Results 1 to 5 of 5

Thread: 'authentication failed' and 'unknown module' errors preventing logon

Threaded View

  1. #1
    Join Date
    Apr 2007
    Location
    Pompano Beach, FL, USA
    Beans
    69
    Distro
    Ubuntu 13.10 Saucy Salamander

    Lightbulb 'authentication failed' and 'unknown module' errors preventing logon

    Effected Systems:
    I experienced this issue on Hardy but I found evidence of it occurring on earlier versions and on Debian.

    Symptoms:
    • You can't login using your normal credentials. Logging on in X (the graphical environment) raises an "authentication failed" error and the shell complains about an "unknown module".
    • You can access the system in recovery mode and you can confirm that the users and passwords are set correctly.
    • Attempting the su command from the shell raises "Unknown module: su" but you may be able to switch users (in single user mode)
    • You may also see "Segmentation fault" errors.
    • The system logs provide no help, there is no entry related to this failure.


    Cause:
    PAM (Pluggable Authentication Modules) is failing to authenticate you because it can't load its essential modules.

    Resolution:
    **WARNING** Following these directions should be safe but you will run a potentially dangerous command. Take the proper precautions like backing up important data or the entire system. **

    If you haven't messed with PAM the easiest thing to do is to take it out and replace it with a working copy from the official repositories.

    Step 1: Start ubuntu using the recovery option (singe user mode)

    Step 2: Purge the pam runtime and modules packages and some related files (don't try using apt for this):
    Code:
    dpkg --force-all --purge libpam-runtime
    dpkg --force-all --purge libpam-modules
    rm -rf /etc/pam.d
    rm -rf /lib/security
    Step 3: Reinstall those packages from the repositories:
    Code:
    apt-get install libpam-runtime libpam-modules
    Step 4: Reboot. You should be able to login normally now:
    Code:
    reboot now
    Notes:
    My main source for fixing my issue and deriving these instructions:
    http://unixadmintalk.com/f11/cannot-login-su-73323/

    The user in the following post had a similar issue but fixed it a different way, which did not work for me:
    http://www.linuxquestions.org/questi...unknown-25194/
    Last edited by MikeEvans; May 21st, 2008 at 07:46 PM.

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •