I'm working with and for UNIX for nearly 20 years now ...
there are some things I know about that stuff but there is also still a lot to learn;
here is a short list of UNIX'es I'm using or I used: UNIX SVR4.2,
SuSE Linux (that's the system I'm using on my notebook now),
Onsite UNIX and UnixWare 2.1.2 (these systems I also run at
home), AIX 4.x, Sun Solaris 2.6, SCO OpenServer,
and (a little bit outdated) UNIX Version 7 for the PDP-11.
TCP/IP and network topics
Years ago I started with an old 2400 bps modem (it's still in use
to reset a PC based router by shorting the motherboard's
reset line from an ATDP1
command via a crontab script :-)) -- today I'm using ISDN routers
(Ciscos and Telebit NetBlazers) and have some experience
with the protocols they're using (PPP, PAP and CHAP) and how
to build secure networks with firewall software.
Facsimilie software and modems
I was a maintainer of a free facsimilie software package
written in C++ for UNIX systems
(Sam Leffler's HylaFAX) and
we're also selling HylaFAX to our customers; now the software is
and I'm no longer involved in that project.
ISDN and GSM / GPRS
I was forced to know the details of ISDN to write a driver
for my FreeBSD notebook's ISDN PCMCIA card; now GPRS with
GSM mobiles is (at
least here in Germany) ready to use, and normally I run my Linux notebook
and connect it with my company network over GPRS; it's very
nice to access your mailbox from where-ever you are.