Information Technology Reference
In-Depth Information
Boot Programs
: In this phase,
bootblk
loads the
ufsboot
program into
memory and executes it.
➤
Kernel Initialization
: In this phase, the
ufsboot
program loads the
core kernel into memory and causes it to execute. The kernel initializes
its data structures and begins loading other kernel modules on the basis
of the
/etc/system
file using the
ufsboot
program. After all the neces-
sary modules are loaded and initialized, the kernel starts the
/sbin/init
program.
➤
init
: In this phase, the
init
program starts other processes on the basis of
the information contained in the
/etc/inittab
file. These include a pro-
gram that calls the run control (rc) scripts that set up various system services.
➤
Kernel Modules
Kernel software is divided into groups of related functions referred to as
mod-
ules
. Some modules are part of a small, common core of the operating system.
Some modules provide platform-specific operations, whereas other modules are
device drivers. This architecture allows portions of the kernel to be included or
excluded on the basis of the desired functionality or allows portions of the ker-
nel to be updated without replacing the entire kernel. The device drivers are
dynamic kernel modules that are loaded when the device is accessed.
The kernel modules are stored in three directories—two under the root file
system and one under the
/usr
file system:
/platform/sun4c/kernel
for sun4c platforms—This directory is used for
modules that are specific to the platform.
➤
/kernel—
This directory is used for common kernel modules required for
booting.
➤
/usr/kernel
—This directory is used for common kernel modules used by
platforms with a particular instruction set.
➤
The
/etc/system
file is used to determine which kernel modules are loaded
and to define various kernel parameters. The format of this file takes the form
of one or more keywords followed by one or more parameters. The support-
ed keywords are as follows:
exclude
—Prevents modules from loading
➤
forceload
—Forces a module to load
➤
moddir
—Changes the common kernel module directories
➤
