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

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Loading the Installation System or Rescue System
As soon as the hardware has been properly recognized, the appropriate drivers have
been loaded, and udev has created the device special files, init starts the installation
system, which contains the actual YaST installer, or the rescue system.
Starting YaST
Finally, init starts YaST, which starts package installation and system configuration.
19.2 The init Process
The program init is the process with process ID 1. It is responsible for initializing the
system in the required way. init is started directly by the kernel and resists signal 9,
which normally kills processes. All other programs are either started directly by init or
by one of its child processes.
init is centrally configured in the
/etc/inittab
file where the runlevels are defined
(see Section 19.2.1, “Runlevels” (page 375)). The file also specifies which services and
daemons are available in each of the levels. Depending on the entries in
/etc/
inittab
, several scripts are run by init. For reasons of clarity, these scripts, called
init scripts, all reside in the directory
/etc/init.d
(see Section 19.2.2, “Init Scripts”
(page 378)).
The entire process of starting the system and shutting it down is maintained by init.
From this point of view, the kernel can be considered a background process whose task
is to maintain all other processes and adjust CPU time and hardware access according
to requests from other programs.
19.2.1 Runlevels
In Linux, runlevels define how the system is started and what services are available in
the running system. After booting, the system starts as defined in
/etc/inittab
in
the line
initdefault
. Usually this is
3
or
5
. See Table 19.1, “Available Runlevels”
(page 376). As an alternative, the runlevel can be specified at boot time (by adding the
runlevel number at the boot prompt, for instance). Any parameters that are not directly
evaluated by the kernel itself are passed to init.
Booting and Configuring a Linux System 375