source: chapter06/grub-cfg.xml@ b2ae446

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>

<sect1 id="ch-bootable-temp" role="wrap">
  <?dbhtml filename="grub-cfg.html"?>

  <sect1info condition="script">
    <productname>grub</productname>
    <productnumber>&grub-version;</productnumber>
    <address>&grub-url;</address>
  </sect1info>

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

  <sect2>
    <title>Introduction</title>

    <para>In a normal LFS building procedure, we will chroot into the
    temporary system and continue to build additional temporary tools.
    But, as we've explained, in the Cross Edition we need to make the
    temporary system bootable and boot it on the target system.</para>
  </sect2>

  <sect2>
    <title>Creating the GRUB Configuration File</title>

    <para>Generate <filename>$LFS/boot/grub/grub.cfg</filename>:</para>

<screen><userinput>mkdir -pv $LFS/boot/grub
cat &gt; $LFS/boot/grub/grub.cfg &lt;&lt; "EOF"
<literal># Begin /boot/grub/grub.cfg
set default=0
set timeout=5

menuentry "LFS Temporary System" {
        linux   /vmlinux root=/dev/sda3 rw init=/bin/bash
        boot
}</literal>
EOF</userinput></screen>

    <variablelist>
      <title>The meaning of the linux command options:</title>

      <varlistentry>
        <term><parameter>root=/dev/sda3</parameter></term>
        <listitem>
          <para>We will use the third parition as the partition for the
          root filesystem of the LFS system.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>rw</parameter></term>
        <listitem>
          <para>Tell the kernel to mount the root filesystem read-write.
          In normal distros there is <parameter>ro</parameter> instead, so
          the kernel will mount the root filesystem read-only.  Then
          the <command>init</command> process can check the filesystem
          integrity and remount it read-write.  For the temporary system
          it's not needed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>init=/bin/bash</parameter></term>
        <listitem>
          <para>By default the kernel runs <command>/sbin/init</command>
          as the first process.  It's provided by SysVinit or Systemd
          package, which is not installed yet.  We explicitly tell the
          kernel to run <command>/bin/bash</command> instead to start a
          shell, so we can run further commands interactively.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>(optional) <parameter>console=ttyS0,115200</parameter></term>
        <listitem>
          <para>Use the serial port at <filename>/dev/ttyS0</filename> as
          the output console device.  It's very useful if the virtual
          console is not avaliable (for example, the target system may lack
          graphic output, or the framebuffer console may be too slow).
          And, by connecting the host system and the target system with a
          NULL modem or USB serial converter, it will be able to copy the
          commands from the book and paste it into a terminal emulator
          (for example,
          <ulink url='&blfs-book;general/screen.html'>GNU Screen</ulink>)
          on the host, to execute them on the target system.
          <parameter>115200</parameter> specifies the baudrate, the default
          (9600) is too slow for large amount of console output building
          LFS.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <note><para>From <application>GRUB</application>'s perspective, the
    kernel files are relative to the partition used.  We will use a
    a separate /boot partition, so /boot is not needed in the above
    <emphasis>linux</emphasis> line.
    </para></note>

   </sect2>

   <sect2>
     <title>Copy the Temporary System to the Target Machine</title>

     <note>
       <para>The commands in the subsection must be performed on the host
       system while logged in as user
       <systemitem class="username">root</systemitem>
       and no longer as user <systemitem class="username">lfs</systemitem>.
       Also, double check that <envar>$LFS</envar> is set in <systemitem
       class="username">root</systemitem>'s environment.</para>
     </note>

     <para>Now it's the time to copy the
     <filename class="directory">$LFS</filename> hierarchy over to your
     target machine.  You'll need a <quote>moveable</quote> device for this.
     Using a normal USB stick is likely a bad choice: the USB sticks are
     generally not optimized for reading or writing many small files
     (which will happen building packages from source). Especially, if a
     ext filesystem is used, the performance can be very bad.  You may use
     a USB to SATA adapter and a HDD or SSD (then you can directly connect
     it onto the SATA port of the target system, or continuing to use the
     adapter on a USB port of the target system), or a USB stick with an I/O
     controller for SSD (these USB sticks are significantly more expansive
     than a normal one).</para>

