lfs-book/chapter08/grub.xml

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<sect1 id="ch-bootable-grub">
  <?dbhtml filename="grub.html"?>

  <title>Making the LFS System Bootable</title>

  <indexterm zone="ch-bootable-grub">
    <primary sortas="a-Grub">GRUB</primary>
    <secondary>configuring</secondary>
  </indexterm>

  <para>Your shiny new LFS system is almost complete. One of the last
  things to do is to ensure that the system can be properly booted. The
  instructions below apply only to computers of IA-32 architecture,
  meaning mainstream PCs. Information on <quote>boot loading</quote> for
  other architectures should be available in the usual resource-specific
  locations for those architectures.</para>

  <para>Boot loading can be a complex area, so a few cautionary
  words are in order. Be familiar with the current boot loader and any other
  operating systems present on the hard drive(s) that need to be
  bootable. Make sure that an emergency boot disk is ready to
  <quote>rescue</quote> the computer if the computer becomes
  unusable (un-bootable).</para>

  <para>Earlier, we compiled and installed the GRUB boot loader software
  in preparation for this step. The procedure involves writing some
  special GRUB files to specific locations on the hard drive. We highly
  recommend creating a GRUB boot floppy diskette as a backup. Insert a
  blank floppy diskette and run the following commands:</para>

<screen><userinput>dd if=/boot/grub/stage1 of=/dev/fd0 bs=512 count=1
dd if=/boot/grub/stage2 of=/dev/fd0 bs=512 seek=1</userinput></screen>

  <para>Remove the diskette and store it somewhere safe. Now, run the
  <command>grub</command> shell:</para>

<screen><userinput>grub</userinput></screen>

  <para>GRUB uses its own naming structure for drives and partitions in
  the form of <emphasis>(hdn,m)</emphasis>, where <emphasis>n</emphasis>
  is the hard drive number and <emphasis>m</emphasis> is the partition
  number, both starting from zero. For example, partition <filename
  class="partition">hda1</filename> is <emphasis>(hd0,0)</emphasis> to
  GRUB and <filename class="partition">hdb3</filename> is
  <emphasis>(hd1,2)</emphasis>. In contrast to Linux, GRUB does not
  consider CD-ROM drives to be hard drives. For example, if using a CD
  on <filename class="partition">hdb</filename> and a second hard drive
  on <filename class="partition">hdc</filename>, that second hard drive
  would still be <emphasis>(hd1)</emphasis>.</para>

  <para>Using the above information, determine the appropriate
  designator for the root partition (or boot partition, if a separate
  one is used). For the following example, it is assumed that the root
  (or separate boot) partition is <filename
  class="partition">hda4</filename>.</para>

  <para>Tell GRUB where to search for its
  <filename>stage{1,2}</filename> files. The Tab key can be used
  everywhere to make GRUB show the alternatives:</para>

<screen><userinput>root (hd0,3)</userinput></screen>

  <warning>
    <para>The following command will overwrite the current boot loader. Do not
    run the command if this is not desired, for example, if using a third party
    boot manager to manage the Master Boot Record (MBR). In this scenario, it
    would make more sense to install GRUB into the <quote>boot sector</quote>
    of the LFS partition. In this case, this next command would become
    <userinput>setup (hd0,3)</userinput>.</para>
  </warning>

  <para>Tell GRUB to install itself into the MBR of
  <filename class="partition">hda</filename>:</para>

<screen><userinput>setup (hd0)</userinput></screen>

  <para>If all went well, GRUB will have reported finding its files in
  <filename class="directory">/boot/grub</filename>. That's all there is
  to it. Quit the <command>grub</command> shell:</para>

<screen><userinput>quit</userinput></screen>

  <para>Create a <quote>menu list</quote> file defining GRUB's boot menu:</para>

<screen><userinput>cat &gt; /boot/grub/menu.lst &lt;&lt; "EOF"
<literal># Begin /boot/grub/menu.lst

# By default boot the first menu entry.
default 0

# Allow 30 seconds before booting the default.
timeout 30

# Use prettier colors.
color green/black light-green/black

# The first entry is for LFS.
title LFS &version;
root (hd0,3)
kernel /boot/lfskernel-&linux-version; root=/dev/hda4</literal>
EOF</userinput></screen>

  <para>Add an entry for the host distribution if desired. It might look
  like this:</para>

<screen><userinput>cat &gt;&gt; /boot/grub/menu.lst &lt;&lt; "EOF"
<literal>title Red Hat
root (hd0,2)
kernel /boot/kernel-2.6.5 root=/dev/hda3
initrd /boot/initrd-2.6.5</literal>
EOF</userinput></screen>

  <para>If dual-booting Windows, the following entry will allow
  booting it:</para>

<screen><userinput>cat &gt;&gt; /boot/grub/menu.lst &lt;&lt; "EOF"
<literal>title Windows
rootnoverify (hd0,0)
chainloader +1</literal>
EOF</userinput></screen>

  <para>If <command>info grub</command> does not provide all necessary material,
  additional information regarding GRUB is located on its website at:
  <ulink url="http://www.gnu.org/software/grub/"/>.</para>

  <para>The FHS stipulates that GRUB's <filename>menu.lst</filename> file should
  be symlinked to <filename class="symlink">/etc/grub/menu.lst</filename>. To
  satisfy this requirement, issue the following command:</para>

<screen><userinput>mkdir -v /etc/grub
ln -sv /boot/grub/menu.lst /etc/grub</userinput></screen>

</sect1>