HR contacted me from LinkedIn.

There were three phone interviews for screening, a code test, and a system administration test.

In the first interview, the recruiter went through some questions, such as port numbers, routing, Linux commands, and some basic language-related questions.

The second interview was a coding test. An engineer had me write two scripts for CSV data processing and system monitoring.

The third interview was for system administration. The questions were pretty open. The interviewer had me dig into the internals of the operating system, such as performance tuning, memory model, paging, swap, process forking, system calls, interrupts, and so on.

I passed the three interviews and flew to the Facebook campus for a whole-day onsite interview (with an NDA signed).

During the interview process, I felt the people there were super nice and gave me chances to answer questions correctly.

My suggestions:

• Use your strongest language (a scripting language will help a lot).
• Be familiar with operating system internals and system analysis tools.
• Be familiar with networks and infrastructures (TCP/IP, DNS, HTTP, and so on).
• Think about scalability.

How can you find whether a process is I/O bound or CPU bound?