Chapter 4. Configure the boot loader
When a PC boots the CPU it runs code from Read-Only Memory.
This code is the Basic Input/Output System, or
BIOS. The BIOS then loads a
boot loader from the Master Boot Record of the first hard
disk.
In turn, the boot loader reads the operating system into memory and
then runs it.
Neither the BIOS nor the boot loader are
strictly necessary. For example, there are versions of Linux
that run directly from the flash memory which usually contains the
BIOS. Linux was originally designed to run
without an interactive boot loader, by placing the kernel at
particular sectors of the disk.
The benefits of using a boot loader are:
Multiple operating systems can be booted. See the Linux + Windows HOWTO for
more information.
Parameters can be passed to the kernel interactively. This
is useful for solving hardware problems; for example, some
interrupt lines can be disabled, direct memory access to some
drives can be disabled, and so on. See the Linux
BootPrompt-HOWTO for a list of kernel
parameters.
Differing kernels can be interactively loaded. This is
useful when deploying a new kernel, as it provides simple fallback
to a proven kernel.
For these reasons systems administrators want to be able to
interactively control the boot loader from the serial
console.
LILO,
GRUB and
SYSLINUX are popular boot loaders for
IBM
PCs. Find which of these boot
loaders your Linux
installation uses and then follow the instructions for your boot
loader in the following section.