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@@ -19,25 +19,29 @@
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<sect2>
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<title>Introduction</title>
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- <para>Boot loading can be a complex area, so a few cautionary
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- words are in order. Be familiar with the current boot loader and any other
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- operating systems present on the hard drive(s) that need to be
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- bootable. Make sure that an emergency boot disk is ready to
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+ <warning><para>Configuring GRUB incorrectly can render your system
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+ inoperable without an alternate boot device such as a CD-ROM. This
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+ section is not required to boot your LFS system. You may just
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+ want to modify your current boot loader, e.g. Grub-Legacy, GRUB2, or
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+ LILO.</para></warning>
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+
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+
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+ <para> Ensure that an emergency boot disk is ready to
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<quote>rescue</quote> the computer if the computer becomes
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- unusable (un-bootable).</para>
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+ unusable (un-bootable). If you do not already have a boot device,
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+ you can create one. In order for the procedure below to work,
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+ you need to jump ahead to BLFS and install <ulink
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+ url="http://www.linuxfromscratch.org/blfs/view/svn/multimedia/xorriso.html">
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+ xorriso</ulink>.</para>
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- <para>The procedure involves writing some special GRUB files to specific
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- locations on the hard drive. We highly recommend creating a GRUB boot
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- floppy diskette as a backup. Insert a blank floppy diskette and run the
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- following commands:</para>
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+<screen role="nodump"><userinput>cd /tmp &&
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+grub-mkrescue --output=grub-img.iso &&
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+xorriso -as cdrecord -v dev=/dev/cdrw blank=as_needed grub-img.iso</userinput></screen>
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-<screen role="nodump"><userinput>cd /tmp
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-grub-mkrescue --output=grub-img.iso
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-dd if=grub-img.iso of=/dev/fd0 bs=1440 count=1</userinput></screen>
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+ </sect2>
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- <para>Alternatively, a boot CD can be created by using your host system's
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- CD burning tools to burn the <filename>grub-img.iso</filename> on to a
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- blank CD.</para>
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+ <sect2>
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+ <title>GRUB Naming Conventions</title>
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<para>GRUB uses its own naming structure for drives and partitions in
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the form of <emphasis>(hdn,m)</emphasis>, where <emphasis>n</emphasis>
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@@ -59,6 +63,16 @@ dd if=grub-img.iso of=/dev/fd0 bs=1440 count=1</userinput></screen>
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<screen role="nodump"><userinput>grub-mkdevicemap --device-map=device.map
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cat device.map</userinput></screen>
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+ </sect2>
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+
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+ <sect2>
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+ <title>Setting Up the Configuration</title>
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+
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+ <para>GRUB works by writing data to the first physical track of the
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+ hard disk. This area is not part of any file system. The programs
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+ there access GRUB modules in the boot partition. The default location
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+ is /boot/grub/.</para>
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+
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<para>The location of the boot partition is a choice of the user that
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affects the configuration. One recommendation is to have a separate small
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(suggested size is 100 MB) partition just for boot information. That way
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@@ -73,10 +87,6 @@ cat device.map</userinput></screen>
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<para>Using the current lfs partition will also work, but configuration
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for multiple systems is more difficult.</para>
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- </sect2>
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-
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- <sect2>
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- <title>Setting Up the Configuration</title>
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<para>Using the above information, determine the appropriate
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designator for the root partition (or boot partition, if a separate
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@@ -85,175 +95,58 @@ cat device.map</userinput></screen>
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class="partition">sda2</filename>.</para>
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<para>Install the GRUB files into <filename
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- class="directory">/boot/grub</filename>:</para>
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-
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-<screen role="nodump"><userinput>grub-install --grub-setup=/bin/true /dev/sda</userinput></screen>
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-
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- <para>We use --grub-setup=/bin/true for now to prevent updating the
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- Master Boot Record (MBR). In this way, we can test our installation
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- before committing to a change that is hard to revert.</para>
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+ class="directory">/boot/grub</filename> and set up the boot track:</para>
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- <para>Generate <filename>/boot/grub/grub.cfg</filename>:</para>
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+ <warning>
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+ <para>The following command will overwrite the current boot loader. Do not
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+ run the command if this is not desired, for example, if using a third party
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+ boot manager to manage the Master Boot Record (MBR).</para>
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+ </warning>
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-<screen role="nodump"><userinput>grub-mkconfig -o /boot/grub/grub.cfg</userinput></screen>
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+<screen role="nodump"><userinput>grub-install /dev/sda</userinput></screen>
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- <para>Here <command>grub-mkconfig</command> uses the files in <filename
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- class="directory">/etc/grub.d/</filename> to determine the contents
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- of this file. The configuration file will look something like:</para>
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-<screen><computeroutput>#
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-# DO NOT EDIT THIS FILE
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-#
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-# It is automatically generated by /usr/sbin/grub-mkconfig using templates
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-# from /etc/grub.d and settings from /etc/default/grub
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-#
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+ <note><para><application>grub-install</application> is a script and calls another
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+ program, grub-probe, that may fail with a message "cannot stat `/dev/root'".
