Job interview questions for system administrators

During the last few weeks I interviewed quite a few candidates for the position as a system administrator in our company (job ad here). But what questions do you ask a prospective administrator to check whether he or she has the needed skills for the job? We needed someone who could administer a Windows domain and some Linux servers, all virtualized by VMWare. For me, it was almost instantly clear that theoretical questions alone would not suffice to form an opinion of the candidate’s skills.

The developers I interviewed for another position needed to “pair program” (although in fact they were the only ones to write a line of code) some small applications with me. There are tons of example programs out there for this task. For example, I chose FizzBuzz, a linked list, and a prime factors generator. By watching the contestants program “live” you can get a good grasp of their programming and analytical skills very quickly.

So, a colleague and I tried to come up with a small test for our new administrator and ended up with a scenario in a virtualized Windows/Debian environment. We provided a W2K8 domain controller and two Windows 7 clients, of which one had direct network access to the DC and the other one was in another virtual network. The Debian server was in the same network as the DC but had the wrong IP configuration. In this environment the candidate had to work through a bunch of tasks right at the keyboard/screen so we could watch if and how he managed the tasks, whether he used keyboard shortcuts or the online help, knew the needed tools (e.g. ping, nslookup), etc. By doing so, we were able to objectively rate the contestants’ results opposed to each other and quickly found our new colleague 🙂

Here are some of the tasks the candidates needed to perform:

• connect to the DC via RDP
• add some OUs, users and groups to the Active Directory
• configure the ACLs of a network share
• assign a network share to a user as a network drive
• add a machine to the domain
• find network configuration errors and reconfigure the machine
• add a new harddisk to the DC (in VMWare and in Windows)
• add and configure a GPO
• configure a user to use a roaming profile
• configure and activate a NIC under Debian
• mount a network share
• share a directory with samba
• find common mistakes in a given Word document (e.g. manual page numbers and table of contents)

The fastest contestant took the test in about an hour without any bigger problem. The slowest contestant didn’t even know how to connect to the DC. As with developers, it all comes down to the tiny problems…