Passwords should be long, random, and difficult to guess. Special characters improve password complexity, but they can also cause unexpected behavior when passwords are entered through Linux commands, scripts, or configuration files.

Linux itself generally accepts special characters in passwords. The issue is often the shell interpreting those characters before the password reaches the application.

Characters such as the following may have special meanings in shells such as Bash, which is used by SUSE Linux (@ and ~ are always prohibited in the RSA database):

@ ~ $ ! * ? ; & | < > ( ) \

Depending on the shell and its configuration, characters such as ! can have special meaning. Bash, which is used by SUSE; for example, using $ can trigger variable expansion, * and ? can be interpreted as wildcards, and ! can trigger history expansion.

As a recommended practice,

• Use an interactive password prompt whenever possible. Entering the password at the prompt prevents the shell from interpreting it as part of the command.
• Avoid placing passwords directly on the command line.
• If the special characters listed above are required, use them at the end of the password. For example, P4ssw0rd! rather than P4!ssw0rd.
• If a password must be supplied to a shell command, use appropriate quoting/escaping for the shell and application. Remember that different applications may have their own parsing requirements.