update-rc.d - install and remove System-V style init script links
[SYNOPSIS] update-rc.d OPTION SERVICE ACTION
action
defaults make links to start the service in runlevels 2345 and to stop the service in runlevels 016
# update-rc.d sshd defaults
remove remove all links to start the service
# update-rc.d sshd remove

option
-n Don't do anything, just show what we would do
-f Force removal of symlinks