Runit is an init system replacement with service supervision. Although it is not usable out of the box, it can be easily managed to do so.
Runit starts as the number one process. After that it runs /etc/runit/1, 2 and 3 initialisation scripts, also called "stages". You can redefine them. Stage 1 is meant for essential startup tasks, which are handled by old initscripts. Stage 2 is for normal boot process It calls runsv(8) on /service directory, where runit services are located. A runit service looks like a directory with two executable scripts: run and finish. There is also a supervision directory, where PID files and logs are located. Yes, you do not have to use syslogd. A valid runit run script should execute a daemon; the daemon being executed should stay in foreground. If that daemon exits, it will be restarted by runit. A finish script is not necessary, however you can define it.
How to make it simply work
# apt-get install runit mkdir /etc/runit cp -rf /usr/share/doc/runit/debian/* /etc/runit/* mkdir /service ln -s /etc/sv/getty-5/ /service/getty-5
After youll boot with runit as PID 1 (you should add init=/sbin/runit-init to your kernel command line) youll have a getty at tty5. To add a runit entry to the GRUB menu, add /sbin/runit-init to the /etc/grub.d/10_linux file under the SUPPORTED_INITS string. You can add more initscripts into your /service directory. Gerrit Pape has a collection of these at http://smarden.org/runit/runscripts.html My pick is acpid,cups,dbus and slim.
If you need a run-once service and it is a dependency, you can try this: touch <service>/down an then call runsv o <service> from another init script
While using runit, you can`t shut down your system using shutdown(8) or telinit. That`s because runit does not listen to /run/initctl. You can use runit-init 0 or runit-init 6 for that. Here`s a small workaround for listening /run/initctl and calling runit for shutting down: http://pastebin.ca/3042417 To make it work, compile it with inireq.h file from original sysvinit sources and wrap it in a runit initscript.