On Tue, 17 Jun 2003, Matthew Melvin wrote: > You seem to have it pretty much sus'ed excepted for the roll of inittab in > run level S. Yes init still looks in /etc/inittab when going to run level S > but if it doesn't find an entry, or the inittab can't be opened then it init > acts as if it had read.. > > ~~:S:wait:/bin/sh
ah, this is useful information, and is not mentioned *explicitly* in the man page for "init", which states simply that "Runlevel S or s bring the system to single user mode and do not require an /etc/inittab file. In single user mode, a root shell is opened on /dev/console." good to know. > ... from the file. So inittab is not required but nor is it ignored. On > some of my older systems I've overiden this with... > > ~:S:wait:/sbin/consolechooser > > ... where consolechooser is a script I wrote to deal with some serial > consoles that wouldn't behave themselves. > > With runlevel 1 your box still needs to have some basic funtionality, in run > level S, nothing really needs to work except /sbin/init and /bin/sh... it's > basically one step up from booting with init=/bin/sh ... using runlevel S > instead of the init= hack (assuming S works) really just means you don't > have to reboot the system to go back to a 'real' run level. just to clarify a few things i probably didn't cover clearly in my first post, it's fairly obvious what happens when you move between numbered run levels -- any of 1,2,3,5 -- with the "init" command. if you're, for example, in level 3, and type "init 2", init consults /etc/inittab, which causes all of the K and S scripts in /etc/rc2.d to be invoked, etc, etc. in addition, there is the "runlevel" command, which prints the previous and current runlevels, so that if you just changed from 3 to 2, the output will be "3 2". if you just booted, though, the runlevel output will be something like "N 3", since there *was* no previous runlevel. however, run level "s" (or "S") is different since it isn't defined in /etc/inittab. i was initially a bit confused when, from run level 3, i typed "init 1" and, after all the service shutdown, the runlevel command printed "1 S". that was a bit odd, i thought, since i never *asked* for single user mode, but it became clear when you look in /etc/rc1.d and notice that, after all the K scripts, the two S scripts are S00single (go to single user mode) and S17keytable. so, technically, going to run level 1 does take you eventually to single-user mode. but it's not clear if it's a good idea, from say run level 3, to type "init s" to go directly to single-user mode, since none of the /etc/rc1.d scripts will be run, and all your services will still be running (go ahead and try it, it doesn't seem to hurt anything). from what i read, going directly to single-user mode in this way is not recommended, and is supposed to be used only by other scripts or utilities. when you *boot*, however, it's fine to choose either run level 1 or, in the more extreme case if you've toasted your /etc/inittab, run level "s". ok, i think it all makes sense now. rday -- Robert P. J. Day Eno River Technologies Unix, Linux and Open Source training Waterloo, Ontario www.enoriver.com -- redhat-list mailing list unsubscribe mailto:[EMAIL PROTECTED] https://www.redhat.com/mailman/listinfo/redhat-list