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+ If so, create a temporary symbolic link from your root partition to /dev/root:</para>
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-### BEGIN /etc/grub.d/00_header ###
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-set default=0
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-set timeout=5
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-### END /etc/grub.d/00_header ###
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+<screen role="nodump"><userinput>ln -sv /dev/sda2 /dev/root</userinput></screen>
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-### BEGIN /etc/grub.d/10_linux ###
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-menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" {
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- insmod ext2
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- set root=(hd0,2)
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- search --no-floppy --fs-uuid --set 915852a7-859e-45a6-9ff0-d3ebfdb5cea2
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- linux /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro
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-}
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-menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" (recovery mode)" {
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- insmod ext2
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- set root=(hd0,2)
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- search --no-floppy --fs-uuid --set 915852a7-859e-45a6-9ff0-d3ebfdb5cea2
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- linux /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro single
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-}
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-menuentry "GNU/Linux, Linux 2.6.28-11-server" {
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- insmod ext2
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- set root=(hd0,2)
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- search --no-floppy --fs-uuid --set 6b4c0339-5501-4a85-8351-e398e5252be8
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- linux /boot/vmlinuz-2.6.28-11-server root=UUID=6b4c0339-5501-4a85-8351-e398e5252be8 ro
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- initrd /boot/initrd.img-2.6.28-11-server
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-}
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-menuentry "GNU/Linux, Linux 2.6.28-11-server (recovery mode)" {
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- insmod ext2
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- set root=(hd0,2)
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- search --no-floppy --fs-uuid --set 6b4c0339-5501-4a85-8351-e398e5252be8
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- linux /boot/vmlinuz-2.6.28-11-server root=UUID=6b4c0339-5501-4a85-8351-e398e5252be8 ro single
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- initrd /boot/initrd.img-2.6.28-11-server
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-}
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-### END /etc/grub.d/10_linux ###
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-
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-### BEGIN /etc/grub.d/30_os-prober ###
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-### END /etc/grub.d/30_os-prober ###
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-
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-### BEGIN /etc/grub.d/40_custom ###
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-# This file provides an easy way to add custom menu entries. Simply type the
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-# menu entries you want to add after this comment. Be careful not to change
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-# the 'exec tail' line above.
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-### END /etc/grub.d/40_custom ###
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-</computeroutput></screen>
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-
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- <note>
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- <itemizedlist>
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- <listitem><para>Even though there is a warning not to edit the file, you
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- can do so as long as you do not re-run
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- <command>grub-mkconfig</command>.</para></listitem>
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-
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- <listitem><para>The <emphasis>search</emphasis> lines are generally not
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- useful for LFS systems as that command only sets an internal GRUB
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- variable used to find the kernel image. The <emphasis>set root</emphasis>
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- command provides the same capability without the overhead of
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- searching.</para></listitem>
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-
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- <listitem><para>The <emphasis>set root</emphasis> and
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- <emphasis>insmod ext2</emphasis> commands can be moved out of the
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- <emphasis>menuentry</emphasis> sections to apply to all sections of the file.
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- This leads to a simple section like:</para></listitem>
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-
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- </itemizedlist>
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-<screen><computeroutput>menuentry "Linux &linux-version;-lfs-&version;" {
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-linux /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro
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-}
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-</computeroutput></screen>
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-
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- <itemizedlist>
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-
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- <listitem><para>Passing a UUID to the kernel requires an initial ram disk
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- (initrd) not built by LFS.</para></listitem>
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-
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- <listitem><para>If the <filename>/boot</filename> partition is installed
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- on a separate partition, the linux and initrd lines should not have the
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- string <emphasis>/boot</emphasis> prefixed to the file
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- names.</para></listitem>
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-
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- <listitem><para>In this example the kernel files for a Ubuntu
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- installation are also found in <filename
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- class="directory">/boot</filename>.</para></listitem>
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-
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- </itemizedlist>
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- </note>
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+ <para>The symbolic link will only be present until the system is rebooted.
