If I run zabbix_agentd in an LXC client, then it fails to start with

1. zabbix_agentd -c /etc/zabbix/zabbix_agentd.conf
   zabbix_agentd [943]: ERROR: invalid host name: []

The log file is not written at all, even with Debug=4.

If I don't define a Hostname in zabbix_agentd.conf, then there is no such problem.

This might be related: On the client command line I get

1. hostname
   tricia
2. cat /etc/hostname
   tricia.mydomain.de
3. hostname --fqdn
   hostname: Name or service not known

It seems that the domain name part is cut off in the LXC client. On a real system "hostname" would have reported "tricia.mydomain.de", and "hostname --fqdn" wouldn't fail.