source: BOOK/bootable/x86/grub.xml@ 1c78387

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

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

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

  <para os="a">Your shiny new CLFS 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 os="b">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 os="c">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 os="d"><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 os="e">Remove the diskette and store it somewhere safe. Now, run the
  <command>grub</command> shell:</para>

<screen os="f"><userinput>grub</userinput></screen>

  <para os="g">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 os="h">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 os="i">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 os="j"><userinput>root (hd0,3)</userinput></screen>

  <warning os="k">
    <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 CLFS partition. In this case, this
    next command would become <userinput>setup (hd0,3)</userinput>.</para>
  </warning>

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

<screen os="m"><userinput>setup (hd0)</userinput></screen>

  <para os="n">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 os="o"><userinput>quit</userinput></screen>

  <para os="p">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 CLFS.
title CLFS &version;
root (hd0,3)
kernel /boot/clfskernel-&linux-version; root=/dev/hda4</literal>
EOF</userinput></screen>


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

<screen os="r"><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 os="s">If dual-booting Windows, the following entry will allow
  booting it:</para>

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

  <para os="u">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 os="v">The FHS stipulates that the bootloader's configuration file should
  be symlinked to <filename class="symlink">/etc/{Bootloader Name}</filename>.
  To satisfy this requirement for GRUB, issue the following command:</para>

<screen os="w"><userinput>mkdir -v /etc/grub &amp;&amp;
ln -sv /boot/grub/menu.lst /etc/grub</userinput></screen>

</sect1>