pam_securetty man page
pam_securetty — Limit root login to special devices
pam_securetty is a PAM module that allows root logins only if the user is logging in on a "secure" tty, as defined by the listing in /etc/securetty. pam_securetty also checks to make sure that /etc/securetty is a plain file and not world writable. It will also allow root logins on the tty specified with console= switch on the kernel command line and on ttys from the /sys/class/tty/console/active.
This module has no effect on non-root users and requires that the application fills in the PAM_TTY item correctly.
For canonical usage, should be listed as a required authentication method before any sufficient authentication methods.
Print debug information.
Do not automatically allow root logins on the kernel console device, as specified on the kernel command line or by the sys file, if it is not also specified in the /etc/securetty file.
Module Types Provided
Only the auth module type is provided.
The user is allowed to continue authentication. Either the user is not root, or the root user is trying to log in on an acceptable device.
Authentication is rejected. Either root is attempting to log in via an unacceptable device, or the /etc/securetty file is world writable or not a normal file.
An application error occurred. pam_securetty was not able to get information it required from the application that called it.
An error occurred while the module was determining the user's name or tty, or the module could not open /etc/securetty.
The module could not find the user name in the /etc/passwd file to verify whether the user had a UID of 0. Therefore, the results of running this module are ignored.
auth required pam_securetty.so auth required pam_unix.so
securetty(5), pam.conf(5), pam.d(5), pam(8)
pam_securetty was written by Elliot Lee <email@example.com>.