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 using Lilo, which in the context of this book means x86_64 Pure64 systems. Information on “boot loading” for other architectures should be available in the usual resource-specific locations for those architectures.

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 “rescue” the computer if the computer becomes unusable (un-bootable).

If you have multiple systems on your machine using a different bootloader such as GRUB, you may prefer to use that instead - consult the appropriate documentation. The rest of this section assumes you are going to use Lilo.

Earlier, we compiled and installed the Lilo boot loader software in preparation for this step. The procedure involves writing a boot image to a specific location on the hard drive. We highly recommend using mkrescue to create a Lilo boot CD (using e.g. dvdrecord from dvdrtools) as a backup (this requires loopback block device support in the kernel).

Normally, you interact with Lilo by using the cursor and enter keys to select from the available option(s), but sometimes it is necessary to add other boot options, such as e.g. 'init=/bin/bash' to debug boot failures. The more your keyboard layout differs from the US qwerty layout, the harder it becomes to type boot options unless Lilo knows about your keyboard layout. So, we will create a key table for Lilo (.ktl) file - at one point in the documentation these are referred to as .klt files, which may be a typo, but has been followed by some distros. The name, and location, are not important but it is conventional to put these in /boot with the name representing the key layout. For a British keyboard layout, the following command will achieve this:

keytab-lilo.pl uk >/boot/uk.ktl

The argument to the command is the name of the keymap, or if necessary you can specify the full path to the keymap. Use whatever is appropriate for your keyboard.

When the x86 CLFS book used to include Lilo, it advised against running it from chroot in case the MBR became corrupted. Provided you have /proc mounted and have device special files for the disks, it seems to be safe to run recent versions of Lilo in chroot, although it is always possible that an updated bootloader, or defective configuration file, may render the system unbootable.

The next step is to create /etc/lilo.conf:

cat > /etc/lilo.conf << "EOF"
# Begin /etc/lilo.conf
# lilo.conf
#
# global options
boot=/dev/<bootdisk>
keytable=/boot/<keytable>
lba32
map=/boot/map
prompt

# set the name of the default image to boot
default=clfs

# define an image
image=/boot/clfskernel
    label=clfs
    root=/dev/<partition>
    read-only
# optionally add parameters to pass, e.g.
#   append="video=radeonfb:1024x768-16@70"

# repeat for any other kernel images

# optionally, add legacy operating systems
# see man lilo.conf for examples 
EOF

Replace <bootdisk> with the name of the disk (or partition) on which the boot sector is to be written, e.g. sda. Replace <keytable> with the name of the keytable file you created, and <partition> with the name of the root partition for the new system.

Run Lilo:

/sbin/lilo -v

If you are running multiple systems on this box and using Lilo, it is a good idea to ensure that each system is running the same version of Lilo, otherwise an old version may not be able to overwrite the bootloader from a newer version. You will also need to ensure that the copies of /etc/lilo.conf on each system are kept synchronised.