What's to say? Check my personal website for a touch more detail, if you want to. I've been a professional UNIX/network sysadmin since 1991, and currently sysadmin free software professionally through my own little company. A long time ago, I and a co-author wrote "Building Linux and OpenBSD Firewalls" (Wiley, 2000). That's it.
Q&A for professional system and network administrators
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems.
Q&A for professional and enthusiast programmers
Q&A for computer enthusiasts and power users
Q&A for Information security professionals
Q&A for Ubuntu users and developers
Q&A for road warriors and seasoned travelers
Q&A for active researchers, academics and students of physics
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Q&A for science fiction and fantasy enthusiasts
Q&A for Bitcoin crypto-currency enthusiasts
Q&A for software developers, mathematicians and others interested in cryptography