I just ran 'chmod -x /bin/chmod'. What did I do? How do I recover?
Describe TCP's handshake process.
How does traceroute work?
When might you need to use CTRL-Z or CTRL-D?
What does the sticky bit do?
What kernel options might you need to tune?
How do you tell what distribution you're running?
How do you tell what hardware you're running on?
What is the difference between a SAN, a NAS and local disk?
I have 30 servers and I'm not sure if each has the same apache config.
How do I find out how many copies there are and what the differences are?
What's a chroot jail?
How do you tell if you've been hacked?
Name all the two letter unix commands you can think of and what they do?
How you could look up all the two letter unix commands on your system.
I also ask folks pre-onsite to do some simple homework. Especially if they profess some experience writing scripts. I ask them to parse two different data files (one csv, one |sv) and effectively do a join of the data. I put in a few gotchas (poorly formatted data), missing fields needed for joins, strangely out of sequence data, etc.. I ask them to send me the source code and output. (Machine Problem style) I usually give a 3-4 hour time window to tackle it. This task has helped filter out lots of candidates who list 'scripting' as a skill, but can't pull off basics when pressured.