[Dovecot] Signal 11 - can't get core dump?

[Timo Sirainen]

On 25.8.2010, at 0.09, Marty Anstey wrote:

> However, over the past month or so we've begun to experience issues
> where IMAP clients will appear to "hang" for a period of time, we then
> see a sig 11, and afterwards mailflow returns to normal. This usually
> happens a few times a day.
> 
> Naturally, our first instinct was to try and get a core dump, but after
> following the instructions at http://www.dovecot.org/bugreport.html we
> now recieve this warning:
> 
> 2010-08-24T13:33:56-07:00 mail dovecot: child 9728 (login) killed with
> signal 11 (core not dumped - add -D to login_executable) (ip=208.98.210.13)

This is a pre-login crash. Those can be difficult.

> Adding -D to the login_executable lines didn't seem to have any effect,
> we are still receiving the same message. Did we perhaps misinterpret the
> hint?

That should work with Linux. But maybe it doesn't work with all kernels. A few things you could anyway try:

 - check that /var/run/dovecot/login directory is writable by the login process user (dovecot I guess)
 - try login_chroot=no
 - echo 2 > /proc/sys/fs/suid_dumpable

> # 1.1.20: /etc/dovecot.conf

Unless the crash is something simple (which I doubt it is), I don't really want to spend time trying to debug and fix it for v1.1 anymore. There's a good chance it's already fixed in v1.2 (and a very good chance it's fixed in v2.0).

You could also try setting login_process_per_connection=no. That makes login processes behave quite differently and could also happen to fix this.