies which
file is used to store information about previous responses
from the NTP servers being used. This file contains
internal information for NTP. It should not be modified by
any other process.</para>
</sect3>
<sect3>
<title>Controlling Access to Your Server</title>
<para>By default, the NTP server will be accessible to all
hosts on the Internet. The <literal>restrict</literal>
option in <filename>/etc/ntp.conf</filename>
controls which machines can access the server.</para>
<para>To deny all machines from accessing the NTP
server, add the following line to
<filename>/etc/ntp.conf</filename>:</para>
<programlisting>restrict default ignore</programlisting>
<note>
<para>This will also prevent access from the server to
any servers listed in the local configuration. If there is
a need to synchronise the NTP server with an external NTP
server, allow only that specific server. See the
&man.ntp.conf.5; manual for more information.</para>
</note>
<para>To allow machines within the
network to synchronize their clocks with the server, but
ensure they are not allowed to configure the server or used
as peers to synchronize against, add</para>
<programlisting>restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap</programlisting>
<para>instead, where <hostid
role="ipaddr">192.168.1.0</hostid> is an IP address on
the network and <hostid
role="netmask">255.255.255.0</hostid> is the network's
netmask.</para>
<para>The <filename>/etc/ntp.conf</filename> file can contain
multiple <literal>restrict</literal> options. For more
details, see the <literal>Access Control Support</literal>
subsection of &man.ntp.conf.5;.</para>
</sect3>
</sect2>
<sect2>
<title>Running the NTP Server</title>
<para>To ensure the NTP server is started at boot time, add the
line <literal>ntpd_enable="YES"</literal> to
<filename>/etc/rc.conf</filename>. To pass
additional flags to &man.ntpd.8;, edit the
<varname>ntpd_flags</varname> parameter in
<filename>/etc/rc.conf</filename>.</para>
<para>To start the server without rebooting the machine, run
<command>ntpd</command> being sure to specify any additional
parameters from <varname>ntpd_flags</varname> in
<filename>/etc/rc.conf</filename>. For example:</para>
<screen>&prompt.root; <userinput>ntpd -p /var/run/ntpd.pid</userinput></screen>
</sect2>
<sect2>
<title>Using <application>ntpd</application> with a Temporary
Internet Connection</title>
<para>The &man.ntpd.8; program does not need a permanent
connection to the Internet to function properly. However, if
there is a temporary connection that is configured to dial out
on demand, it is a good idea to prevent NTP traffic from
triggering a dial out or keeping the connection alive. PPP
users can use the <literal>filter</literal>
directives in <filename>/etc/ppp/ppp.conf</filename>. For
example:</para>
<programlisting> set filter dial 0 deny udp src eq 123
# Prevent NTP traffic from initiating dial out
set filter dial 1 permit 0 0
set filter alive 0 deny udp src eq 123
# Prevent incoming NTP traffic from keeping the connection open
set filter alive 1 deny udp dst eq 123
# Prevent outgoing NTP traffic from keeping the connection open
set filter alive 2 permit 0/0 0/0</programlisting>
<para>For more details see the <literal>PACKET
FILTERING</literal> section in &man.ppp.8; and the examples
in <filename>/usr/share/examples/ppp/</filename>.</para>
<note>
<para>Some Internet access providers block low-numbered ports,
preventing NTP from functioning since replies never
reach the machine.</para>
</note>
</sect2>
<sect2>
<title>Further Information</title>
<para>Documentation for the NTP server can be found in
<filename>/usr/share/doc/ntp/</filename> in HTML
format.</para>
</sect2>
</sect1>
<sect1 id="network-syslogd">
<sect1info>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
<title>Remote Host Logging with <command>syslogd</command></title>
<para>Interacting with system logs is a crucial aspect of both
security and system administration. Monitoring the log files of
multiple hosts can get very unwieldy when these hosts are
distributed across medium or large networks, or when they are
parts of various different types of networks. In these cases,
configuring remote logging may make the whole process a lot more
comfortable.</para>
<para>Centralized logging to a specific logging host can reduce
some of the administrative burden of log file administration.
