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diff --git a/en_US.ISO8859-1/books/handbook/boot/chapter.sgml b/en_US.ISO8859-1/books/handbook/boot/chapter.sgml deleted file mode 100644 index d1c2c988c8..0000000000 --- a/en_US.ISO8859-1/books/handbook/boot/chapter.sgml +++ /dev/null @@ -1,549 +0,0 @@ -<!-- - The FreeBSD Documentation Project - - $FreeBSD: doc/en_US.ISO_8859-1/books/handbook/boot/chapter.sgml,v 1.9 2000/11/26 05:16:52 dannyboy Exp $ ---> - -<chapter id="boot"> - <title>The FreeBSD Booting Process</title> - - <sect1 id="boot-synopsis"> - <title>Synopsis</title> - - <para>FreeBSD uses a three-stage bootstrap by default, which - basically entails three programs which call each - other in order (two <link linkend="boot-blocks">boot - blocks</link>, and the <link - linkend="boot-loader">loader</link>). Each of these three build on the - previous program's understanding and provide increasing amounts - of sophistication.</para> - - <para>The kernel is then started, which will then 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 - then mounts filesystems, sets up network cards to act 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 Blocks: Bootstrap Stages 1 and 2</title> - - <para><firstterm>Bootstrapping</firstterm> is the process - whereby a computer probes and initializes its devices, and - works out what programs it is supposed to run.</para> - - <para>This involves the use of special Read Only Memory chips, - which determine what further operations to do, and these - usually pass control to other chips that do consistency and - memory tests, configure devices, and provide a mechanism for - programs to determine what configuration details were - determined.</para> - - <para>In standard personal computers, this involves the BIOS - (which oversees the bootstrap), and CMOS (which stores - configuration). BIOS and CMOS understand disks, and also - understand where on the disk to find a program that will know - how to load up an operating system.</para> - - <para>This chapter will not deal with this first part of the - bootstrap process. Instead it will focus on what happens after control - is passed to the program on the disk.</para> - - <para>The boot blocks are responsible for finding (usually) the - loader, and running it, and thus need to understand how to - find that program on the filesystem, how to run the program, - and also allow minor configuration of how they work.</para> - - <sect2 id="boot-boot0"> - <title>boot0</title> - - <para>There is actually a preceding bootblock, named boot0, - which lives on the <firstterm>Master Boot - Record</firstterm>, the special part of the disk that the - system bootstrap looks for and runs, and it simply shows a - list of possible slices to boot from.</para> - - <para>boot0 is very simple, since the program in the - <abbrev>MBR</abbrev> can only be 512 bytes in size.</para> - - <para>It displays something like this:</para> - - <example id="boot-boot0-example"> - <title>boot0 screenshot</title> - - <screen> -F1 DOS -F2 FreeBSD -F3 Linux -F4 ?? -F5 Drive 1 - -Default: F2</screen> - </example> - </sect2> - - <sect2 id="boot-boot1"> - <title>boot1</title> - - <para>boot1 is found on the boot sector of the boot slice, - which is where <link linkend="boot-boot0">boot0</link>, or - any other program on the <abbrev>MBR</abbrev> expects to - find the program to run to continue the boot process.</para> - - <para>boot1 is very simple, since it too can only be 512 bytes - in size, and knows just enough about the FreeBSD - <firstterm>disklabel</firstterm>, which stores information - about the slice, to find and execute <link - linkend="boot-boot2">boot2</link>.</para> - </sect2> - - <sect2 id="boot-boot2"> - <title>boot2</title> - - <para>boot2 is slightly more sophisticated, and understands - the FreeBSD filesystem 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, boot2 usually runs it, but previously it - was tasked to run the kernel directly.</para> - - <example id="boot-boot2-example"> - <title>boot2 screenshot</title> - - <screen>>> FreeBSD/i386 BOOT -Default: 0:wd(0,a)/kernel -boot:</screen> - </example> - </sect2> - </sect1> - - <sect1 id="boot-loader"> - <title>Loader: Bootstrap Stage Three</title> - - <para>The loader is the final stage of the three-stage - bootstrap, and is located on the filesystem, usually as - <filename>/boot/loader</filename>.</para> - - <note> - <para>While <filename>/boot/boot0</filename>, - <filename>/boot/boot1</filename>, and - <filename>/boot/boot2</filename> are files there, they are - not the actual copies in the <abbrev>MBR</abbrev>, the boot - sector, or the disklabel respectively.</para> - </note> - - <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> - - <sect2 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 then - the interpreter is started, and the easy-to-use commands are - explained to it.</para> - - <para>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> - - <para>A more technical discussion of the process is available - in &man.loader.8;</para> - </sect2> - - <sect2 id="boot-loader-commands"> - <title>Loader Built-In Commands</title> - - <para>The easy-to-use command set comprises of:</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 timespan 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.</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>Display 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>Set loader's environment variables.</para> - </listitem> - </varlistentry> - - <varlistentry> - <term>unload</term> - - <listitem> - <para>Removes all loaded modules.</para> - </listitem> - </varlistentry> - </variablelist> - </sect2> - - <sect2 id="boot-loader-examples"> - <title>Loader Examples</title> - - <para>Here are some practical examples of loader usage.</para> - - <itemizedlist> - <listitem> - <para>To simply 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> - - <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've 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'd normally do in the - kernel boot-time configurator):</para> - - <screen><userinput>load -t userconfig_script - <replaceable>/boot/kernel.conf</replaceable></userinput></screen> - </listitem> - </itemizedlist> - </sect2> - </sect1> - - <sect1 id="boot-kernel"> - <title>Kernel Interaction During Boot</title> - - <para>Once the kernel is loaded by either <link - linkend="boot-loader">loader</link> (as usual) or <link - linkend="boot-boot2">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> - - <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 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="boot-init"> - <title>Init: Process Control Initialization</title> - - <para>Once the kernel has finished booting, it passes control to - the user process <command>init</command>, 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 - filesystems available on the system are consistent. If they - are not, and <command>fsck</command> can not fix the - inconsistencies, <command>init</command> 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> - - <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> or setting the - <envar>boot_single</envar> variable in - <command>loader</command>.</para> - - <para>It can also be reached by calling - <command>shutdown</command> 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 console <literal>console</literal> is set - to <literal>insecure</literal> in - <filename>/etc/ttys</filename>, then the system prompts for - the root password before initiating single-user mode.</para> - - <example id="boot-insecure-console"> - <title>An insecure console in /etc/ttys</title> - - <programlisting># name getty type status comments -# -# This entry needed for asking password when init goes to single-user mode -# If you want to be asked for password, change "secure" to "insecure" here -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 - root 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> - - <para>If <command>init</command> finds your filesystems 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> - - <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 filesystems mentioned in - <filename>/etc/fstab</filename>, start up networking - services, starts up miscellaneous system daemons, and - finally runs the startup scripts of locally installed - packages.</para> - - <para>&man.rc.8; 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> - - <para>Upon controlled shutdown, via <command>shutdown</command>, - <command>init</command> will attempt to run the script - <filename>/etc/rc.shutdown</filename>, and then proceed to send - all processes the terminate signal, and subsequently the kill - signal to any that don't terminate timely.</para> - </sect1> -</chapter> - -<!-- - Local Variables: - mode: sgml - sgml-declaration: "../chapter.decl" - sgml-indent-data: t - sgml-omittag: nil - sgml-always-quote-attributes: t - sgml-parent-document: ("../book.sgml" "part" "chapter") - End: ---> - |