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Unit 4: Configuring Desktop

interfaces to programs that provide the ability to configure and customize the system. Every notes
function you perform via an applet in the menu can also be done via commands. In fact, in many
instances, the commands offer additional options that haven’t yet migrated to the graphical
applets.
Desktop control centre

Key features
Extreme performance, full control
1. Overclock CPU, memory, and bus speeds for optimal performance
2. Integrated auto-tuning makes system optimization easy while maintaining system
stability
4.2 understanding the run Levels

If you’re one of those who took a chance and got one of the Caldera Previews or got a Red Hat
distribution on your system, one of your original thoughts may have been the same as mine:
What happened to /etc/rc.local? Where am I supposed to put my custom commands? [One
answer: /etc/rc.d/rc.local is available on Red Hat systems—ED] What if I don’t want the HTTP
server to start?
For those of you out there who administer Sun Solaris machines, this looks quite familiar. But
I was just scratching my head for a while until I wound up administering a system, and it all
became clear. Time to share the knowledge.
The idea behind the setup is to make everything script-based. For each run level, scripts are run
to start each individual service, instead of having a few large files to edit by hand. These scripts
are located in /etc/rc.d/init.d, and most take as an option start or stop. This is to allow the
specific programs to start (on bootup) or stop (on shutdown).

This setup involves a bunch of directories under /etc/rc.d/. These are:
rc0.d Contains scripts to run when the system shuts down. Technically, halt or shutdown bring
the system to runlevel 0. This directory is mostly made up of kill commands.

rc1.d through rc3.d Scripts to run when the system changes runlevels. Runlevel 1 is usually single-
user mode, runlevel 2 is for multi-user setup without NFS, and runlevel 3 is full multi-user and
networking.

Runlevel 4 is typically unused.
rc5.d Scripts to start the system in X11 mode. This is the same as runlevel 3, with the exception
that the xdm program starts, which provides a graphical login screen.
rc6.d Scripts to run when the system reboots. These scripts are called by a reboot command.

init.d Actually contains all of the scripts. The files in the rc?.d directories are really links to the
scripts in the init.d directory.

the Boot sequence

Now that we know where files are located, let’s look at what happens in a normal Red Hat boot
sequence.
Once the system boots, /etc/rc.d/rc.sysinit is run first. The starting runlevel (specified in /etc/
inittab) is found, and the /etc/rc.d/rc script is run, with the sole option being the runlevel we
want to go to. For most startups, this is runlevel 3.

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