Switching Runlevels Manually

If you want to switch runlevels, you can use the i nit or telinit commands, which are located in the /sbin directory on SUSE systems. The telinit command is a symbolic link to the i nit command. The i nit command behaves slightly differently when invoked as telinit, taking the -t flag followed by an integer number of seconds. The i nit command will wait the specified number of seconds before switching to the specified runlevel.

The i nit process is fondly referred to as the grandfather process on Unix and Linux systems, as it is the first process started by the kernel after the kernel has finished initializing and is the process that controls the startup of all processes on the system. The init process always has process ID number 1 and always exists on a Linux system. It is impossible to kill the i nit process.

When i nit is executed by the kernel, it reads the system's default runlevel from the file /etc/inittab. The entry for the system's default runlevel in this file looks like the following:

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