Unix Toolbox
The Blog of Tom Webster
A couple days ago I came across this link which is really helpful. A one-page reference for TONS of *nix commands. Everything from SSH tricks, to database commands, to encryption is here. Pretty handy!
Just a caveat: In the ssh section, don't use DSA keys, use ED25519 or RSA (4096 bit) keys. I imagine some of this information is older, keep an eye out.