svn commit: r44623 - head/en_US.ISO8859-1/books/handbook/boot
Dru Lavigne
dru at FreeBSD.org
Mon Apr 21 22:51:02 UTC 2014
Author: dru
Date: Mon Apr 21 22:51:01 2014
New Revision: 44623
URL: http://svnweb.freebsd.org/changeset/doc/44623
Log:
Editorial review of boot stages.
Format loader built-in commands as a table.
More commits to come.
Sponsored by: iXsystems
Modified:
head/en_US.ISO8859-1/books/handbook/boot/chapter.xml
Modified: head/en_US.ISO8859-1/books/handbook/boot/chapter.xml
==============================================================================
--- head/en_US.ISO8859-1/books/handbook/boot/chapter.xml Mon Apr 21 21:29:57 2014 (r44622)
+++ head/en_US.ISO8859-1/books/handbook/boot/chapter.xml Mon Apr 21 22:51:01 2014 (r44623)
@@ -173,18 +173,13 @@
<indexterm><primary>Master Boot Record
(<acronym>MBR</acronym>)</primary></indexterm>
- <para>The code in the <acronym>MBR</acronym> or boot manager is
+ <para>The boot manager code in the <acronym>MBR</acronym> is
sometimes referred to as <emphasis>stage zero</emphasis> of the
- boot process. This section discusses two boot managers:
- <application>boot0</application> and
- <application>LILO</application>.</para>
-
- <formalpara>
- <title>The <application>boot0</application> Boot
- Manager:</title>
+ boot process. By default, &os; uses the
+ <application>boot0</application> boot manager.</para>
- <para>The <acronym>MBR</acronym> installed by &os;'s installer
- or &man.boot0cfg.8; is based on
+ <para>The <acronym>MBR</acronym> installed by the &os; installer
+ is based on
<filename>/boot/boot0</filename>. The size and capability of
<application>boot0</application> is restricted to 446 bytes
due to the slice table and <literal>0x55AA</literal>
@@ -192,7 +187,6 @@
<application>boot0</application> and multiple operating
systems are installed, a message similar to this example will
be displayed at boot time:</para>
- </formalpara>
<example xml:id="boot-boot0-example">
<title><filename>boot0</filename> Screenshot</title>
@@ -203,7 +197,7 @@ F2 FreeBSD
Default: F2</screen>
</example>
- <para>Other operating systems, in particular &windows;, will
+ <para>Other operating systems will
overwrite an existing <acronym>MBR</acronym> if they are
installed after &os;. If this happens, or to replace the
existing <acronym>MBR</acronym> with the &os;
@@ -219,65 +213,37 @@ Default: F2</screen>
for the first <acronym>SCSI</acronym> disk. To create a
custom configuration of the <acronym>MBR</acronym>, refer to
&man.boot0cfg.8;.</para>
-
- <formalpara>
- <title>The LILO Boot Manager:</title>
-
- <para>To install this boot manager so it will also boot &os;,
- boot into Linux and add the following to the existing
- <filename>/etc/lilo.conf</filename> configuration:</para>
- </formalpara>
-
- <programlisting>other=/dev/hdXY
-table=/dev/hdX
-loader=/boot/chain.b
-label=FreeBSD</programlisting>
-
- <para>Specify &os;'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. For a <acronym>SCSI</acronym>
- drive, change <replaceable>/dev/hd</replaceable> to
- <replaceable>/dev/sd</replaceable>. The
- <option>loader=/boot/chain.b</option> line can be omitted if
- both operating systems are installed on the same drive. Next,
- run <command>/sbin/lilo -v</command> to commit the new
- changes. Verify these are correct by checking the screen
- messages.</para>
</sect2>
<sect2 xml:id="boot-boot1">
<title>Stage One and Stage Two</title>
<para>Conceptually, the first and second stages are part of the
- same program, on the same area of the disk. Because of space
+ same program on the same area of the disk. Because of space
constraints, they have been split into two, but are always
installed together. They are copied from the combined
- <filename>/boot/boot</filename> by the installer or
- &man.bsdlabel.8;.</para>
+ <filename>/boot/boot</filename> by the &os; installer or
+ <command>bsdlabel</command>.</para>
- <para>They are located outside file systems, in the first track
+ <para>These two stages are located outside file systems, in the first track
of the boot slice, starting with the first sector. This is
- where boot0 (<xref linkend="boot-boot0"/>), or any other
+ where <application>boot0</application>, 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>
+ continue the boot process.</para>
- <para><filename>boot1</filename> is very simple, since it can
- only be 512 bytes in size, and knows just enough about the
+ <para>The first stage, <filename>boot1</filename>, is very simple, since it can
+ only be 512 bytes in size. It knows just enough about the
&os; <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 &os; file system enough to find files, and
+ <para>Stage two, <filename>boot2</filename>, is slightly more sophisticated,
+ and understands the &os; file system enough to find files. It
can provide a simple interface to choose the kernel or loader
- to run.</para>
-
