[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[b06ca36] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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[673b0d8] | 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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[b78c747] | 7 |
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[4e82d47] | 8 | <sect1 id="ch-bootable-grub" role="wrap">
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[b78c747] | 9 | <?dbhtml filename="grub.html"?>
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| 10 |
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[4e82d47] | 11 | <sect1info condition="script">
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| 12 | <productname>grub</productname>
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| 13 | <productnumber>&grub-version;</productnumber>
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| 14 | <address>&grub-url;</address>
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| 15 | </sect1info>
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| 16 |
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[f9bcaec] | 17 | <title>Using GRUB to Set Up the Boot Process</title>
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[4e82d47] | 18 |
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[f9bcaec] | 19 | <sect2>
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| 20 | <title>Introduction</title>
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[4e82d47] | 21 |
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[483838e] | 22 | <warning><para>Configuring GRUB incorrectly can render your system
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| 23 | inoperable without an alternate boot device such as a CD-ROM. This
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| 24 | section is not required to boot your LFS system. You may just
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| 25 | want to modify your current boot loader, e.g. Grub-Legacy, GRUB2, or
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| 26 | LILO.</para></warning>
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| 27 |
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| 28 |
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| 29 | <para> Ensure that an emergency boot disk is ready to
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[4e82d47] | 30 | <quote>rescue</quote> the computer if the computer becomes
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[483838e] | 31 | unusable (un-bootable). If you do not already have a boot device,
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| 32 | you can create one. In order for the procedure below to work,
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| 33 | you need to jump ahead to BLFS and install <ulink
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| 34 | url="http://www.linuxfromscratch.org/blfs/view/svn/multimedia/xorriso.html">
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| 35 | xorriso</ulink>.</para>
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[4e82d47] | 36 |
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[483838e] | 37 | <screen role="nodump"><userinput>cd /tmp &&
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| 38 | grub-mkrescue --output=grub-img.iso &&
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| 39 | xorriso -as cdrecord -v dev=/dev/cdrw blank=as_needed grub-img.iso</userinput></screen>
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[1561534] | 40 |
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[483838e] | 41 | </sect2>
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[154c0ce] | 42 |
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[483838e] | 43 | <sect2>
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| 44 | <title>GRUB Naming Conventions</title>
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[1561534] | 45 |
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[4e82d47] | 46 | <para>GRUB uses its own naming structure for drives and partitions in
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| 47 | the form of <emphasis>(hdn,m)</emphasis>, where <emphasis>n</emphasis>
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| 48 | is the hard drive number and <emphasis>m</emphasis> is the partition
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[920932e] | 49 | number. The hard drive number starts from zero, but the partition number
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[f9bcaec] | 50 | starts from one for normal partitions and five for extended partitions.
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[920932e] | 51 | Note that this is different from earlier versions where
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[f9bcaec] | 52 | both numbers started from zero. For example, partition <filename
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| 53 | class="partition">sda1</filename> is <emphasis>(hd0,1)</emphasis> to
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| 54 | GRUB and <filename class="partition">sdb3</filename> is
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| 55 | <emphasis>(hd1,3)</emphasis>. In contrast to Linux, GRUB does not
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[4e82d47] | 56 | consider CD-ROM drives to be hard drives. For example, if using a CD
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| 57 | on <filename class="partition">hdb</filename> and a second hard drive
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| 58 | on <filename class="partition">hdc</filename>, that second hard drive
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| 59 | would still be <emphasis>(hd1)</emphasis>.</para>
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| 60 |
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[f9bcaec] | 61 | <para>You can determine what GRUB thinks your disk devices are by running:</para>
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| 62 |
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[6ea017a2] | 63 | <screen role="nodump"><userinput>grub-mkdevicemap --device-map=device.map
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[f9bcaec] | 64 | cat device.map</userinput></screen>
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| 65 |
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[483838e] | 66 | </sect2>
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| 67 |
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| 68 | <sect2>
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| 69 | <title>Setting Up the Configuration</title>
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| 70 |
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| 71 | <para>GRUB works by writing data to the first physical track of the
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| 72 | hard disk. This area is not part of any file system. The programs
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| 73 | there access GRUB modules in the boot partition. The default location
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| 74 | is /boot/grub/.</para>
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| 75 |
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[f9bcaec] | 76 | <para>The location of the boot partition is a choice of the user that
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| 77 | affects the configuration. One recommendation is to have a separate small
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| 78 | (suggested size is 100 MB) partition just for boot information. That way
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| 79 | each build, whether LFS or some commercial distro, can access the same boot
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| 80 | files and access can be made from any booted system. If you choose to do
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| 81 | this, you will need to mount the separate partition, move all files in the
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| 82 | current <filename class="directory">/boot</filename> directory (e.g. the
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| 83 | linux kernel you just built in the previous section) to the new partition.
