Generate a random password in the terminal

openssl rand -base64 24

That gives 32 characters of letters, digits, +, / and maybe a trailing =. For only letters and digits:

tr -dc 'A-Za-z0-9' < /dev/urandom | head -c 32; echo

And if you want something you can actually read out loud over the phone, pwgen is a small package:

pwgen -s 20 1