0 Booting And Configuring A Linux System; The Linux Boot Process - Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual

Booting and Configuring a
Linux System
Booting a Linux system involves various different components. The hardware itself is
initialized by the BIOS, which starts the kernel by means of a boot loader. After this
point, the boot process with init and the runlevels is completely controlled by the oper-
ating system. The runlevel concept enables you to maintain setups for everyday usage
as well as to perform maintenance tasks on the system.

20.1 The Linux Boot Process

The Linux boot process consists of several stages each represented by another compo-
nent. The following list briefly summarizes the boot process and features all the major
components involved.
1. BIOS After the computer has been turned on, the BIOS initializes the screen
and keyboard and tests the main memory. Up to this stage, the machine does not
access any mass storage media. Subsequently, the information about the current
date, time, and the most important peripherals are loaded from the CMOS values.
When the first hard disk and its geometry are recognized, the system control passes
from the BIOS to the boot loader. If the BIOS supports network booting, it is also
possible to configure a boot server that provides the boot loader. On x86 systems,
PXE boot is needed. Other architectures commonly use the BOOTP protocol to
get the boot loader.
2. Boot Loader
loaded into the main memory and the boot loader that resides at the beginning of
this sector takes over. The commands executed by the boot loader determine the
The first physical 512-byte data sector of the first hard disk is
Booting and Configuring a Linux System
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