     <para>Create a GUID partition table on the device, and then create
         three partitions on it. The first will be used as the BIOS boot
     partition, 1 MB is sufficient enough.  But if you want to use EFI to
     boot your LFS system later, assign 100 MB for it so it will be possible
     to convert it into an EFI system partition. The second partition will
     be used as the boot partition, 500 MB is sufficient enough.  The third
     will be the root partition, it should be at least 20 GB.</para>

     <para>Create filesystems for the partitions:</para>

<screen><userinput role='nodump'>mkfs.ext4 /dev/<replaceable>sdx</replaceable>2
mkfs.ext4 /dev/<replaceable>sdx</replaceable>3</userinput></screen>

     <para>
       It's not needed to create a filesystem for the BIOS boot partition.
       But, its type should be set to <quote>BIOS boot</quote> in
       the partition table using <command>fdisk</command>:
     </para>

<screen role="nodump"><userinput>fdisk /dev/<replaceable>sdx</replaceable></userinput>
<literal>
Welcome to fdisk (util-linux &util-linux-version;).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): </literal><userinput>t</userinput>
<literal>Partition number (1-9, default 9): </literal><userinput>1</userinput>
<literal>Partition type or alias (type L to list all): </literal><userinput>BIOS boot</userinput>
<literal>Changed type of partition 'Linux' to 'BIOS boot'.

Command (m for help): </literal><userinput>w</userinput>
<literal>The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.</literal></screen>

     <para>In <xref linkend="ch-tools-cleanup"/> it's optional to make a
     backup for the temporary system.  If you'd like to do so, prepare
     another parition (1 GB should be enough) and make an
     <systemitem class="filesystem">ext4</systemitem> filesystem to hold
     the backup:</para>

<screen><userinput role='nodump'>mkfs.ext4 /dev/<replaceable>sdx4</replaceable></userinput></screen>

     <para><replaceable>sdx</replaceable> should be replaced with the name
     of the device node corresponding to your moveable device. Then mount
     the filesystems:</para>

<screen><userinput role='nodump'>mkdir -pv /mnt/lfs-target
mount -v -t ext4 /dev/<replaceable>sdx</replaceable>3 /mnt/lfs-target
mkdir -pv /mnt/lfs-target/boot
mount -v -t ext4 /dev/<replaceable>sdx</replaceable>2 /mnt/lfs-target/boot</userinput></screen>

     <para>Copy the temporary system onto the device, and change the
     ownership of the copy to user
     <systemitem class="username">root</systemitem>:</para>

<screen><userinput role='nodump'>cp -av $LFS/* /mnt/lfs-target
chown -R root:root /mnt/lfs-target</userinput></screen>

     <para>Install the bootloader onto the device:</para>

<screen><userinput role='nodump'>$LFS/tools/sbin/lfs-grub-install          \
    --target=i386-pc                      \
    --boot-directory=/mnt/lfs-target/boot \
    /dev/<replaceable>sdx</replaceable></userinput></screen>

     <para>Create the mountpoint for
     <systemitem class="filesystem">devtmpfs</systemitem>, so the kernel
     will mount it automatically:</para>

<screen><userinput role='nodump'>install -v -dm755 /mnt/lfs-target/dev</userinput></screen>

     <para>Now, unmount the device:</para>

<screen><userinput role='nodump'>umount -Rv /mnt/lfs-target</userinput></screen>

     <para>Now unplug the device and connect it onto the target system,
     and boot the target system with this device as the boot device.
     Read the manual from the vendor of the target system to know how to
     select the boot device.</para>

  </sect2>

</sect1>