I started working at a Linux based internet service provider in 1998 (before I could drive). Through the years I've worked in various positions as a Linux system administrator, a network administrator, a network engineer, a systems engineer, and a DBA (concentrating on MySQL and MongoDB).
I've been lucky enough to teach many people through my career. Some have gone on to become professional system administrators, some are software engineers or coders, and some are networking people. All have said that my teaching style is effective and approachable, so I've tried to capture that here.