"Organizations count on systems administrators to ensure that their computers and software are fully functional. In an interview, expect technical questions that will test your ability to troubleshoot relevant computer issues. Because systems administrators often play the role of customer supporter, be prepared to answer a situational question about dealing with a difficult customer. In addition, make sure to highlight your interpersonal and communication strengths as well as your ability to clearly explain technical concepts to a non-technical audience."
Tell us a mistake you made at work
Forgot to include new mounted partition in /etc/vfstab and when systm rebooted, it was lost.
The question isn't about the mistake, it is about how you recovered from it and learned from the mistake. Be sure to include your lessons learned.