Novell LINUX ENTERPRISE SERVER 11 - ADMINISTRATION Administration Manual page 82

Generally, two things happen when you change runlevels. First, stop scripts of the
current runlevel are launched, closing down some programs essential for the current
runlevel. Then start scripts of the new runlevel are started. Here, in most cases, a number
of programs are started. For example, the following occurs when changing from runlevel
3 to 5:
1. The administrator (root) requests init to change to a different runlevel by entering
telinit 5.
2. init checks the current runlevel (runlevel) and determines it should start /etc/
init.d/rc with the new runlevel as a parameter.
3. Now rc calls the stop scripts of the current runlevel for which there is no start
script in the new runlevel. In this example, these are all the scripts that reside in
/etc/init.d/rc3.d (old runlevel was 3) and start with a K. The number
following K specifies the order to run the scripts with the stop parameter, because
there are some dependencies to consider.
4. The last things to start are the start scripts of the new runlevel. In this example,
these are in /etc/init.d/rc5.d and begin with an S. Again, the number that
follows the S determines the sequence in which the scripts are started.
When changing into the same runlevel as the current runlevel, init only checks /etc/
inittab for changes and starts the appropriate steps, for example, for starting a
getty on another interface. The same functionality may be achieved with the command
telinit q.
7.2.2 Init Scripts
There are two types of scripts in /etc/init.d:
Scripts Executed Directly by init
This is the case only during the boot process or if an immediate system shutdown
is initiated (power failure or a user pressing Ctrl + Alt + Del ). For IBM System z
systems, this is the case only during the boot process or if an immediate system
shutdown is initiated (power failure or via "signal quiesce"). The execution of these
scripts is defined in /etc/inittab.
68 Administration Guide