Issue 1 May 2002 3-1 555-233-143
Initialization and Recovery
This chapter describes initialization and shutdown of the servers and the causes,
effects, and duration of each reset level used to restart the system. It includes the
following topics:
Initialization
After a server is powered on, the following software/firmware modules are
executed in the following order:
1. BIOS — The BIOS (Basic Input/Output System) takes control of the
server’s Pentium processor and provides several services including:
■ Running diagnostics on the server’s hardware (processor, memory,
disk, etc.).
■ Reading the 512-byte master boot record (MBR) from the boot
sector of the boot disk into memory and passing control to it. The
MBR contains phase 1 of the Linux loader (LILO).
2. LILO — The Linux loader (LILO) reads the Linux kernel from the boot disk
and transfers control to it. Phase 1 of LILO was read into memory by the
BIOS. When Phase 1 begins executing, it reads in the rest of the LILO
program, including the Linux kernel’s location. LILO reads in the Linux
kernel, uncompresses it, and transfers control to it.
3. Linux Kernel — The Linux kernel initializes the Pentium processor’s
registers, initializes its own data structures, determines the amount of
available memory, initializes the various compiled-in device drivers, etc.
When finished, the Linux kernel creates the first process, known as “init.”
4. Init — The init process creates the remaining processes for the system
using the
/etc/inittab file, which specifies “runlevels” and a set of
processes to run at each runlevel.
The “rc” script runs the service startup scripts in /etc/rc.d/rc4.d in
numeric order (S00* through S99*). Each of these startup scripts starts a
particular Linux service (e.g., inetd). In addition to starting up the various
services, the disk partitions are checked for sanity, and loadable modules
are loaded.
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