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+ The link is only needed for the installation procedure.
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+ </para></note>
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</sect2>
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-
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- <sect2>
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- <title>Testing the Configuration</title>
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-
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- <para>The core image of GRUB is also a Multiboot kernel, so if you already
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- have <emphasis>GRUB Legacy</emphasis> loaded you can load
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- GRUB-&grub-version; through your old boot loader. To accomplish this, you
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- will need to exit the <command>chroot</command> environment now and
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- re-enter it in the next section to finish the few remaining portions of
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- the book.</para>
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-
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-<screen role="nodump"><userinput>/sbin/reboot
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-...
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-grub> root (hd0,1)
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-grub> kernel /boot/grub/core.img
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-grub> boot</userinput></screen>
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-
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- <para>Note that the GRUB commands above are assumed to be GRUB Legacy.
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- At this point the GRUB prompt will appear (very similar to GRUB Legacy) and
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- you can explore the interface or boot to one of the systems in the grub.cfg
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- file.</para>
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-
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- </sect2>
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<sect2>
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- <title>Updating the Master Boot Record</title>
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-
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- <para>If you tested the GRUB configuration as specified above, re-enter
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- the <command>chroot</command> environment.</para>
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+ <title>Creating the Configuration File</title>
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- <warning>
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- <para>The following command will overwrite the current boot loader. Do not
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- run the command if this is not desired, for example, if using a third party
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- boot manager to manage the Master Boot Record (MBR).</para>
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- </warning>
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-
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- <para>Update the MBR with:</para>
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-
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-<screen role="nodump"><userinput>grub-setup '<DEVICE>'</userinput></screen>
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-
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- <para>Change the DEVICE above to your boot disk, normally '(hd0)' or /dev/sda.
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- If using (hd0) be sure to escape the parentheses with backslashes or single
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- quotes to prevent the shell from interpreting them as a sub-shell.</para>
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+ <para>Generate <filename>/boot/grub/grub.cfg</filename>:</para>
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- <para>This program uses the following defaults and are correct if you did not
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- deviate from the instructions above:</para>
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+ <screen><userinput>cat > /boot/grub/grub.cfg << "EOF"
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+<literal># Begin /boot/grub/grub.cfg
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+set default=0
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+set timeout=5
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- <itemizedlist>
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- <listitem><para>boot image - boot.img </para></listitem>
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- <listitem><para>core image - core.img </para></listitem>
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- <listitem><para>directory - /boot/grub</para></listitem>
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- <listitem><para>device map - device.map</para></listitem>
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- <listitem><para>default root setting - guessed</para></listitem>
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- </itemizedlist>
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+insmod ext2
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+set root=(hd0,2)
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- <note><para>The root setting is the default value if a 'set root'
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- instruction is not found in grub.cfg. This is the partition that is
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- searched for the kernel and other supporting files. It is different from
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- the 'root=' parameter on the 'linux' line in the configuration line. The
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- latter is the partition the kernel mounts as '/'. In the example grub.cfg
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- above, both values point to /dev/sda2, but if there is a separate boot
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- partition, they will be different.</para></note>
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+menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" {
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+ linux /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro
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+}</literal>
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+EOF</userinput></screen>
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+
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+ <para>GRUB is an extremely powerful program and it provides a tremendous
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+ number of options for booting from a wide variety of devices, operating
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+ systems, and partition types. There are also many options for customization
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+ such as graphical splash screens, playing sounds, mouse input, etc. The
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+ details of these options are beyond the scope of this introduction.</para>
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+
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+ <note><para>There is a command, <application>grub-mkconfig</application> that
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+ can write a configuration file automatically. It uses a set of scripts in
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+ /etc/grub.d/ and will destroy any customizations that you make. These scripts
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+ are designed primarily for non-source distributions and are not recommended for
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+ LFS. If you install a commercial Linux distribution, there is a good chance
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+ that this program will be run. Be sure to back up your grub.cfg file.</para></note>
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</sect2>
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Bruce Dubbs