Log file aggregation, merging and rotation may be configured in
one location, using the native tools of &os;, such as
&man.syslogd.8; and &man.newsyslog.8;. In the following example
configuration, host <hostid>A</hostid>, named <hostid
role="fqdn">logserv.example.com</hostid>, will collect
logging information for the local network. Host
<hostid>B</hostid>, named <hostid
role="fqdn">logclient.example.com</hostid> will pass
logging information to the server system. In live
configurations, both hosts require proper forward and reverse
<acronym>DNS</acronym> or entries in
<filename>/etc/hosts</filename>. Otherwise, data will be
rejected by the server.</para>
<sect2>
<title>Log Server Configuration</title>
<para>Log servers are machines configured to accept logging
information from remote hosts. In most cases this is to ease
configuration, in other cases it may just be a better
administration move. Regardless of reason, there are a few
requirements before continuing.</para>
<para>A properly configured logging server has met the following
minimal requirements:</para>
<itemizedlist>
<listitem>
<para>The firewall ruleset allows for <acronym>UDP</acronym>
to be passed on port 514 on both the client and
server;</para>
</listitem>
<listitem>
<para><command>syslogd</command> has been configured to
accept remote messages from client machines;</para>
</listitem>
<listitem>
<para>The <command>syslogd</command> server and all client
machines must have valid entries for both forward and
reverse <acronym>DNS</acronym>, or be properly configured
in <filename>/etc/hosts</filename>.</para>
</listitem>
</itemizedlist>
<para>To configure the log server, the client must be listed
in <filename>/etc/syslog.conf</filename>, and the logging
facility must be specified:</para>
<programlisting>+logclient.example.com
*.* /var/log/logclient.log</programlisting>
<note>
<para>More information on various supported and available
<emphasis>facilities</emphasis> may be found in the
&man.syslog.conf.5; manual page.</para>
</note>
<para>Once added, all <literal>facility</literal> messages will
be logged to the file specified previously,
<filename>/var/log/logclient.log</filename>.</para>
<para>The server machine must also have the following listing
placed inside <filename>/etc/rc.conf</filename>:</para>
<programlisting>syslogd_enable="YES"
syslogd_flags="-a logclient.example.com -v -v"</programlisting>
<para>The first option will enable the
<command>syslogd</command> daemon on boot up, and the second
option allows data from the specified client to be accepted on
this server. The latter part, using <option>-v -v</option>,
will increase the verbosity of logged messages. This is
extremely useful for tweaking facilities as administrators are
able to see what type of messages are being logged under which
facility.</para>
<para>Multiple <option>-a</option> options may be specified to
allow logging from multiple clients. <acronym>IP</acronym>
addresses and whole netblocks may also be specified, see the
&man.syslog.3; manual page for a full list of possible
options.</para>
<para>Finally, the log file should be created. The method used
does not matter, but &man.touch.1; works great for situations
such as this:</para>
<screen>&prompt.root; <userinput><command>touch</command>
<filename>/var/log/logclient.log</filename></userinput></screen>
<para>At this point, the <command>syslogd</command> daemon
should be restarted and verified:</para>
<screen>&prompt.root; <userinput>service <command>syslogd</command> restart</userinput>
&prompt.root; <userinput><command>pgrep</command> syslog</userinput></screen>
<para>If a <acronym>PID</acronym> is returned, the server has
been restarted successfully, and client configuration may
begin. If the server has not restarted, consult the
<filename>/var/log/messages</filename> log for any
output.</para>
</sect2>
<sect2>
<title>Log Client Configuration</title>
<para>A logging client is a machine which sends log information
to a logging server in addition to keeping local
copies.</para>
<para>Similar to log servers, clients must also meet a few
minimum requirements:</para>
<itemizedlist>
<listitem>
<para>&man.syslogd.8; must be configured to send messages of
specific types to a log server, which must accept
them;</para>
</listitem>
<listitem>
<para>The firewall must allow <acronym>UDP</acronym> packets
through on port 514;</para>
</listitem>
<listitem>
<para>Both forward and reverse <acronym>DNS</acronym> must
be configured or have proper entries in the
<filename>/etc/hosts</filename>.</para>
</listitem>
</itemizedlist>
<para>Client configuration is a bit more relaxed when compared
to that of the servers. The client machine must have the
following listing placed inside
<filename>/etc/rc.conf</filename>:</para>
<programlisting>syslogd_enable="YES"
syslogd_flags="-s -v -v"</programlisting>
<para>As before, these entries will enable the
<command>syslogd</command> daemon on boot up, and increases
the verbosity of logged messages. The <option>-s</option>
option prevents logs from being accepted by this client from
other hosts.</para>
<para>Facilities describe the system part for which a message
is generated. For an example, <acronym>ftp</acronym> and
<acronym>ipfw</acronym> are both facilities. When log
messages are generated for those two services, they will
normally include those two utilities in any log messages.
