They call and ask basic customer service questions then ask to schedule an interview.

After an initial phone screening from HR I took another interview/test with an administrator. I SSH'd into a box they had setup and performed some steps that he told me over the phone. The technical interview was fairly easy, especially since I could take my time and was allowed to look up any details/man pages when needed.

The entire process took 1 week from initial interview to job offer. The first interview was question-based. They were looking for your experience and what your thought process was. The second part was an interactive interview, where you logged into one of their test environments and performed various commands and demonstrated various skills like searching, creating files with one command, networking terms, ports, etc. A lot of focus on CentOS, cPanel, and Linux.