Red Hat ENTERPRISE LINUX 3 Reference Manual page 21

Chapter 1. Boot Process, Init, and Shutdown
If any problems occur using the SMP kernel, try selecting the a non-SMP kernel upon rebooting.
Once the second stage boot loader has determined which kernel to boot, it locates the corresponding
kernel binary in the
/boot/vmlinuz- kernel-version
nel version specified in the boot loader's settings).
For instructions on using the boot loader to supply command line arguments to the kernel, refer to
Chapter 2 Boot Loaders. For information on changing the runlevel at the GRUB or LILO prompt,
refer Section 2.10 Changing Runlevels at Boot Time.
The boot loader then places the appropriate initial RAM disk image, called an
The is used by the kernel to load drivers necessary to boot the system. This is particularly
initrd
important if SCSI hard drives are present or if the systems uses the ext3 file system
Warning
Do not remove the
will cause the system to fail with a kernel panic error message at boot time.
Once the kernel and the initrd image are loaded into memory, the boot loader hands control of the
boot process to the kernel.
For a more detailed overview of the GRUB and LILO boot loaders, refer to Chapter 2 Boot Loaders.
1.2.2.1. Boot Loaders for Other Architectures
Once the kernel loads and hands off the boot process to the
events occurs on every architecture. So the main difference between each architecture's boot process
is in the application used to find and load the kernel.
For example, the Alpha architecture uses the aboot boot loader, the Itanium architecture uses the
ELILO boot loader, IBM pSeries uses YABOOT, and IBM s390 systems use the z/IPL boot loader.
Consult the Red Hat Enterprise Linux Installation Guide specific to these platforms for information
on configuring their boot loaders.
1.2.3. The Kernel
When the kernel is loaded, it immediately initializes and configures the computer's memory and con-
figures the various hardware attached to the system, including all processors, I/O subsystems, and
storage devices. It then looks for the compressed
ory, decompresses it, mounts it, and loads all necessary drivers. Next, it initializes virtual devices
related to the file system, such as LVM or software RAID before unmounting the
and freeing up all the memory the disk image once occupied.
The kernel then creates a root device, mounts the root partition read-only, and frees any unused mem-
ory.
At this point, the kernel is loaded into memory and operational. However, since there are no user
applications that allow meaningful input to the system, not much can be done with the system.
2. For details on making an initrd, refer to the chapter titled The ext3 File System in the Red Hat Enterprise
Linux System Administration Guide.
directory. The kernel binary is named using the following format —
/boot/
directory from the file system for any reason. Removing this directory
/initrd/
file (where
kernel-version
init
image in a predetermined location in mem-
initrd
corresponds to the ker-
, into memory.
initrd
2
.
command, the same sequence of
initrd
3
disk image