<?xml version="1.0" encoding="iso-8859-1"?>
<!--
The FreeBSD Documentation Project
$FreeBSD$
-->
<chapter id="boot">
<title>The FreeBSD Booting Process</title>
<sect1 id="boot-synopsis">
<title>Synopsis</title>
<indexterm><primary>booting</primary></indexterm>
<indexterm><primary>bootstrap</primary></indexterm>
<para>The process of starting a computer and loading the operating
system is referred to as <quote>the bootstrap process</quote>,
or simply <quote>booting</quote>. FreeBSD's boot process
provides a great deal of flexibility in customizing what happens
when you start the system, allowing you to select from different
operating systems installed on the same computer, or even
different versions of the same operating system or installed
kernel.</para>
<para>This chapter details the configuration options you can set
and how to customize the FreeBSD boot process. This includes
everything that happens until the FreeBSD kernel has started,
probed for devices, and started &man.init.8;. If you are not
quite sure when this happens, it occurs when the text color
changes from bright white to grey.</para>
<para>After reading this chapter, you will know:</para>
<itemizedlist>
<listitem>
<para>What the components of the FreeBSD bootstrap system are,
and how they interact.</para>
</listitem>
<listitem>
<para>The options you can give to the components in the
FreeBSD bootstrap to control the boot process.</para>
</listitem>
<listitem>
<para>The basics of &man.device.hints.5;.</para>
</listitem>
</itemizedlist>
<note>
<title>x86 Only</title>
<para>This chapter only describes the boot process for FreeBSD
running on Intel x86 systems.</para>
</note>
</sect1>
<sect1 id="boot-introduction">
<title>The Booting Problem</title>
<para>Turning on a computer and starting the operating system
poses an interesting dilemma. By definition, the computer does
not know how to do anything until the operating system is
started. This includes running programs from the disk. So if
the computer can not run a program from the disk without the
operating system, and the operating system programs are on the
disk, how is the operating system started?</para>
<para>This problem parallels one in the book <citetitle>The
Adventures of Baron Munchausen</citetitle>. A character had
fallen part way down a manhole, and pulled himself out by
grabbing his bootstraps, and lifting. In the early days of
computing the term <firstterm>bootstrap</firstterm> was applied
to the mechanism used to load the operating system, which has
become shortened to <quote>booting</quote>.</para>
<indexterm><primary>BIOS</primary></indexterm>
<indexterm>
<primary>Basic Input/Output System</primary>
<see>BIOS</see>
</indexterm>
<para>On x86 hardware the Basic Input/Output System (BIOS) is
responsible for loading the operating system. To do this, the
BIOS looks on the hard disk for the Master Boot Record (MBR),
which must be located on a specific place on the disk. The BIOS
has enough knowledge to load and run the MBR, and assumes that
the MBR can then carry out the rest of the tasks involved in
loading the operating system, possibly with the help of the
BIOS.</para>
<indexterm><primary>Master Boot Record (MBR)</primary></indexterm>
<indexterm><primary>Boot Manager</primary></indexterm>
<indexterm><primary>Boot Loader</primary></indexterm>
<para>The code within the MBR is usually referred to as a
<emphasis>boot manager</emphasis>, especially when it interacts
with the user. In this case the boot manager usually has more
code in the first <emphasis>track</emphasis> of the disk or
within some OS's file system. (A boot manager is sometimes also
called a <emphasis>boot loader</emphasis>, but FreeBSD uses that
term for a later stage of booting.) Popular boot managers
include <application>boot0</application> (aka
<application>Boot Easy</application>, the standard &os; boot
manager), <application>Grub</application>,
<application>GAG</application>, and
<application>LILO</application>. (Only
<application>boot0</application> fits within the MBR.)</para>
<para>If you have only one operating system installed on your
disks then a standard PC MBR will suffice. This MBR searches
for the first bootable (aka active) slice on the disk, and
then runs the code on that slice to load the remainder of the
operating system. The MBR installed by &man.fdisk.8;, by
default, is such an MBR. It is based on
<filename>/boot/mbr</filename>.</para>
<para>If you have installed multiple operating systems on your
disks then you can install a different boot manager, one that
can display a list of different operating systems, and allows
you to choose the one to boot from. Two of these are discussed
in the next subsection.</para>
<para>The remainder of the FreeBSD bootstrap system is divided
into three stages. The first stage is run by the MBR, which
knows just enough to get the computer into a specific state and
run the second stage. The second stage can do a little bit
more, before running the third stage. The third stage finishes
the task of loading the operating system. The work is split
into these three stages because the PC standards put limits on
the size of the programs that can be run at stages one and two.
