More than 20 years experience on Linux as both a user and as an administrator. Fully conversant with iptables, ipchains, the LAMP stack, dovecot, postfix, sendmail, and the full complement of the command line swiss army knife.
More than 10 years experience working with Asterisk and FreePBX in a number of different environments. Currently managing phones systems for 25 medical clinics, 10 care homes, two head end installations, one ip centrex phone system, and two office phone systems. Also manage approximately ten remote connections.
I am extremely comfortable using bash shell scripting and moderately comfortable with perl, and can use python if the situation is suitable. If all else fails, I can always code something up quick in C or C++ to fix a particularly sticky problem.
I have four years experience with packet tracing which can come in very handy for network problems.
I have two years experience heavily using iptraf, iotop, iostat, iperf, netstat, ip, ifconfig and related tools to profile performance problems in a production environment (a production 300MP camera assembly running across 10Mb fibre connections, fully saturated), dumping data to SAS-attached SATA drives.