We're using the latest Zabbix-agent (2.2.2) from the official repo on our Ubuntu 12.04 machines.
This is not working as it should, while troubleshooting it came to my attention that the pidfile is not being written which means the init script won't work!.

The pidfile is not being created, and if it exists it is not being updated. This results in:

===
root@server:~# date && service zabbix-agent restart
Thu Mar 6 11:55:55 CET 2014

• Stopping Zabbix agent zabbix_agentd
  No process in pidfile '/var/run/zabbix/zabbix_agentd.pid' found running; none killed.
  [ OK ]
• Starting Zabbix agent zabbix_agentd [ OK ]
  root@server:~# ps aux | grep zabbix-agent
  root 12329 0.0 0.0 9360 616 pts/0 S+ 11:55 0:00 grep --color=auto zabbix-agent
  root@natgate01:~# ps aux | grep zabbix_agent
  root 12343 0.0 0.0 9360 620 pts/0 S+ 11:56 0:00 grep --color=auto zabbix_agent
  zabbix 16058 0.0 0.1 88172 1200 ? S Feb18 0:00 /usr/sbin/zabbix_agentd
  zabbix 16059 0.0 0.1 88172 1200 ? S Feb18 3:28 /usr/sbin/zabbix_agentd: collector [idle 1 sec]
  zabbix 16060 0.0 0.1 90252 1564 ? S Feb18 0:02 /usr/sbin/zabbix_agentd: listener #1 [waiting for connection]
  zabbix 16061 0.0 0.1 90252 1564 ? S Feb18 0:02 /usr/sbin/zabbix_agentd: listener #2 [waiting for connection]
  zabbix 16062 0.0 0.1 90252 1564 ? S Feb18 0:02 /usr/sbin/zabbix_agentd: listener #3 [waiting for connection]
  ===

Zabbix is not being stopped or restarted, even though it claims it was. Adding the pidfile of the master process to the pidfile has no effect on stops and the file is never updated.