Chaining the tasks together allows FreeBSD to provide a more
flexible loader.</para>
<indexterm><primary>kernel</primary></indexterm>
<indexterm><primary><command>init</command></primary></indexterm>
<para>The kernel is then started and it begins to probe for
devices and initialize them for use. Once the kernel boot
process is finished, the kernel passes control to the user
process &man.init.8;, which then makes sure the disks are in a
usable state. &man.init.8; then starts the user-level resource
configuration which mounts file systems, sets up network cards
to communicate on the network, and generally starts all the
processes that usually are run on a FreeBSD system at
startup.</para>
</sect1>
<sect1 id="boot-blocks">
<title>The Boot Manager and Boot Stages</title>
<indexterm><primary>Boot Manager</primary></indexterm>
<sect2 id="boot-boot0">
<title>The Boot Manager</title>
<indexterm><primary>Master Boot Record
(MBR)</primary></indexterm>
<para>The code in the MBR or boot manager is sometimes referred
to as <emphasis>stage zero</emphasis> of the boot process.
This subsection discusses two of the boot managers previously
mentioned: <application>boot0</application> and
<application>LILO</application>.</para>
<formalpara>
<title>The <application>boot0</application> Boot
Manager:</title>
<para>The MBR installed by FreeBSD's installer or
&man.boot0cfg.8;, by default, is based on
<filename>/boot/boot0</filename>. (The
<application>boot0</application> program is very simple,
since the program in the <abbrev>MBR</abbrev> can only be
446 bytes long because of the slice table and
<literal>0x55AA</literal> identifier at the end of the MBR.)
If you have installed <application>boot0</application> and
multiple operating systems on your hard disks, then you will
see a display similar to this one at boot
time:</para>
</formalpara>
<example id="boot-boot0-example">
<title><filename>boot0</filename> Screenshot</title>
<screen>F1 DOS
F2 FreeBSD
F3 Linux
F4 ??
F5 Drive 1
Default: F2</screen>
</example>
<para>Other operating systems, in particular &windows;, have
been known to overwrite an existing MBR with their own. If
this happens to you, or you want to replace your existing MBR
with the FreeBSD MBR then use the following command:</para>
<screen>&prompt.root; <userinput>fdisk -B -b /boot/boot0 <replaceable>device</replaceable></userinput></screen>
<para>where <replaceable>device</replaceable> is the device that
you boot from, such as <devicename>ad0</devicename> for the
first IDE disk, <devicename>ad2</devicename> for the first IDE
disk on a second IDE controller, <devicename>da0</devicename>
for the first SCSI disk, and so on. Or, if you want a custom
configuration of the MBR, use &man.boot0cfg.8;.</para>
<formalpara>
<title>The LILO Boot Manager:</title>
<para>To install this boot manager so it will also boot
FreeBSD, first start Linux and add the following to your
existing <filename>/etc/lilo.conf</filename> configuration
file:</para>
</formalpara>
<programlisting>other=/dev/hdXY
table=/dev/hdX
loader=/boot/chain.b
label=FreeBSD</programlisting>
<para>In the above, specify FreeBSD's primary partition and
drive using Linux specifiers, replacing
<replaceable>X</replaceable> with the Linux drive letter and
<replaceable>Y</replaceable> with the Linux primary partition
number. If you are using a <acronym>SCSI</acronym> drive, you
will need to change <replaceable>/dev/hd</replaceable> to read
something similar to <replaceable>/dev/sd</replaceable>. The
<option>loader=/boot/chain.b</option> line can be omitted if
you have both operating systems on the same drive. Now run
<command>/sbin/lilo -v</command> to commit your new
changes to the system; this should be verified by checking its
screen messages.</para>
</sect2>
<sect2 id="boot-boot1">
<title>Stage One, <filename>/boot/boot1</filename>, and Stage
Two, <filename>/boot/boot2</filename></title>
<para>Conceptually the first and second stages are part of the
same program, on the same area of the disk. Because of space
constraints they have been split into two, but you would
always install them together. They are copied from the
combined file <filename>/boot/boot</filename> by the installer
or <application>bsdlabel</application> (see below).</para>
<para>They are located outside file systems, in the first track
