source: chapter10/grub.xml@ cefb4c9

11.0 11.0-rc1 11.0-rc2 11.0-rc3 11.1 11.1-rc1 arm ml-11.0 multilib trunk xry111/clfs-ng xry111/glibc-2.34 xry111/lfs-next
Last change on this file since cefb4c9 was cefb4c9, checked in by Xi Ruoyao <xry111@…>, 11 months ago

grub cfg: replace hardcoded (and outdated) chapter number

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 %general-entities;
6]>
7
8<sect1 id="ch-bootable-grub" role="wrap">
9 <?dbhtml filename="grub.html"?>
10
11 <sect1info condition="script">
12 <productname>grub</productname>
13 <productnumber>&grub-version;</productnumber>
14 <address>&grub-url;</address>
15 </sect1info>
16
17 <title>Using GRUB to Set Up the Boot Process</title>
18
19 <note>
20 <para>
21 If your system has UEFI support and you wish to boot LFS with UEFI,
22 you should skip this page, and config GRUB with UEFI support
23 using the instructions provided in
24 <ulink url="&blfs-book;postlfs/grub-setup.html">the BLFS page</ulink>.
25 </para>
26 </note>
27
28 <sect2>
29 <title>Introduction</title>
30
31 <warning><para>Configuring GRUB incorrectly can render your system
32 inoperable without an alternate boot device such as a CD-ROM or bootable
33 USB drive. This section is not required to boot your LFS system. You may
34 just want to modify your current boot loader, e.g. Grub-Legacy, GRUB2, or
35 LILO.</para></warning>
36
37 <para> Ensure that an emergency boot disk is ready to <quote>rescue</quote>
38 the computer if the computer becomes unusable (un-bootable). If you do not
39 already have a boot device, you can create one. In order for the procedure
40 below to work, you need to jump ahead to BLFS and install
41 <userinput>xorriso</userinput> from the <ulink
42 url="&blfs-book;multimedia/libisoburn.html">
43 libisoburn</ulink> package.</para>
44
45<screen role="nodump"><userinput>cd /tmp
46grub-mkrescue --output=grub-img.iso
47xorriso -as cdrecord -v dev=/dev/cdrw blank=as_needed grub-img.iso</userinput></screen>
48
49 </sect2>
50
51 <sect2>
52 <title>GRUB Naming Conventions</title>
53
54 <para>GRUB uses its own naming structure for drives and partitions in
55 the form of <emphasis>(hdn,m)</emphasis>, where <emphasis>n</emphasis>
56 is the hard drive number and <emphasis>m</emphasis> is the partition
57 number. The hard drive number starts from zero, but the partition number
58 starts from one for normal partitions and five for extended partitions.
59 Note that this is different from earlier versions where
60 both numbers started from zero. For example, partition <filename
61 class="partition">sda1</filename> is <emphasis>(hd0,1)</emphasis> to
62 GRUB and <filename class="partition">sdb3</filename> is
63 <emphasis>(hd1,3)</emphasis>. In contrast to Linux, GRUB does not
64 consider CD-ROM drives to be hard drives. For example, if using a CD
65 on <filename class="partition">hdb</filename> and a second hard drive
66 on <filename class="partition">hdc</filename>, that second hard drive
67 would still be <emphasis>(hd1)</emphasis>.</para>
68
69 </sect2>
70
71 <sect2>
72 <title>Setting Up the Configuration</title>
73
74 <para>GRUB works by writing data to the first physical track of the
75 hard disk. This area is not part of any file system. The programs
76 there access GRUB modules in the boot partition. The default location
77 is /boot/grub/.</para>
78
79 <para>The location of the boot partition is a choice of the user that
80 affects the configuration. One recommendation is to have a separate small
81 (suggested size is 200 MB) partition just for boot information. That way
82 each build, whether LFS or some commercial distro, can access the same boot
83 files and access can be made from any booted system. If you choose to do
84 this, you will need to mount the separate partition, move all files in the
85 current <filename class="directory">/boot</filename> directory (e.g. the
86 linux kernel you just built in the previous section) to the new partition.
87 You will then need to unmount the partition and remount it as <filename
88 class="directory">/boot</filename>. If you do this, be sure to update
89 <filename>/etc/fstab</filename>.</para>