Facilities are accompanied with a priority or level, which
is used to mark how important a log message is. The most
common will be the <literal>warning</literal> and
<literal>info</literal>. Please refer to the &man.syslog.3;
manual page for a full list of available facilities and
priorities.</para>
<para>The logging server must be defined in the client's
<filename>/etc/syslog.conf</filename>. In this instance,
the <literal>@</literal> symbol is used to send logging
data to a remote server and would look similar to the
following entry:</para>
<programlisting>*.* @logserv.example.com</programlisting>
<para>Once added, <command>syslogd</command> must be restarted
for the changes to take effect:</para>
<screen>&prompt.root; <userinput>service <command>syslogd</command> restart</userinput></screen>
<para>To test that log messages are being sent across the
network, use &man.logger.1; on the client to send a message to
<command>syslogd</command>:</para>
<screen>&prompt.root; <userinput><command>logger</command>
"<replaceable>Test message from logclient</replaceable>"</userinput></screen>
<para>This message should now exist both in
<filename>/var/log/messages</filename> on the client, and
<filename>/var/log/logclient.log</filename> on the
log server.</para>
</sect2>
<sect2>
<title>Debugging Log Servers</title>
<para>In certain cases, debugging may be required if messages
are not being received on the log server. There are several
reasons this may occur; however, the most common two are
network connection issues and <acronym>DNS</acronym> issues.
To test these cases, ensure both hosts are able to reach one
another using the hostname specified in
<filename>/etc/rc.conf</filename>. If this appears to be
working properly, an alternation to the
<literal>syslogd_flags</literal> option in
<filename>/etc/rc.conf</filename> will be required.</para>
<para>In the following example,
<filename>/var/log/logclient.log</filename> is empty, and the
<filename>/var/log/messages</filename> files indicate no
reason for the failure. To increase debugging output, change
the <literal>syslogd_flags</literal> option to look like the
following example, and issue a restart:</para>
<programlisting>syslogd_flags="-d -a logclien.example.com -v -v"</programlisting>
<screen>&prompt.root; <userinput>service <command>syslogd</command> restart</userinput></screen>
<para>Debugging data similar to the following will flash on the
screen immediately after the restart:</para>
<screen>logmsg: pri 56, flags 4, from logserv.example.com, msg syslogd: restart
syslogd: restarted
logmsg: pri 6, flags 4, from logserv.example.com, msg syslogd: kernel boot file is /boot/kernel/kernel
Logging to FILE /var/log/messages
syslogd: kernel boot file is /boot/kernel/kernel
cvthname(192.168.1.10)
validate: dgram from IP 192.168.1.10, port 514, name logclient.example.com;
rejected in rule 0 due to name mismatch.</screen>
<para>It appears obvious the messages are being rejected due
to a name mismatch. After reviewing the configuration bit
by bit, it appears a typo in the following
<filename>/etc/rc.conf</filename> line has an issue:</para>
<programlisting>syslogd_flags="-d -a logclien.example.com -v -v"</programlisting>
<para>The line should contain <literal>logclient</literal>, not
<literal>logclien</literal>. After the proper alterations
are made, a restart is issued with expected results:</para>
<screen>&prompt.root; <userinput>service <command>syslogd</command> restart</userinput>
logmsg: pri 56, flags 4, from logserv.example.com, msg syslogd: restart
syslogd: restarted
logmsg: pri 6, flags 4, from logserv.example.com, msg syslogd: kernel boot file is /boot/kernel/kernel
syslogd: kernel boot file is /boot/kernel/kernel
logmsg: pri 166, flags 17, from logserv.example.com,
msg Dec 10 20:55:02 &lt;syslog.err&gt; logserv.example.com syslogd: exiting on signal 2
cvthname(192.168.1.10)
validate: dgram from IP 192.168.1.10, port 514, name logclient.example.com;
accepted in rule 0.
logmsg: pri 15, flags 0, from logclient.example.com, msg Dec 11 02:01:28 trhodes: Test message 2
Logging to FILE /var/log/logclient.log
Logging to FILE /var/log/messages</screen>
<para>At this point, the messages are being properly received
and placed in the correct file.</para>
</sect2>
<sect2>
<title>Security Considerations</title>
<para>As with any network service, security requirements should
be considered before implementing this configuration. At
times, log files may contain sensitive data about services
enabled on the local host, user accounts, and configuration
data. Network data sent from the client to the server will
not be encrypted nor password protected. If a need for
encryption exists, it might be possible to use
<filename role="package">security/stunnel</filename>, which
will transmit data over an encrypted tunnel.</para>
<para>Local security is also an issue. Log files are not
encrypted during use or after log rotation. Local users may
access these files to gain additional insight on system
configuration. In those cases, setting proper permissions
on these files will be critical. The &man.newsyslog.8;
utility supports setting permissions on newly created and
rotated log files. Setting log files to mode
<literal>600</literal> should prevent any unwanted snooping
by local users.</para>
</sect2>
</sect1>
</chapter>
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