Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 11-05-2007, Руководство по установке

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19
Booting and Configuring a
Linux System
Booting a Linux system involves various different components. Started by the BIOS,
the boot loader runs the kernel and some drivers that are necessary for booting. After
this, the behavior of the computer strongly depends on init and the configuration of the
runlevel used.
19.1 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 The first physical 512-byte data sector of the first hard disk is
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
remaining part of the boot process. Therefore, the first 512 bytes on the first hard
Booting and Configuring a Linux System 371