Delegates the authentication to the underlying Unix operating system user database. With this setting, users will be logged into Jenkins by entering their Unix username and password.

This mode will also allow you to use Unix groups for authorization. For example, you can say "everyone in the 'developers' group will have the administrator access".

Unix allows an user and a group to have the same name. If you need to disambiguate, you can use the '@' prefix to force the name to be interpreted as a group. For example, '@dev' would mean the 'dev' group and not the 'dev' user, while 'dev' would be interpreted as an user if you indeed have the user of that name.

This is done through a library called PAM, which defines its own configuration mechanism. It also works correctly with user database extensions like NIS.