of the boot slice, starting with the first sector. This is
where <link linkend="boot-boot0">boot0</link>, or any other
boot manager, expects to find a program to run which will
continue the boot process. The number of sectors used is
easily determined from the size of
<filename>/boot/boot</filename>.</para>
<para><filename>boot1</filename> is very simple, since it can
only be 512 bytes in size, and knows just enough about the
FreeBSD <firstterm>bsdlabel</firstterm>, which stores
information about the slice, to find and execute
<filename>boot2</filename>.</para>
<para><filename>boot2</filename> is slightly more sophisticated,
and understands the FreeBSD file system enough to find files
on it, and can provide a simple interface to choose the kernel
or loader to run.</para>
<para>Since the <link linkend="boot-loader">loader</link> is
much more sophisticated, and provides a nice easy-to-use
boot configuration, <filename>boot2</filename> usually runs
it, but previously it
was tasked to run the kernel directly.</para>
<example id="boot-boot2-example">
<title><filename>boot2</filename> Screenshot</title>
<screen>>> FreeBSD/i386 BOOT
Default: 0:ad(0,a)/boot/loader
boot:</screen>
</example>
<para>If you ever need to replace the installed
<filename>boot1</filename> and <filename>boot2</filename> use
&man.bsdlabel.8;:</para>
<screen>&prompt.root; <userinput>bsdlabel -B <replaceable>diskslice</replaceable></userinput></screen>
<para>where <replaceable>diskslice</replaceable> is the disk and
slice you boot from, such as <devicename>ad0s1</devicename>
for the first slice on the first IDE disk.</para>
<warning>
<title>Dangerously Dedicated Mode</title>
<para>If you use just the disk name, such as
<devicename>ad0</devicename>, in the &man.bsdlabel.8;
command you will create a dangerously dedicated disk,
without slices. This is almost certainly not what you want
to do, so make sure you double check the &man.bsdlabel.8;
command before you press <keycap>Return</keycap>.</para>
</warning>
</sect2>
<sect2 id="boot-loader">
<title>Stage Three, <filename>/boot/loader</filename></title>
<indexterm><primary>boot-loader</primary></indexterm>
<para>The loader is the final stage of the three-stage
bootstrap, and is located on the file system, usually as
<filename>/boot/loader</filename>.</para>
<para>The loader is intended as a user-friendly method for
configuration, using an easy-to-use built-in command set,
backed up by a more powerful interpreter, with a more complex
command set.</para>
<sect3 id="boot-loader-flow">
<title>Loader Program Flow</title>
<para>During initialization, the loader will probe for a
console and for disks, and figure out what disk it is
booting from. It will set variables accordingly, and an
interpreter is started where user commands can be passed
from a script or interactively.</para>
<indexterm><primary>loader</primary></indexterm>
<indexterm><primary>loader configuration</primary></indexterm>
<para>The loader will then read
<filename>/boot/loader.rc</filename>, which by default reads
in <filename>/boot/defaults/loader.conf</filename> which
sets reasonable defaults for variables and reads
<filename>/boot/loader.conf</filename> for local changes to
those variables. <filename>loader.rc</filename> then acts
on these variables, loading whichever modules and kernel are
selected.</para>
<para>Finally, by default, the loader issues a 10 second wait
for key presses, and boots the kernel if it is not
interrupted. If interrupted, the user is presented with a
prompt which understands the easy-to-use command set, where
the user may adjust variables, unload all modules, load
modules, and then finally boot or reboot.</para>
</sect3>
<sect3 id="boot-loader-commands">
<title>Loader Built-In Commands</title>
<para>These are the most commonly used loader commands. For a
complete discussion of all available commands, please see
&man.loader.8;.</para>
<variablelist>
<varlistentry>
<term>autoboot <replaceable>seconds</replaceable></term>
<listitem>
<para>Proceeds to boot the kernel if not interrupted
within the time span given, in seconds. It displays a
countdown, and the default time span is 10
seconds.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>boot
<optional><replaceable>-options</replaceable></optional>
