csh -cf '/command/svscanboot &'at the end of /etc/rc.local.
Portability: This is the traditional approach.
SV:12345:respawn:/command/svscanbootat the end of /etc/inittab.
Portability: This is the traditional System V approach, and was almost universally supported among Linux systems for years, but was broken by Ubuntu 6.10.
start on runlevel-1 start on runlevel-2 start on runlevel-3 start on runlevel-4 start on runlevel-5 respawn /command/svscanbootinto /etc/event.d/svscan.
Portability: This worked under Ubuntu 6.10 but was broken by Ubuntu 7.04.
start on runlevel 1 start on runlevel 2 start on runlevel 3 start on runlevel 4 start on runlevel 5 respawn exec /command/svscanbootinto /etc/event.d/svscan.
Portability: This worked under Ubuntu 7.04 through 9.04 but was broken by Ubuntu 9.10.
start on runlevel  stop on runlevel [^12345] respawn exec /command/svscanbootinto /etc/init/svscan.conf.
Portability: This works under Ubuntu 9.10 through (at least) 11.10.