On Sat, 25 May 2002, Bret Hughes wrote:
> Is the issue whether s is entered at boot or via telinit? Not sure but
> like Mr Wagner, I have always assumed 1 and s were the same but clearly
> they are not.
>
> Keep us informed of any progress you make on figuring this out.
i can tell you what piqued my curiosity. i was explaining the "runlevel"
command, which shows you two pieces of info -- the previous run level
and the current level. if you've just booted to run level 3, say,
that command will show you:
# runlevel
N 3
as in, this machine came from a New boot (really, no previous run level)
and is now in 3.
if you change run levels using "init", say "init 2", then runlevel
will tell you:
# runlevel
3 2
so far, so good.
if, however, you take it down to runlevel 1 with "init 1", you get:
# runlevel
1 S ?????
in other words, switching to run level 1 involves init consulting
/etc/inittab, running everything in /etc/rc1.d (mostly K scripts),
but the last two entries in /etc/rc1.d are S00single and S17keytable,
which takes you from run level 1 to run level S.
so far, i've established that {S,s} is *not* equivalent to 1,
since run level 1 does consult /etc/inittab, while {S,s} does not.
and, as far as i can tell, you're supposed to go to single-user mode
by going to run level 1. as a test, try "init s" and see what
happens. very different from "init 1" -- with "init s", none of
/etc/rc1.d is consulted, so services are *not* killed.
i also quote from "linux administration handbook," by nemeth et al.
"Single-user mode was traditionally init level 1. It brought down all
multiuser and remote login processes and made sure the system was
running a minimal complement of software. Since single-user mode
provides root access to the system, however, administrators wanted
the system to prompt for the root password whenever it was booted
into single-user mode. The S run level was created to address this
need: it spawns a process that prompts for the root password. On
Linux, the S level serves only this purpose and is not a destination
in itself."
other than the fact that my red hat box does *not* prompt for the
root password, this emphasizes that 1 != s yet again. anyway, i
think i'll rename /etc/inittab and have some fun experimenting with
1 versus {s,S}. but, as i said, i think it's pretty clear that
1 != s.
rday
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