I have been using computers for over 20 years, starting with Sinclairs, Apple II, Commodore 64's, TRS-80, and CP/M based stuff. I have managed SunOS 4 workstations, firewalls of all sorts, Linux, FreeBSD, AIX and Solaris servers, done a fair share of network switching&routing management (from vlans and port mirroring all the way up to BGP routing), and even been a FreeBSD committer for a few years.