General ungleich knowledge base¶

Introduction¶

This knowledge base documents topics/problems that we found helpful to not repeat again.

Postfix name resolving issues¶

Some of our virtualised servers had the problem that postfix was unable to resolv domains, even though the network configuration (DNS, routing) is correct. The reason for this was an incorrect startup order: postfix was started before the network setup (in our case the opennebula contextualisation) finished. Thus postfix copied the empty /etc/resolv.conf to /var/spool/postfix/etc/resolv.conf and would not update this anymore.

Typical log lines that we have seen are:

Jul 29 21:58:41 mx postfix/error[6542]: 1A8BE211BB: to=<XXXXXXX@gmail.com>, orig_to=<XXXXXXXX@ungleich.ch>, relay=none, delay=1080070, delays=1080069/0.27/0/0.02, dsn=4.4.3, status=deferred (delivery temporarily suspended: Host or domain name not found. Name service error for name=gmail.com type=MX: Host not found, try again)

The correct solution is obviously to ensure that postfix is started only after the network is fully up.