I have been using Unix (and later Linux) for 30 years. Linux since mid 90s, more distros than I can count. I've also worked with SCO, Novell Unixware, SysV, BSD, Solaris, SunOS, IRIX, and likely more that I can't remember. I've dealt with everything from old RS232 and CSU/DSU units to modern network gear and machine sizes from tiny embedded devices to Sun E10000s.