Too many topics, too little time

dmiessler.com | study | lsof:
lsof is the Linux/Unix über-tool. I use it most for getting network connection related information from a system, but that’s just the beginning for this amazing and little-known application. The tool is aptly called lsof because it “lists open files”. And remember, in Unix just about everything (including a network socket) is a file.

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handy primer on lsof