Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual page 409

memory. initramfs must always provide an executable named init that should execute
the actual init program on the root file system for the boot process to proceed.
Before the root file system can be mounted and the operating system can be started,
the kernel needs the corresponding drivers to access the device on which the root file
system is located. These drivers may include special drivers for certain kinds of hard
drives or even network drivers to access a network file system. The needed modules
for the root file system may be loaded by init on initramfs. After the modules are loaded,
udev provides the initramfs with the needed devices. Later in the boot process, after
changing the root file system, it is necessary to regenerate the devices. This is done by
boot.udev with the command udevtrigger.
If you need to change hardware (e.g. hard disks) in an installed system and this hardware
requires different drivers to be present in the kernel at boot time, you must update the
initramfs file. This is done in the same way as with its predecessor, initrd—by
calling mkinitrd. Calling mkinitrd without any argument creates an initramfs.
Calling mkinitrd -R creates an initrd. In SUSE Linux Enterprise®, the modules to
load are specified by the variable INITRD_MODULES in /etc/sysconfig/
kernel. After installation, this variable is automatically set to the correct value. The
modules are loaded in exactly the order in which they appear in INITRD_MODULES.
This is only important if you rely on the correct setting of the device files /dev/sd?.
However, in current systems you also may use the device files below /dev/disk/
that are sorted in several subdirectories, named by-id, by-path and by-uuid, and
always represent the same disk. This is also possible at install time by specifying the
respective mount option.
IMPORTANT: Updating initramfs or initrd
The boot loader loads initramfs or initrd in the same way as the kernel. It is
not necessary to reinstall GRUB after updating initramfs or initrd, because GRUB
searches the directory for the right file when booting.
20.1.2 init on initramfs
The main purpose of init on initramfs is to prepare the mounting of and access to the
real root file system. Depending on your system configuration, init is responsible for
the following tasks.
Booting and Configuring a Linux System 391