Comment 7 for bug 66615

The Debian/Ubuntu run levels are as follows:

0 System Halt
1 Single user
2 Full multi-user mode (Default)
3-5 Same as 2
6 System Reboot

Thus, a correct /etc/event.d/svscan is as follows:
start on runlevel 2
start on runlevel 3
start on runlevel 4
start on runlevel 5

stop on runlevel 0
stop on runlevel 1
stop on runlevel 6

respawn
exec /usr/bin/svscanboot