<optional><replaceable>kernelname</replaceable></optional></term>
<listitem>
<para>Immediately proceeds to boot the kernel, with the
given options, if any, and with the kernel name given,
if it is. Providing a kernel name on the command-line
is only applicable after an
<emphasis>unload</emphasis> command has been issued,
otherwise the previously-loaded kernel will be
used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>boot-conf</term>
<listitem>
<para>Goes through the same automatic configuration of
modules based on variables as what happens at boot.
This only makes sense if you use
<command>unload</command> first, and change some
variables, most commonly <envar>kernel</envar>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>help
<optional><replaceable>topic</replaceable></optional></term>
<listitem>
<para>Shows help messages read from
<filename>/boot/loader.help</filename>. If the topic
given is <literal>index</literal>, then the list of
available topics is given.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>include <replaceable>filename</replaceable>
…</term>
<listitem>
<para>Processes the file with the given filename. The
file is read in, and interpreted line by line. An
error immediately stops the include command.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>load <optional><option>-t</option>
<replaceable>type</replaceable></optional>
<replaceable>filename</replaceable></term>
<listitem>
<para>Loads the kernel, kernel module, or file of the
type given, with the filename given. Any arguments
after filename are passed to the file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ls <optional><option>-l</option></optional>
<optional><replaceable>path</replaceable></optional></term>
<listitem>
<para>Displays a listing of files in the given path, or
the root directory, if the path is not specified. If
<option>-l</option> is specified, file sizes will be
shown too.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>lsdev
<optional><option>-v</option></optional></term>
<listitem>
<para>Lists all of the devices from which it may be
possible to load modules. If <option>-v</option> is
specified, more details are printed.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>lsmod
<optional><option>-v</option></optional></term>
<listitem>
<para>Displays loaded modules. If <option>-v</option>
is specified, more details are shown.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>more <replaceable>filename</replaceable></term>
<listitem>
<para>Displays the files specified, with a pause at each
<varname>LINES</varname> displayed.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>reboot</term>
<listitem>
<para>Immediately reboots the system.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>set <replaceable>variable</replaceable></term>
<term>set
<replaceable>variable</replaceable>=<replaceable>value</replaceable></term>
<listitem>
<para>Sets the loader's environment variables.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>unload</term>
<listitem>
<para>Removes all loaded modules.</para>
</listitem>
</varlistentry>
</variablelist>
</sect3>
<sect3 id="boot-loader-examples">
<title>Loader Examples</title>
<para>Here are some practical examples of loader usage:</para>
<itemizedlist>
<indexterm><primary>single-user mode</primary></indexterm>
<listitem>
<para>To boot your usual kernel, but in single-user
mode:</para>
<screen><userinput>boot -s</userinput></screen>
</listitem>
<listitem>
<para>To unload your usual kernel and modules, and then
load just your old (or another) kernel:</para>
<indexterm>
<primary><filename>kernel.old</filename></primary>
</indexterm>
<screen><userinput>unload</userinput>
<userinput>load <replaceable>kernel.old</replaceable></userinput></screen>
<para>You can use <filename>kernel.GENERIC</filename> to
refer to the generic kernel that comes on the install
disk, or <filename>kernel.old</filename> to refer to
your previously installed kernel (when you have upgraded
or configured your own kernel, for example).</para>
<note>
<para>Use the following to load your usual modules with
another kernel:</para>
<screen><userinput>unload</userinput>
<userinput>set kernel="<replaceable>kernel.old</replaceable>"</userinput>
<userinput>boot-conf</userinput></screen></note>
</listitem>
<listitem>
<para>To load a kernel configuration script (an automated
