Configuration of runlevels:

/etc/inittab

init q                               #Updates the inittab file without reboot!
id:5:initdefault:                    #Start in runlevel 5 als default

Start myprocess at runlevel 3:

5:3:once:/etc/myprocess

Problems with X after update or other problems. Solution: Add to /etc/inittab

x:5:respawn:/etc/X11/prefdm -nodaemon

Show runlevel:

runlevel

Change runlevel:

init value       #Value can be 1-6

Change runlevel on ubuntu:

telinit value

Shutdown:

init 6
shutdown -k +3 Please save your work now!
shutdown -r now

Example: Nagios NRPE Agent

#!/bin/sh
### BEGIN INIT INFO
# Provides: nrpe
# Required-Start: $networking
# Required-Stop: $networking
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Description: Nagios Remote Executor Plugin
### END INIT INFO

#####Variables#####
DIR="/usr/local/nagios/bin"


start() {
	echo "start nrpe"
	${DIR}/nrpe -c ${DIR}/nrpe.cfg -d -n
	ps ax --width=1000 | grep "${DIR}/nrpe" | cut -d " " -f1 | head -n 1 > /tmp/nrpe_process_count.txt
}
stop() {
	echo "stop nrpe" 
	nrpe_pid=`ps ax --width=1000 | grep "${DIR}/nrpe" | cut -d " " -f1 | head -n 1`
	kill $nrpe_pid
	rm /tmp/nrpe_process_count.txt
}

status() {

	if [ -f /tmp/nrpe_process_count.txt ]
	then
		read line < /tmp/nrpe_process_count.txt
		if [ $line -gt 0 ];
        	then
        	echo -n "nrpe ( pid "
        	ps ax --width=1000 | grep "${DIR}/nrpe" | cut -d " " -f1 | head -n 1
        	echo -n ") is running..."
		echo
		fi
	else
        echo "nrpe is stopped"
        fi
}

case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
#sleep 3
start
;;
status)
status
;;
*)
echo "Usage: nrpe {start|stop|restart|status}"
exit 1
esac

Example Tomcat:

Tomcat6

Enter the Grub-Shell with “e”, go to the very end of the line “linux”, change the “ro” to “rw” and add

init=/bin/bash

press enter, then press F10 to boot your system.

See also: https://help.ubuntu.com/community/LostPassword

Enter

init=/bin/bash

in grub-menu and boot (enter).