DOKK / manpages / debian 12 / libpam-modules / pam_localuser.8.en
PAM_LOCALUSER(8) Linux-PAM Manual PAM_LOCALUSER(8)

pam_localuser - require users to be listed in /etc/passwd

pam_localuser.so [debug] [file=/path/passwd]

pam_localuser is a PAM module to help implementing site-wide login policies, where they typically include a subset of the network's users and a few accounts that are local to a particular workstation. Using pam_localuser and pam_wheel or pam_listfile is an effective way to restrict access to either local users and/or a subset of the network's users.

This could also be implemented using pam_listfile.so and a very short awk script invoked by cron, but it's common enough to have been separated out.

debug

Print debug information.

file=/path/passwd

Use a file other than /etc/passwd.

All module types (account, auth, password and session) are provided.

PAM_SUCCESS

The new localuser was set successfully.

PAM_BUF_ERR

Memory buffer error.

PAM_CONV_ERR

The conversation method supplied by the application failed to obtain the username.

PAM_INCOMPLETE

The conversation method supplied by the application returned PAM_CONV_AGAIN.

PAM_SERVICE_ERR

The user name is not valid or the passwd file is unavailable.

PAM_PERM_DENIED

The user is not listed in the passwd file.

Add the following lines to /etc/pam.d/su to allow only local users or group wheel to use su.

account sufficient pam_localuser.so
account required pam_wheel.so

/etc/passwd

Local user account information.

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

pam_localuser was written by Nalin Dahyabhai <nalin@redhat.com>.

09/03/2021 Linux-PAM Manual