From: Petter Reinholdtsen
Single user mode is defined like this in /etc/inittab: "~~:S:wait:/sbin/sulogin". This means the only thing that is -executed in single user mode in sulogin. Single user mode is a boot +executed in single user mode is sulogin. Single user mode is a boot state "between" the runlevels, and when booting into single user mode, only the scripts in /etc/rcS.d/ are executed before the init process enters the single user state. When switching to runlevel 1, the state