Linux Runlevels

Linux Standard Base specification

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 )	As runlevel 3 + display manager.
6	Reboot	Reboots the system.

Debian GNU/Linux

ID	Description
S	Only run on boot (replaces /etc/rc.boot)
0	Halt
1	Single-user mode
2-5	Full Multi-user with console logins and display manager if installed
6	Reboot

Red Hat Linux and Fedora

Code	Information
0	Halt
1	Single-user mode
2	Multi-user mode console logins only (without networking)
3	Multi-user mode, console logins only
4	Not used/User-definable
5	Multi-user mode, with display manager as well as console logins (X11)
6	Reboot

SUSE Linux

ID	Description
0	Halt
1 or S	Single-user mode
2	Multi-user mode without networking
3	Multi-user mode, console logins only
4	Not used/User-definable
5	Multi-user mode with display manager
6	Reboot

Slackware Linux

ID	Description
0	Halt
1	Single-user mode
2	Unused but configured the same as runlevel 3
3	Multi-user mode without display manager
4	Multi-user mode with display manager
5	Unused but configured the same as runlevel 3
6	Reboot

Arch Linux

ID	Description
0	Halt
1	Single-user (Maintenance Mode)
2	Not used
3	Multi-user
4	Not used
5	Multi-user with X11
6	Reboot

Gentoo Linux

ID	Description
0	Halt
1 or S	Single-user mode
2	Multi-user mode without networking
3	Multi-user mode
4	Aliased for runlevel 3
5	Aliased for runlevel 3
6	Reboot

Unix:

System V Releases 3 and 4

ID	Description
0	Shut down system, power-off if hardware supports it (only available from the console)
1	Single-user mode, all filesystems unmounted but root, all processes except console processes killed
2	Multi-user mode
3	Multi-user mode with RFS (and NFS in Release 4) filesystems exported
4	Multi-user, User-definable
5	Halt the operating system, go to firmware
6	Reboot
s, S	Identical to 1, except current terminal acts as the system console

Solaris

ID	Description
0	Operating system halted; (SPARC only) drop to OpenBoot prompt
S	Single-user mode with only root filesystem mounted (as read-only) -- Solaris 10+: svc:/milestone/single-user
1	Single-user mode with all local filesystems mounted (read-write)
2	Multi-user mode with most daemons started – Solaris 10+: svc:/milestone/multi-user
3	Multi-user mode; identical to 2 (runlevel 3 runs both /sbin/rc2 and /sbin/rc3), with filesystems exported, plus some other network services started. -- Solaris 10+: svc:/milestone/multi-user-server
4	Alternative Multi-user mode, User-definable
5	Shut down, power-off if hardware supports it
6	Reboot

HP-UX

ID	Description
0	System halted
S	Single-user mode, booted to system console only, with only root filesystem mounted (as read-only)
s	Single-user mode, identical to S except the current terminal acts as the system console
1	Single-user mode with local filesystems mounted (read-write)
2	Multi-user mode with most daemons started and Common Desktop Environment launched
3	Identical to runlevel 2 with NFS exported
4	Multi-user mode with VUE started instead of CDE
5, 6	Not used/User-definable

AIX

ID	Name	Description
0		reserved
1		reserved
2	Normal Multi-user mode	default mode