script which does the things you would normally do in
the kernel boot-time configurator):</para>
<screen><userinput>load -t userconfig_script <replaceable>/boot/kernel.conf</replaceable></userinput></screen>
</listitem>
</itemizedlist>
</sect3>
<sect3 id="boot-splash">
<sect3info>
<authorgroup>
<author>
<firstname>Joseph J.</firstname>
<surname>Barbish</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect3info>
<title>Boot Time Splash Screens</title>
<para>The splash screen creates a more visually appealing boot
screen compared to the original boot messages. This screen
will be displayed until a console login prompt or an X
display manager offers a login prompt.</para>
<para>There are two basic environments available in &os;. The
first is the default legacy virtual console command line
environment. After the system finishes booting, a console
login prompt is presented. The second environment is the
X11 Desktop graphical environment. After
<link linkend="x-install">X11</link> and one of the
graphical
<link linkend="x11-wm">desktop environments</link>, such as
<application>GNOME</application>,
<application>KDE</application>, or
<application>XFce</application> are installed, the X11
desktop can be launched by using
<command>startx</command>.</para>
<para>Some users prefer the X11 graphical login screen over
the traditional text based login prompt. Display managers
like <application>XDM</application> for &xorg;,
<application>gdm</application> for
<application>GNOME</application>, and
<application>kdm</application> for
<application>KDE</application> (and any other from the Ports
Collection) provide a graphical login screen in
place of the console login prompt. After a successful
login, they present the user with a graphical
desktop.</para>
<para>In the command line environment, the splash screen would
hide all the boot probe messages and task startup messages
before displaying the login prompt. In X11 environment, the
users would get a visually clearer system start up
experience resembling something closer to what a
(µsoft; &windows; or non-unix type system) user would
experience.</para>
<sect4 id="boot-splash-function">
<title>Splash Screen Function</title>
<para>The splash screen function supports 256-color
bitmap (<filename>.bmp</filename>), ZSoft
<acronym>PCX</acronym> (<filename>.pcx</filename>), or
TheDraw (<filename>.bin</filename>) files.
In addition, the splash image files must have a resolution
of 320 by 200 pixels or less to work on standard VGA
adapters.</para>
<para>To use larger images, up to the maximum resolution of
1024 by 768 pixels, activate the <acronym>VESA</acronym>
support included in &os;. This can be enabled by loading
the <acronym>VESA</acronym> module during system boot, or
adding a <literal>VESA</literal> kernel configuration
option and building a custom kernel (see <xref
linkend="kernelconfig"/>). The <acronym>VESA</acronym>
support gives users the ability to display a splash screen
image that fills the whole display screen.</para>
<para>While the splash screen is being displayed during the
booting process, it can be turned off any time by hitting
any key on the keyboard.</para>
<para>The splash screen also defaults to being a screen
saver outside of X11. After a time period of non-use the
screen will change to the splash screen and cycle through
steps of changing intensity of the image, from bright to a
very dark and over again. This default splash screen
(screen saver) behavior could be overridden by adding a
<literal>saver=</literal> line to
<filename>/etc/rc.conf</filename>. Option
<literal>saver=</literal> has several built-in screen
savers to choose from, the full list can be found in the
&man.splash.4; manual page. The default screen saver is
called <quote>warp</quote>. Note that the
<literal>saver=</literal> option specified in
<filename>/etc/rc.conf</filename> only applies to virtual
consoles. It has no effect on X11 display
managers.</para>
<para>A few boot loader messages, including the boot options
menu and a timed wait count down prompt are displayed at
boot time, even when the splash screen is enabled.</para>
<para>Sample splash screen files can be downloaded from the
gallery at <ulink
url="http://artwork.freebsdgr.org/node/3/">http://artwork.freebsdgr.org</ulink>.
