YMMV indeed. Here's the run-levels for a couple of different *n?x systems.

SuSE distro

System stop
S
Single user mode
1
Multiuser w/o network
2
Multiuser w/ network
3
Multiuser w/ network & X
4
Free
5
Free
6
Reboot
muLinux
System stop
S
Single user mode
1
Limbo level
2
Free
3
Free
4
Standard setup
5
Standard setup w/ server, daemons & X
6
Shutdown

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