On Thu, 2011-11-24 at 19:23 +0100, Miguel Tormo wrote:
The fd limit is the maximum number of concurrently open file descriptors per process. It can be configured on a per-user basis. You can check the actual value running 'ulimit -n'. It can be increased up to the value set in /proc/sys/fs/file-max. You can set it editing /etc/security/limits.conf.
I'm not sure if changing /etc/security/limits.conf helps. It's probably only used by PAM when user logs in, so if Dovecot is started in system bootup it's unlikely to have been even read yet. Also I think some OSes override the limits in /etc/init.d/ scripts. Of course, I could be completely wrong in all of the above, I haven't really tested any of it :)
What the above comment means is that under max load the auth service could need up to 4096 file descriptors open, that's more than the default in most linux systems (1024).
I wonder if there's a good reason for why auth default should be that high. Probably in earlier times imap/pop3 processes just weren't disconnecting early enough from auth. So I guess I'll just drop it back to default and this warning would go away in most systems. I had started to get a little bit annoyed at that warning myself also.