By installing the <filename
role="package">sysutils/bsd-splash-changer</filename>
port, splash images can be chosen from a collection
randomly at each boot.</para>
</sect4>
<sect4 id="boot-splash-enable">
<title>Enabling the Splash Screen Function</title>
<para>The splash screen (<filename>.bmp</filename>,
<filename>.pcx</filename>, or <filename>.bin</filename>)
file has to be placed on the root partition, for example
in the <filename class="directory">/boot</filename>
directory.</para>
<para>For default boot display resolution (256-color, 320 by
200 pixels, or less), edit
<filename>/boot/loader.conf</filename>, so it contains the
following:</para>
<programlisting>splash_bmp_load="YES"
bitmap_load="YES"
bitmap_name="<replaceable>/boot/splash.bmp</replaceable>"</programlisting>
<para>For larger video resolutions up to the maximum of 1024
by 768 pixels, edit
<filename>/boot/loader.conf</filename>, so it contains the
following:</para>
<programlisting>vesa_load="YES"
splash_bmp_load="YES"
bitmap_load="YES"
bitmap_name="<replaceable>/boot/splash.bmp</replaceable>"</programlisting>
<para>The above assumes that
<filename><replaceable>/boot/splash.bmp</replaceable></filename>
is used for splash screen. When a <acronym>PCX</acronym>
file is desired, use the following statements, plus the
<literal>vesa_load="YES"</literal> line depending on the
resolution.</para>
<programlisting>splash_pcx_load="YES"
bitmap_load="YES"
bitmap_name="<replaceable>/boot/splash.pcx</replaceable>"</programlisting>
<para>In version 8.3 another option is to use ascii art in
<ulink
url="https://en.wikipedia.org/wiki/TheDraw">TheDraw</ulink>
format.</para>
<programlisting>splash_txt="YES"
bitmap_load="YES"
bitmap_name="<replaceable>/boot/splash.bin</replaceable>"</programlisting>
<para>The file name is not restricted to
<quote>splash</quote> as shown in the above example. It
can be anything as long as it is one of the above types
such as,
<filename><replaceable>splash_640x400</replaceable>.bmp</filename>
or
<filename><replaceable>bluewave</replaceable>.pcx</filename>.</para>
<para>Some other interesting
<filename>loader.conf</filename> options:</para>
<variablelist>
<varlistentry>
<term><literal>beastie_disable="YES"</literal></term>
<listitem>
<para>This will stop the boot options menu from being
displayed, but the timed wait count down prompt will
still be present. Even with the display of the boot
options menu disabled, entering an option selection
at the timed wait count down prompt will enact the
corresponding boot option.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>loader_logo="beastie"</literal></term>
<listitem>
<para>This will replace the default words
<quote>&os;</quote>, which are displayed to the
right of the boot options menu with the colored
beastie logo like releases in the past had.</para>
</listitem>
</varlistentry>
</variablelist>
<para>For more information, please see the &man.splash.4;,
&man.loader.conf.5;, and &man.vga.4; manual pages.</para>
</sect4>
</sect3>
</sect2>
</sect1>
<sect1 id="boot-kernel">
<title>Kernel Interaction During Boot</title>
<indexterm>
<primary>kernel</primary>
<secondary>boot interaction</secondary>
</indexterm>
<para>Once the kernel is loaded by either <link
linkend="boot-loader">loader</link> (as usual) or <link
linkend="boot-boot1">boot2</link> (bypassing the loader), it
examines its boot flags, if any, and adjusts its behavior as
necessary.</para>
<sect2 id="boot-kernel-bootflags">
<title>Kernel Boot Flags</title>
<indexterm>
<primary>kernel</primary>
<secondary>bootflags</secondary>
</indexterm>
<para>Here are the more common boot flags:</para>
<variablelist id="boot-kernel-bootflags-list">
<varlistentry>
<term><option>-a</option></term>
<listitem>
<para>during kernel initialization, ask for the device
to mount as the root file system.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-C</option></term>
<listitem>
<para>boot from CDROM.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-c</option></term>
<listitem>
