No space left on device prevents login

Question

It seems that when you run out of disk space all remote logins are prevented [I'm using Red Hat 4.4]. Apparently this is because all non-superuser logins have to write to /var/log/auth.log

This is a common occurence when /var/tmp/cores gets filled due to (user) programs crashing, or a process generating tons of log (under /var/tmp).

What configuration changes can be made to prevent this occurring?

Can + do you:

put /var/tmp on a different filesystem?
put /var/log on different filesystem?
enforce a strict separate of filesystems accessible user + system processes?

And what do you do, when the other filesystem is full, too? You'll not be able to login either. You need to react when the filesystem reaches the limit, either manually or automatic. — ott--, Dec 27 '12 at 11:50
@SohamChakraborty Nobody's paying _me_ to support RHEL4 anymore. — Michael Hampton, Dec 27 '12 at 16:20

score 3 · Accepted Answer · answered Dec 27 '12 at 11:59

There are several things that you need to do to prevent problems and possibly system crash in the future:

Create separate partitions for /var, /var/log, /tmp and possibly others to help your system survive (hopefully) in case of one partition got filled accidentally.
Use reasonable logrotate configuration to allow a good amount of logs and not consuming a lot of space. You can also compress the logs to reduce log size.
Run some monitoring tools to inform you early enough when you are about to exceed some configured threshold such 50% or 75% of your partition(s).
Fix any buggy software or lower the debug level when applicable and not needed. BTW, lowering debug level will improve performance.

No space left on device prevents login

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