- <para>However, &man.loader.8; is much more sophisticated and
- provides a boot configuration which is run by
- <filename>boot2</filename>.</para>
+ to run. It runs <application>loader</application>, which is much more sophisticated and
+ provides a boot configuration file. If the boot process is
+ interrupted at stage two, the following interactive screen is
+ displayed:</para>
<example xml:id="boot-boot2-example">
<title><filename>boot2</filename> Screenshot</title>
@@ -287,26 +253,23 @@ Default: 0:ad(0,a)/boot/loader
boot:</screen>
</example>
- <para>&man.bsdlabel.8; can be used to replace the installed
+ <para>To replace the installed
<filename>boot1</filename> and
- <filename>boot2</filename>:</para>
-
- <screen>&prompt.root; <userinput>bsdlabel -B <replaceable>diskslice</replaceable></userinput></screen>
-
- <para>where <replaceable>diskslice</replaceable> is the disk and
+ <filename>boot2</filename>, use <command>bsdlabel</command>,
+ where <replaceable>diskslice</replaceable> is the disk and
slice to boot from, such as <filename>ad0s1</filename>
for the first slice on the first <acronym>IDE</acronym>
- disk.</para>
+ disk:</para>
- <warning>
- <title>Dangerously Dedicated Mode</title>
+ <screen>&prompt.root; <userinput>bsdlabel -B <replaceable>diskslice</replaceable></userinput></screen>
+ <warning>
<para>If just the disk name is used, such as
- <filename>ad0</filename>, &man.bsdlabel.8; will create a
- <quote>dangerously dedicated</quote> disk, without slices.
+ <filename>ad0</filename>, <command>bsdlabel</command> will create the disk in
+ <quote>dangerously dedicated mode</quote>, without slices.
This is probably not the desired action, so double check the
- <replaceable>diskslice</replaceable> passed to
- &man.bsdlabel.8; before pressing
+ <replaceable>diskslice</replaceable>
+ before pressing
<keycap>Return</keycap>.</para>
</warning>
</sect2>
@@ -316,16 +279,16 @@ boot:</screen>
<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
+ <para>The <application>loader</application> is the final stage of the three-stage
+ bootstrap process. It is located on the file system, usually as
<filename>/boot/loader</filename>.</para>
- <para>The loader is intended as an interactive method for
+ <para>The <application>loader</application> is intended as an interactive method for
configuration, using a built-in command set, backed up by a
more powerful interpreter which has a more complex command
set.</para>
- <para>During initialization, the loader will probe for a
+ <para>During initialization, <application>loader</application> will probe for a
console and for disks, and figure out which disk it is
booting from. It will set variables accordingly, and an
interpreter is started where user commands can be passed from
@@ -334,7 +297,7 @@ boot:</screen>
<indexterm><primary>loader</primary></indexterm>
<indexterm><primary>loader configuration</primary></indexterm>
- <para>The loader will then read
+ <para>The <application>loader</application> 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
@@ -343,166 +306,135 @@ boot:</screen>
these variables, loading whichever modules and kernel are
selected.</para>
- <para>Finally, by default, the loader issues a 10 second wait
+ <para>Finally, by default, <application>loader</application> 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 command set, where the user may
adjust variables, unload all modules, load modules, and then
- finally boot or reboot.</para>
+ finally boot or reboot. <xref
+ linkend="boot-loader-commands"/> lists the most
+ commonly used <application>loader</application> commands. For
+ a complete discussion of all available commands, refer to
+ &man.loader.8;.</para>
- <sect3 xml:id="boot-loader-commands">
+ <table xml:id="boot-loader-commands" frame="none" pgwide="1">
<title>Loader Built-In Commands</title>
- <para>These are the most commonly used loader commands. For a
- complete discussion of all available commands, refer to
- &man.loader.8;.</para>
-
- <variablelist>
- <varlistentry>
- <term>autoboot <replaceable>seconds</replaceable></term>
-
- <listitem>
- <para>Proceeds to boot the kernel if not interrupted
+ <tgroup cols="2">
+ <thead>
+ <row>
+ <entry>Variable</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>autoboot <replaceable>seconds</replaceable></entry>
+ <entry>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>
+ seconds.</entry>
+ </row>
- <varlistentry>
- <term>boot
+ <row>
+ <entry>boot
<optional><replaceable>-options</replaceable></optional>
- <optional><replaceable>kernelname</replaceable></optional></term>
-
- <listitem>
- <para>Immediately proceeds to boot the kernel, with any
+ <optional><replaceable>kernelname</replaceable></optional></entry>
+ <entry>Immediately proceeds to boot the kernel, with any
specified options or kernel name. 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
+ <command>unload</command> has been issued.
