runlevels 7-9?

jimmy page · 01-08-2010, 11:54 AM

i was reading the man page for init and noticed the following sentence:

Quote:

"Runlevels 7-9 are also valid, though not really documented. This is because "traditional" Unix variants don't use them."

that brings up quite a few questions, first of all, what do they mean by "traditional" Unix? i suppose it means all unixes based off system V or something, am i right? are the BSDs traditional unixes? what happens if i manually switch to any of those runlevels?
i imagine they served a purpose originally, and are kept for historical reasons, wonder what they did though?

i'm just curious, no big deal.

macemoneta · 01-08-2010, 12:06 PM

They don't do anything, because nothing uses them. You are free to define the run levels by modifying your init system as you see fit (i.e., a non-traditional configuration).

jimmy page · 01-08-2010, 12:15 PM

Quote:

Originally Posted by macemoneta

They don't do anything, because nothing uses them. You are free to define the run levels by modifying your init system as you see fit (i.e., a non-traditional configuration).

so they're not defined at all. thanks.
did they serve a purpose in old configuration "styles", or are they there just to give the user the option of using extra runlevels?

macemoneta · 01-08-2010, 12:21 PM

I'm not aware of any historical uses for those run levels as an installation default. You can use them for custom needs (start everything except networking, for example). There are only so many permutations that make sense for general use, and those are the runlevels that are defined.

jimmy page · 01-08-2010, 12:27 PM

Quote:

Originally Posted by macemoneta

I'm not aware of any historical uses for those run levels as an installation default. You can use them for custom needs (start everything except networking, for example). There are only so many permutations that make sense for general use, and those are the runlevels that are defined.

i see, thanks!

sundialsvcs · 01-08-2010, 08:46 PM

As you can see from perusing inittab, "run levels" are simply a way of grouping things. Ten digits equals ten groups.

It so happens, though, that no one has needed all ten group-numbers. So, they're just spares. "Feel free" to use them, though!