2.4.1 The init program

Like all Unices, Debian boots up by executing the program init. The configuration file for init (which is /etc/inittab) specifies that the first script to be executed should be /etc/init.d/rcS.

What happens next depends on whether the sysv-rc package or the file-rc package is installed. The following assumes that the sysv-rc package is installed. (file-rc contains its own /etc/init.d/rcS script and uses a file instead of symlinks in rc directories to control which services are started in which runlevels.)

The /etc/init.d/rcS file from the sysv-rc package runs all of the scripts in /etc/rcS.d/ in order to perform initialization such as checking and mounting file systems, loading modules, starting the network services, setting the clock, and so on. Then, for compatibility, it also runs all the files (except those with a `.' in the filename) in /etc/rc.boot/. The latter directory is reserved for system administrator use, and using it is deprecated. See System initialization, Section 9.1 and System run levels and init.d scripts in the Debian Policy Manual for more info.

Debian does not use a BSD-style rc.local directory.