<para>run UserConfig, the boot-time kernel
configurator</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s</option></term>
<listitem>
<para>boot into single-user mode</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-v</option></term>
<listitem>
<para>be more verbose during kernel startup</para>
</listitem>
</varlistentry>
</variablelist>
<note>
<para>There are other boot flags, read &man.boot.8; for more
information on them.</para>
</note>
</sect2>
<!-- <sect2 id="boot-kernel-userconfig">
<title>UserConfig: the Boot-time Kernel Configurator</title>
<para> </para>
</sect2> -->
</sect1>
<sect1 id="device-hints">
<sect1info>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
<!-- 18 OCT 2002 -->
</sect1info>
<title>Device Hints</title>
<indexterm>
<primary>device.hints</primary>
</indexterm>
<para>During initial system startup, the boot &man.loader.8; will
read the &man.device.hints.5; file. This file stores kernel
boot information known as variables, sometimes referred to as
<quote>device hints</quote>. These <quote>device hints</quote>
are used by device drivers for device configuration.</para>
<para>Device hints may also be specified at the
<link linkend="boot-loader">
Stage 3 boot loader</link> prompt. Variables can be added using
<command>set</command>, removed with <command>unset</command>,
and viewed with the <command>show</command> commands. Variables
set in <filename>/boot/device.hints</filename> can be
overridden here also. Device hints entered at the boot loader
are not permanent and will be forgotten on the next
reboot.</para>
<para>Once the system is booted, the &man.kenv.1; command can be
used to dump all of the variables.</para>
<para>The syntax for <filename>/boot/device.hints</filename>
is one variable per line, using the standard hash
<quote>#</quote> as comment markers. Lines are constructed as
follows:</para>
<screen><userinput>hint.driver.unit.keyword="<replaceable>value</replaceable>"</userinput></screen>
<para>The syntax for the Stage 3 boot loader is:</para>
<screen><userinput>set hint.driver.unit.keyword=<replaceable>value</replaceable></userinput></screen>
<para><literal>driver</literal> is the device driver name,
<literal>unit</literal> is the device driver unit number, and
<literal>keyword</literal> is the hint keyword. The keyword may
consist of the following options:</para>
<itemizedlist>
<listitem>
<para><literal>at</literal>: specifies the bus which the
device is attached to.</para>
</listitem>
<listitem>
<para><literal>port</literal>: specifies the start address of
the <acronym>I/O</acronym> to be used.</para>
</listitem>
<listitem>
<para><literal>irq</literal>: specifies the interrupt request
number to be used.</para>
</listitem>
<listitem>
<para><literal>drq</literal>: specifies the DMA channel
number.</para>
</listitem>
<listitem>
<para><literal>maddr</literal>: specifies the physical memory
address occupied by the device.</para>
</listitem>
<listitem>
<para><literal>flags</literal>: sets various flag bits for the
device.</para>
</listitem>
<listitem>
<para><literal>disabled</literal>: if set to
<literal>1</literal> the device is disabled.</para>
</listitem>
</itemizedlist>
<para>Device drivers may accept (or require) more hints not listed
here, viewing their manual page is recommended. For more
information, consult the &man.device.hints.5;, &man.kenv.1;,
&man.loader.conf.5;, and &man.loader.8; manual pages.</para>
</sect1>
<sect1 id="boot-init">
<title>Init: Process Control Initialization</title>
<indexterm>
<primary><command>init</command></primary>
</indexterm>
<para>Once the kernel has finished booting, it passes control to
the user process &man.init.8;, which is located at
<filename>/sbin/init</filename>, or the program path specified
in the <envar>init_path</envar> variable in
<command>loader</command>.</para>
<sect2 id="boot-autoreboot">
<title>Automatic Reboot Sequence</title>
<para>The automatic reboot sequence makes sure that the file
systems available on the system are consistent. If they are
