The default Linux password policy, which is based on a US standard keyboard and the default password limits for PAM Module Configuration, calls for a minimum of 14 characters, with at least 1 uppercase character, 1 lowercase character, 1 alphanumeric character, and 1 special character. The following characters are not permitted: pound (#), dollar ($), apostrophe (’), double quotes ("), backslash (\), space, and any ASCII control character.