A really useful tool for quickly generating random passwords in Linux is pwgen.

Install with sudo apt-get install pwgen (on Debian based systems) and then use pwgen to fill your screen with randomly generated passwords.

It’s possible to add params in order to customize your generated passwords. These are listed below.

-c Include at least one capital letter in the password
-A Don’t include capital letters in the password
-n Include at least one number in the password
-0 Don’t include numbers in the password
-y Include at least one special symbol in the password
-s Generate completely random passwords
-B Don’t include ambiguous characters in the password
-h Print a help message
-H Use sha1 hash of given file as a (not so) random generator
-C Print the generated passwords in columns
-1 Don’t print the generated passwords in columns
-v Do not use any vowels so as to avoid accidental nasty words