Debian/sysvinit init script system quirks


Runlevel S does not run scripts. /etc/init.d/rcS runs them at system startup time (i.e. it is run by init)
Runlevels 0 and 6 (halt/reboot) are handled differently:
Init scripts always called with "stop" action
/etc/rcS.d/ (startup) scripts ending in .sh are sourced
Runlevel change tries to optimize start/stop
If the init script ordering is not well designed then bugs appear

Debian:
Does not try to take proper care of the ordering of init scripts
Has a big number of init scripts in the default "20" order number
Many border conditions are defined and explained in policy