Firstly, the runlevels.
| ID | Name | Description |
|---|---|---|
| 0 | Halt | Shuts down the system. |
| 1 | Single-user mode | Mode for administrative tasks. |
| 2 | Multi-user mode | Does not configure network interfaces and does not export networks services. |
| 3 | Multi-user mode with networking | Starts the system normally. |
| 4 | Not used/user-definable | For special purposes. |
| 5 | Start the system normally with appropriate display manager (with GUI) | Same as runlevel 3 + display manager. |
| 6 | Reboot | Reboots the system. |
sudo apt-get install sysv-rc-conf
sysv-rc-conf a nice text based tool to on/off the process runlevel.
