What's to say? Check my personal website for a touch more detail, if you want to. I 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
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Q&A for computer enthusiasts and power users
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Q&A for users of Linux, FreeBSD and other Un*x-like operating systems.
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Q&A for meta-discussion of the Stack Exchange family of Q&A websites
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Q&A for software developers, mathematicians and others interested in cryptography