Date: Thu, 21 Sep 1995 07:12:23 -0400 (EDT) From: Bill/Carolyn Pechter <pechter@shell.monmouth.com> To: kelly@fsl.noaa.gov (Sean Kelly), ports@freebsd.org Subject: Re: ports startup scripts Message-ID: <199509211112.HAA10159@shell.monmouth.com> In-Reply-To: <9509210011.AA06450@emu.fsl.noaa.gov> from "Sean Kelly" at Sep 20, 95 06:11:13 pm
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> And it's not clear what run levels are. On the HP/UX system I'm using
> at the moment, there are run levels 0 through 6 and S. S is the only
> one that really makes sense (S == single user), but why is 2 multiuser
> mode? What do you get with levels 0 and 1? What don't you get? And
> sites can customize the higher run levels to mean what they want.
Boy... I guess coming from the other coast and growing up with AT&T
Unix makes me spoiled.
The reasons for the additional multi user run states are daemon process
control. Ever want to run multiuser w/o networking. Ever want to run
multiuser with just console getty for admin testing...
This lets you control just how much system is available to the users.
It's really more useful on large machines than workstation boxes, since
it's more likely that you would be controlling large numbers of users
on a Pyramid MIS multiprocessor server than on a Sparc2.
Here's a compilation of what I've seen used in real life.
Levels 0,1,2,3 and 6 are pretty standard in the AT&T Unix world.
The one thing I noticed was that HP's implementation stinks. On HP-UX9.x
on their workstations they never check the current run level and try to
rerun /etc/rc stuff at run level changes.
Correctly configured machines do who -r and base their startup scripts
on previous levels... i.e. going from 0 to 2 will start up daemons.
Going from 3 to 1 and then to 2 will not restart all the level 2 daemons
and rerun the full /etc/rc*.
HP-UX is very unusual in their startup scripts.
S,s -- Single User
0 -- Halt, (powerdown if this can be done by software -- it is in 3B2's)
1 -- System Admin mode. Getty on console, daemons running
2 -- Multiuser mode
3 -- Often used for multiuser with networking running
Solaris starts nfs here. HP starts Vue's XDM-like vuelogin
here and at run state 4
4 -- User defined
5 -- User defined
6 -- Reboot
a,b,c -- Pseudo-run level -- used to run a specific program --
does not really change run state of system -- sometimes used
to fire off database daemons...etc.
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