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| 84 | You will then need to unmount the partition and remount it as <filename
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| 85 | class="directory">/boot</filename>. If you do this, be sure to update
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| 86 | <filename>/etc/fstab</filename>.</para>
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| 87 |
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| 88 | <para>Using the current lfs partition will also work, but configuration
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| 89 | for multiple systems is more difficult.</para>
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| 90 |
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[4e82d47] | 91 | <para>Using the above information, determine the appropriate
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| 92 | designator for the root partition (or boot partition, if a separate
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| 93 | one is used). For the following example, it is assumed that the root
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| 94 | (or separate boot) partition is <filename
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[f9bcaec] | 95 | class="partition">sda2</filename>.</para>
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| 96 |
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| 97 | <para>Install the GRUB files into <filename
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[483838e] | 98 | class="directory">/boot/grub</filename> and set up the boot track:</para>
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[f9bcaec] | 99 |
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[483838e] | 100 | <warning>
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| 101 | <para>The following command will overwrite the current boot loader. Do not
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| 102 | run the command if this is not desired, for example, if using a third party
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| 103 | boot manager to manage the Master Boot Record (MBR).</para>
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| 104 | </warning>
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[f9bcaec] | 105 |
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[483838e] | 106 | <screen role="nodump"><userinput>grub-install /dev/sda</userinput></screen>
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[f9bcaec] | 107 |
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[483838e] | 108 | <note><para><application>grub-install</application> is a script and calls another
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| 109 | program, grub-probe, that may fail with a message "cannot stat `/dev/root'".
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| 110 | If so, create a temporary symbolic link from your root partition to /dev/root:</para>
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[f9bcaec] | 111 |
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[483838e] | 112 | <screen role="nodump"><userinput>ln -sv /dev/sda2 /dev/root</userinput></screen>
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[f9bcaec] | 113 |
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[483838e] | 114 | <para>The symbolic link will only be present until the system is rebooted.
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| 115 | The link is only needed for the installation procedure.
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| 116 | </para></note>
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[4e82d47] | 117 |
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[f9bcaec] | 118 | </sect2>
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| 119 |
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| 120 | <sect2>
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[483838e] | 121 | <title>Creating the Configuration File</title>
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[1561534] | 122 |
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[483838e] | 123 | <para>Generate <filename>/boot/grub/grub.cfg</filename>:</para>
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[1561534] | 124 |
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[483838e] | 125 | <screen><userinput>cat > /boot/grub/grub.cfg << "EOF"
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| 126 | <literal># Begin /boot/grub/grub.cfg
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| 127 | set default=0
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| 128 | set timeout=5
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[1561534] | 129 |
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[483838e] | 130 | insmod ext2
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| 131 | set root=(hd0,2)
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[1561534] | 132 |
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[483838e] | 133 | menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" {
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[fe1643e] | 134 | linux /boot/vmlinuz-&linux-version;-lfs-&version; root=/dev/sda2 ro
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[483838e] | 135 | }</literal>
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| 136 | EOF</userinput></screen>
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| 137 |
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| 138 | <para>GRUB is an extremely powerful program and it provides a tremendous
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| 139 | number of options for booting from a wide variety of devices, operating
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| 140 | systems, and partition types. There are also many options for customization
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| 141 | such as graphical splash screens, playing sounds, mouse input, etc. The
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| 142 | details of these options are beyond the scope of this introduction.</para>
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| 143 |
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| 144 | <note><para>There is a command, <application>grub-mkconfig</application> that
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| 145 | can write a configuration file automatically. It uses a set of scripts in
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| 146 | /etc/grub.d/ and will destroy any customizations that you make. These scripts
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| 147 | are designed primarily for non-source distributions and are not recommended for
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| 148 | LFS. If you install a commercial Linux distribution, there is a good chance
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| 149 | that this program will be run. Be sure to back up your grub.cfg file.</para></note>
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[312e7dd] | 150 |
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[f9bcaec] | 151 | </sect2>
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[4e82d47] | 152 |
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[955533b] | 153 | </sect1>
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