90
91 <para>Using the current lfs partition will also work, but configuration
92 for multiple systems is more difficult.</para>
93
94 <para>Using the above information, determine the appropriate
95 designator for the root partition (or boot partition, if a separate
96 one is used). For the following example, it is assumed that the root
97 (or separate boot) partition is <filename
98 class="partition">sda2</filename>.</para>
99
100 <para>Install the GRUB files into <filename
101 class="directory">/boot/grub</filename> and set up the boot track:</para>
102
103 <warning>
104 <para>The following command will overwrite the current boot loader. Do not
105 run the command if this is not desired, for example, if using a third party
106 boot manager to manage the Master Boot Record (MBR).</para>
107 </warning>
108
109<screen role="nodump"><userinput>grub-install /dev/sda</userinput></screen>
110
111 <note>
112 <para>If the system has been booted using UEFI,
113 <command>grub-install</command> will try to install files for the
114 <emphasis>x86_64-efi</emphasis> target, but those files
115 have not been installed in <xref linkend="chapter-building-system"/>.
116 If this is the case, add <option>--target i386-pc</option> to the
117 command above.</para>
118 </note>
119
120<!-- This does not seem to be true any more
121 <note><para><application>grub-install</application> is a script and calls another
122 program, grub-probe, that may fail with a message "cannot stat `/dev/root'".
123 If so, create a temporary symbolic link from your root partition to /dev/root:</para>
124
125<screen role="nodump"><userinput>ln -sv /dev/sda2 /dev/root</userinput></screen>
126
127 <para>The symbolic link will only be present until the system is rebooted.
128 The link is only needed for the installation procedure.
129 </para></note>
130-->
131 </sect2>
132
133 <sect2 id="grub-cfg">
134 <title>Creating the GRUB Configuration File</title>
135
136 <para>Generate <filename>/boot/grub/grub.cfg</filename>:</para>
137
138 <screen revision="sysv"><userinput>cat &gt; /boot/grub/grub.cfg &lt;&lt; "EOF"
139<literal># Begin /boot/grub/grub.cfg
140set default=0
141set timeout=5
142
143insmod ext2
144set root=(hd0,2)
145
146menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" {
147 linux /boot/vmlinuz-&linux-version;-lfs-&version; root=/dev/sda2 ro
148}</literal>
149EOF</userinput></screen>
150
151 <screen revision="systemd"><userinput>cat &gt; /boot/grub/grub.cfg &lt;&lt; "EOF"
152<literal># Begin /boot/grub/grub.cfg
153set default=0
154set timeout=5
155
156insmod ext2
157set root=(hd0,2)
158
159menuentry "GNU/Linux, Linux &linux-version;-lfs-&versiond;" {
160 linux /boot/vmlinuz-&linux-version;-lfs-&versiond; root=/dev/sda2 ro
161}</literal>
162EOF</userinput></screen>
163
164
165 <note><para>From <application>GRUB</application>'s perspective, the
166 kernel files are relative to the partition used. If you
167 used a separate /boot partition, remove /boot from the above
168 <emphasis>linux</emphasis> line. You will also need to change the
169 <emphasis>set root</emphasis> line to point to the boot partition.
170 </para></note>
171
172 <para>GRUB is an extremely powerful program and it provides a tremendous
173 number of options for booting from a wide variety of devices, operating
174 systems, and partition types. There are also many options for customization
175 such as graphical splash screens, playing sounds, mouse input, etc. The
176 details of these options are beyond the scope of this introduction.</para>
177
178 <caution><para>There is a command, <application>grub-mkconfig</application>, that
179 can write a configuration file automatically. It uses a set of scripts in
180 /etc/grub.d/ and will destroy any customizations that you make. These scripts
181 are designed primarily for non-source distributions and are not recommended for
182 LFS. If you install a commercial Linux distribution, there is a good chance
183 that this program will be run. Be sure to back up your grub.cfg file.</para></caution>
184
185 </sect2>
186
187</sect1>
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