pam_rootok - Gain only root access

       pam_rootok was written by Andrew G. Morgan, <morgan@kernel.org>.

Linux-PAM                                          07/03/2025                                      PAM_ROOTOK(8)

       pam_rootok is a PAM module that authenticates the user if their UID is 0. Applications that are created
       setuid-root generally retain the UID of the user but run with the authority of an enhanced effective-UID.
       It is the real UID that is checked.

       In the case of the su(1) application the historical usage is to permit the superuser to adopt the
       identity of a lesser user without the use of a password. To obtain this behavior with PAM the following
       pair of lines are needed for the corresponding entry in the /etc/pam.d/su configuration file:

           # su authentication. Root is granted access by default.
           auth  sufficient   pam_rootok.so
           auth  required     pam_unix.so

       The auth, account and password module types are provided.

       pam_rootok - Gain only root access

       debug
           Print debug information.

       PAM_SUCCESS
           The UID is 0.

       PAM_AUTH_ERR
           The UID is not0.

su(1), pam.conf(5), pam.d(5), pam(7)

pam_rootok.so [debug]