I often need to generate secure passwords for service accounts and what not. I could reach to one of the web-based “random” password generators, but I don’t trust Javascript enough–and you shouldn’t either. So, I’ve figured out a way to generate pseudorandom passwords, of any length, using nothing more than the standard tools provided by Linux:

$ </dev/urandom tr -dc [:graph:] | tr -d "Il10Oo\\\"'" | head -c 25; echo

Let’s break it down!

  • </dev/urandom
    • Provides a stream of pseudorandom characters.
  • tr -dc [:graph:]
    • Filters out all characters that are not graphical (printable).
  • tr -d "Il10Oo\\\"'"
    • Filters out all characters that are similar in shape.
    • Also filters out quotes and backslashes, as they might introduce problems when you copy/paste it into a command.
  • head -c 25
    • Output the first 25 characters.
  • ; echo
    • Syntactic sugar. It appends a newline character, outputting the password to its own line, thereby making it easier to copy/paste.

That’s it! To increase the password length (and thus security), adjust the “25.” To simplify execution, paste it into a bash function or bash alias.

The only caveat is that randomness–or pseudorandomness–is based on /dev/urandom, which requires that a system be able to generate enough entropy. On personal computers, this shouldn’t be a problem.