+ Otherwise the previously-loaded kernel will be
+ used.</entry>
+ </row>
+
+ <row>
+ <entry>boot-conf</entry>
+ <entry>Goes through the same automatic configuration of
modules based on specified variables, most commonly
<envar>kernel</envar>. This only makes sense if
<command>unload</command> is used first, before
- changing some variables.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>help
- <optional><replaceable>topic</replaceable></optional></term>
+ changing some variables.</entry>
+ </row>
- <listitem>
- <para>Shows help messages read from
+ <row>
+ <entry>help
+ <optional><replaceable>topic</replaceable></optional></entry>
+ <entry>Shows help messages read from
<filename>/boot/loader.help</filename>. If the topic
given is <literal>index</literal>, the list of
- available topics is displayed.</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>
+ available topics is displayed.</entry>
+ </row>
- <varlistentry>
- <term>load <optional>-t
- <replaceable>type</replaceable></optional>
- <replaceable>filename</replaceable></term>
+ <row>
+ <entry>include <replaceable>filename</replaceable>
+ …</entry>
+ <entry>Reads the specified file and interprets it line by line. An
+ error immediately stops the <command>include</command>.</entry>
+ </row>
- <listitem>
- <para>Loads the kernel, kernel module, or file of the
+ <row>
+ <entry>load <optional>-t
+ <replaceable>type</replaceable></optional>
+ <replaceable>filename</replaceable></entry>
+ <entry>Loads the kernel, kernel module, or file of the
type given, with the specified filename. Any
arguments after <replaceable>filename</replaceable>
- are passed to the file.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>ls <optional>-l</optional>
- <optional><replaceable>path</replaceable></optional></term>
+ are passed to the file.</entry>
+ </row>
- <listitem>
- <para>Displays a listing of files in the given path, or
+ <row>
+ <entry>ls <optional>-l</optional>
+ <optional><replaceable>path</replaceable></optional></entry>
+ <entry>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
- also be shown.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>lsdev
- <optional>-v</optional></term>
+ also be shown.</entry>
+ </row>
- <listitem>
- <para>Lists all of the devices from which it may be
+ <row>
+ <entry>lsdev
+ <optional>-v</optional></entry>
+ <entry>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>-v</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>
+ specified, more details are printed.</entry>
+ </row>
+
+ <row>
+ <entry>lsmod
+ <optional>-v</optional></entry>
+ <entry>Displays loaded modules. If <option>-v</option>
+ is specified, more details are shown.</entry>
+ </row>
+
+ <row>
+ <entry>more <replaceable>filename</replaceable></entry>
+ <entry>Displays the files specified, with a pause at each
+ <varname>LINES</varname> displayed.</entry>
+ </row>
+
+ <row>
+ <entry>reboot</entry>
+ <entry>Immediately reboots the system.</entry>
+ </row>
+
+ <row>
+ <entry>set <replaceable>variable</replaceable>, set
+ <replaceable>variable</replaceable>=<replaceable>value</replaceable></entry>
+ <entry>Sets the specified environment variables.</entry>
+ </row>
+
+ <row>
+ <entry>unload</entry>
+ <entry>Removes all loaded modules.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </sect2>
- <sect3 xml:id="boot-loader-examples">
+ <sect2 xml:id="boot-loader-examples">
<title>Loader Examples</title>
<para>Here are some practical examples of loader usage:</para>
@@ -547,7 +479,6 @@ boot:</screen>
<screen><userinput>load -t userconfig_script <replaceable>/boot/kernel.conf</replaceable></userinput></screen>
</listitem>
</itemizedlist>
- </sect3>
</sect2>
<sect2 xml:id="boot-kernel">
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