how zabbix agent is running shell commands?

[reallove]

Hello,
I have a bit of concern the way system.run is executing commands on the agent, and also how the command defined by the UserParameter runs...here are the details...
I am using the zabbix-agent package from the Debian lenny repositories. Upon installation, it creates a system user 'zabbix' with the shell /bin/false.
Next, I want Zabbix to execute a command on the agent, /sbin/iptables. I've created in zabbix agent conf a custom user-defined monitored parameter (UserParameter), and then add the item on the server. I added a sudoers line, so zabbix can execute /sbin/iptables...and surprisingly it works.
My question is, how is zabbix executing the command, since it has no shell defined in /etc/passwd? If I su zabbix -c command, it doesn't work. How is then zabbix able to execute it?
Thanks, I hope my question makes sense.

[nelsonab]

It has nothing to do with your current shell, or the shell of the Zabbix user. I would have to look at the source but I'm willing to bet /bin/sh is called by the exec() library function call, which in turn is passed the subsequent command. This is likely hard coded and cannot be changed without recompiling the agent. This is pretty standard in the Unix world.

[reallove]

nelsonab, thanks, this sounds about right.