topic Re: Runlevel Definitions in Operating System - HP-UX

Runlevel Definitions

Colleen_4 — Tue, 08 Apr 2003 16:29:41 GMT

Hi all,

I'm trying to figure out what the various runlevels on HP-UX 11.X mean. Here's what I have so far:

0 - halt
1 - Single user
2 - Multi user w/ network
3 - Multi user w/ network and GUI
4 - reboot

Am I right?

Thanks in advance for your help...

Re: Runlevel Definitions

Pete Randall — Tue, 08 Apr 2003 16:31:53 GMT

I'm not sure what you mean by "4 - reboot", but other than that, you're correct. As used nowdays, only the first 3 runlevels have meaning. Runlevels above 3 are user-defined.

Pete

Re: Runlevel Definitions

James R. Ferguson — Tue, 08 Apr 2003 16:41:25 GMT

Hi:

See the man pages for 'init(1M)' for the values.

Regards!

...JRF...

Re: Runlevel Definitions

John Dvorchak — Tue, 08 Apr 2003 16:50:44 GMT

Interesting since man 1m init says that run level 4 is where the GUI starts up but on all of mine there isn't anyting in /sbin/rc4.d the GUI and my/company'e stuff is in rc3.d. I kind of remember int he old days, when I still had short term memory, that run level 4 was where the GUI started.

In any event the list you have is correct except for 4 being reboot. Maybe someone at your location got creative and installed a reboot script there.

Good luck

Re: Runlevel Definitions

Robert Gamble — Tue, 08 Apr 2003 17:06:12 GMT

Yep, anything above run level 3 is user defined since 10.20.

At some of my customer locations, in rc4.d we put in scripts enabling the predictive modem to allow dial-in for support issues. A very nice tool to quickly enable/disable non-critical services.

Caution: do not run down a level from level 3. It is unsupported and may cause unpredictable results. Use the shutdown command to reboot and then go to single-user mode if necessary.

Good Luck!

Re: Runlevel Definitions

Colleen_4 — Tue, 08 Apr 2003 18:01:27 GMT

So the consensus is that the man page is outdated?

Just to clarify, the only runlevels with networking are 2 and 3?

Re: Runlevel Definitions

Pete Randall — Tue, 08 Apr 2003 18:06:33 GMT

Colleen,

Yes, that's correct on both counts. The man page is outdated and the only runlevels with networking are 2 and 3.

Pete

Re: Runlevel Definitions

T. M. Louah — Tue, 08 Apr 2003 18:08:23 GMT

networking start at rl 2 , & any thing on top of it will be at run level 3, for example NFS has 3 basic componenets nfs.core starts in rl 2 & nfs.server/client starts at rl 3, so in order to get nfs to run we need networking to start first!
T??

Re: Runlevel Definitions

Patrick Wallek — Tue, 08 Apr 2003 18:10:41 GMT

Networking is started at run-level 2 and is available at all higher run-levels.

Run level 1 (aka single-user mode) has no mounted filesystems, no applications started, very few OS services started and no networking. Run level 1 is accessable from the console (serial console, LAN console, web console) only.

Re: Runlevel Definitions

John Dvorchak — Tue, 08 Apr 2003 18:11:41 GMT

I agree the man pages are a bit dated. Remember that init runs up and down the list. From boot up it goes level 1 then 2 then 3 and if anything in 4 then it will got to 4 and above. On shutdown it goes from it's current run lever down back to 2 then to 1 and finally to 0. One tip that you should be aware of is that it is NOT suggested to go into Single user mode from a run level above. The only suggested way to enter Single user mode is from boot up, interact with the ISL and issue the HPUX -is command. I beleive the reason is that going from runlevel above 1 to level one doesn't really kill all of the sytem processes and results will be unpredictable.

Good luck

Re: Runlevel Definitions

Michael Steele_2 — Tue, 08 Apr 2003 23:30:29 GMT

You're missing S - single user mode, see the init command.

s/S - single user
0 - halt, etc.

Those man pages are obsolete since 10.20 and 10.30.

Server network services startup at run level 2.

Client network services startup at run level 3. (* NFS for example. *)

These commands were significant when executing commands like: init 1, or init s/S in order to come down from multi user mode into a lesser run level, init s for example.

Consequently, attempting an 'init s' will no longer stop network processes.

I believe Solaris and Linux still support these init commands with run levels.

Re: Runlevel Definitions

RolandH — Wed, 09 Apr 2003 11:55:49 GMT

Hey John D. you are NOT right with "and if anything in 4 then it will got to 4 and above"

Take a look in /etc/inittab first line.
What is there per default ?!
init:3:initdefault:

This means if the system has reached runlevel 3 it will stop to go further runlevels besides you have changed the runlevel explicit with init command or antoher default runlevel

Roland

Re: Runlevel Definitions

Stuart Abramson_2 — Wed, 09 Apr 2003 19:45:22 GMT

We put all of our user applications, like oracle, etc, in run level 4. We consider this a best practice. It seperates the user applications from the system applications, a few of which still start in run level 3 (nfs!, dtlogin).

So, we:
1. We change the first line of inittab from a "3" to a "4", so the system actually comes up to run-level 4 at boot.
2. We put our start scripts in /sbin/rc4.d/:
cd /sbin/rc4.d/
ln -s /sbin/init.d/oracle S100oracle

I would rewrite your list as (on our systems):

0 - halt
1 - Single user
2 - Multi user w/ network
3 - Multi user w/ network and GUI
4 - user applications

and you forgot run level "S" and logical volume maintenance mode.