From HowTo: Speed up ubuntu boot process.
sudo sysv-rc-conf
Throw a littel bit of runlevel knowledge here before we start messing them up.... All the boot processes are executed in sequence as following:
runlevel S: the first runlevel in boot process. /etc/init.d/rcS script will be invoked to start and all the processes underneath /etc/rcS.d will be executed.
runlevel 1: the single user mode. All processes underneath /etc/rc1.d will be executed.
runlevel 2,3,4,5: in debain system, the multi-user env, may not may not include GUI. The same, processes under each of the corresponding dirs will be run. **Note** this is different than RedHat, SuSE, and other RPM based systems.
runlevel 0: computer shutdown.
runlevel 6: computer reboot.
