Linux Command One-Liners
Nice list, here are suggestions for improving a few of the commands:  Generate Random Passwords
  >_ < /dev/urandom  tr -dc _A-Z-a-z-0-9 | head -c6

This produces a 6-character password which only has 35 bits of entropy. It also doesn't print a newline, causing the password to be on the same line as the next prompt. Better to use something like:  >_ < /dev/urandom  tr -dc _A-Z-a-z-0-9 | head -c12 && echo

Or the "pwgen" utility which can do this for you.  Find the process that is using a certain port e.g. port 3000
  >_  lsof -P | grep ':30000'

This command will be extremely slow on large systems with a lot of open files. It is essentially listing every open file (the -P flag just inhibits port mappings from e.g. "port 22" to "SSH") and then grepping the output. Much better to run:  >_  lsof -i :30000

Which is not only shorter, but much faster as it directly gets info about that port.  Add your public SSH key to a server in one command
  >_  cat .ssh/id_rsa.pub | ssh hostname 'cat >> .ssh/authorized_keys'

This is what the "ssh-copy-id" utility, which is part of the openssh-client package, does already.  Harder, Faster, Stronger SSH clients
  >_  ssh -4 -C -c blowfish-cbc

All three of those points are debatable with that command. Just use the defaults.