not, and &man.fsck.8; cannot fix the inconsistencies,
&man.init.8; drops the system into
<link linkend="boot-singleuser">single-user mode</link> for
the system administrator to take care of the problems
directly.</para>
</sect2>
<sect2 id="boot-singleuser">
<title>Single-User Mode</title>
<indexterm><primary>single-user mode</primary></indexterm>
<indexterm><primary>console</primary></indexterm>
<para>This mode can be reached through the
<link linkend="boot-autoreboot">automatic reboot
sequence</link>, or by the user booting with the
<option>-s</option> option or setting the
<envar>boot_single</envar> variable in
<command>loader</command>.</para>
<para>It can also be reached by calling &man.shutdown.8; without
the reboot (<option>-r</option>) or halt (<option>-h</option>)
options, from <link linkend="boot-multiuser">multi-user
mode</link>.</para>
<para>If the system <literal>console</literal> is set to
<literal>insecure</literal> in <filename>/etc/ttys</filename>,
then the system prompts for the <username>root</username>
password before initiating single-user mode.</para>
<example id="boot-insecure-console">
<title>An Insecure Console in
<filename>/etc/ttys</filename></title>
<programlisting># name getty type status comments
#
# If console is marked "insecure", then init will ask for the root password
# when going to single-user mode.
console none unknown off insecure</programlisting>
</example>
<note>
<para>An <literal>insecure</literal> console means that you
consider your physical security to the console to be
insecure, and want to make sure only someone who knows the
<username>root</username> password may use single-user mode,
and it does not mean that you want to run your console
insecurely. Thus, if you want security, choose
<literal>insecure</literal>, not
<literal>secure</literal>.</para>
</note>
</sect2>
<sect2 id="boot-multiuser">
<title>Multi-User Mode</title>
<indexterm><primary>multi-user mode</primary></indexterm>
<para>If &man.init.8; finds your file systems to be in order, or
once the user has finished in <link
linkend="boot-singleuser">single-user mode</link>, the
system enters multi-user mode, in which it starts the
resource configuration of the system.</para>
<sect3 id="boot-rc">
<title>Resource Configuration (rc)</title>
<indexterm><primary>rc files</primary></indexterm>
<para>The resource configuration system reads in
configuration defaults from
<filename>/etc/defaults/rc.conf</filename>, and
system-specific details from
<filename>/etc/rc.conf</filename>, and then proceeds to
mount the system file systems mentioned in
<filename>/etc/fstab</filename>, start up networking
services, start up miscellaneous system daemons, and
finally runs the startup scripts of locally installed
packages.</para>
<para>The &man.rc.8; manual page is a good reference to the
resource configuration system, as is examining the scripts
themselves.</para>
</sect3>
</sect2>
</sect1>
<sect1 id="boot-shutdown">
<title>Shutdown Sequence</title>
<indexterm>
<primary><command>shutdown</command></primary>
</indexterm>
<para>Upon controlled shutdown, via &man.shutdown.8;,
&man.init.8; will attempt to run the script
<filename>/etc/rc.shutdown</filename>, and then proceed to send
all processes the <literal>TERM</literal> signal, and
subsequently the <literal>KILL</literal> signal to any that do
not terminate timely.</para>
<para>To power down a FreeBSD machine on architectures and systems
that support power management, use the command
<command>shutdown -p now</command> to turn the power off
immediately. To just reboot a FreeBSD system, just use
<command>shutdown -r now</command>. You need to be
<username>root</username> or a member of
<groupname>operator</groupname> group to run &man.shutdown.8;.
The &man.halt.8; and &man.reboot.8; commands can also be used,
please refer to their manual pages and to &man.shutdown.8;'s one
for more information.</para>
<note>
<para>Power management requires &man.acpi.4; support in the
kernel or loaded as module for.</para>
</note>
</sect1>
</chapter>