RadHat / CentOs
0 — Halt
1 — Single-user text mode
2 — Not used (user-definable)
3 — Full multi-user text mode
4 — Not used (user-definable)
5 — Full multi-user graphical mode (with an X-based login screen)
6 — Reboot
Debian / Ubuntu
0 — Halt
1 — Single-user text mode
2 — Full multi-user graphical mode (with an X-based login screen)
3 — Not used (user-definable)
4 — Not used (user-definable)
5 — Not used (user-definable)
6 — Reboot
Suse
0 — Halt
1 — Single-user text mode
2 — Local multiuser mode without remote network (e.g., NFS)
3 — Full multiuser mode with network
4 — Not used (user-definable)
5 — Full multi-user graphical mode (with an X-based login screen)
6 — Reboot