My Ubuntu 14.04 LTS Desktop was working fine until I decided to play around with Google Two Factor Authentication for Linux.

I followed instructions and setup the google-authenticator.

When I restarted, the machine had a loop on login screen - after entering password and OTP from Google App, login screen was being displayed again.

I removed google-authenticator, uninstalled lightdm, installed Gnome, did "chown $username:$username ~${username-home}", but nothing has worked.

Any ideas?

  • Just to be sure, this is happening for all users. ssh login works, so does console login on same desktop. – user5837230 Feb 4 '16 at 3:56

You removed the module... but you didn't remove the requirement from your PAM configuration!

If you edited the file /etc/pam.d/lightdm you now need to (through a TTY or root-prompt from recovery mode) edit it again and remove the line:

auth require pam_google_authenticator.so nullok

If you edited any other file in the /etc/pam.d/ directory, you need to remove that line from whichever files you modified.

  • 1
    If you had followed my Q/A on this site and did the last section where you applied it to the /etc/pam.d/common-auth file, you probably forgot to remove the modifications to other files. This caused login to require the OTP twice which causes the loop. I'll bold and make that note a sub-heading in my answer. – user323419 Feb 3 '16 at 15:29
  • Hi, lightdm is completely removed from system. File /etc/pam.d/lightdm is not present. – user5837230 Feb 3 '16 at 15:32
  • What about /etc/pam.d/common-auth? Just do a ls /etc/pam.d/ and see which files are in there. Cycle through all of them and remove that line if present in any of them. – user323419 Feb 3 '16 at 15:34
  • cat /etc/pam.d/* | grep 'google' displays nothing. – user5837230 Feb 3 '16 at 16:05
  • Is it still asking for a OTP when you try to log-in? – user323419 Feb 3 '16 at 16:08

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