pam_securetty.so  [
        debug
      ]
      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 the securetty file. pam_securetty checks at
      first, if /etc/securetty exists. If not and
      it was built with vendordir support, it will use
      %vendordir%/securetty. pam_securetty also
      checks that the securetty files are plain
      files 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
            securetty file.
          
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
            securetty file is world writable or
            not a normal file.
          
Memory buffer error.
The conversation method supplied by the application failed to obtain the username.
The conversation method supplied by the application returned PAM_CONV_AGAIN.
            An error occurred while the module was determining the
            user's name or tty, or the module could not open
            the securetty file.
          
            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.