SuSE 8.0 Boot Process

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SuSE Boot Process

RC Scripts Explained:

 Explanation:

There are two kinds of symbolic link:
- start links, which are called when entering a run level, and
- stop links, which are called when leaving a run level.

Note that each service in the run levels 2, 3, 4, and 5 consists of a start and a stop link. Within SuSE boot concept a differential link scheme is used to be able to change a runlevel in comparision with the former level.

To avoid redundant starts when changing run levels only those services are started, which have no start link in the previous run level. And to avoid redundant stops when changing run levels, only those services are stopped which have no start link in the current level. To control this behaviour, the names of the scripts are added on the names of the start and stop links.

To control the order of service starts and stops, the start and stop links include a number in their link name.

The system configuration file /etc/rc.config contains most of the variables used to configure the installed services. These variables can easily be changed by YaST or by using an editor. After using an editor, the script /sbin/SuSEconfig must be called to distribute the settings into the system.

Secure Shell (SSH) Daemon Example:

The script /etc/init.d/sshd starts or stops the ssh daemon, according to the flag used:

   /etc/init.d/sshd start

and

   /etc/init.d/sshd stop

To do this automatically in run level 3, this script is linked into /etc/init.d/rc3.d/ with these two symbolic links

/etc/init.d/rc3.d/S20sshd -> ../sshd
and /etc/init.d/rc3.d/K20sshd -> ../sshd

The corresponding link with the letter S is used to start a service. For the printing service the number between the letter S and the name should be greater than the number of the start link of the network service. The corresponding link with the letter K is used to stop a service. The number of the stop link should be less than that of the stop link for the network service so that the ssh daemon is stopped before shutting down the network service.
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