It's tough to know, but my bet is that they will test a couple of basics, at least:
1. Run levels
2. Start up scripts
3. User/group adding, ownership changes
4. Process/daemon lifecycle - starting, stopping, monitoring, killing, etc
5. Performing actions with the network - ifconfig, ifup, iptables maybe
I would think they would use these types of topics because they are fairly similar across most distros and even most Unices. If you're know the commands and the most commonly used switches for the above mentioned topics, you're probably in ok shape.
