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I just updated 14.04 to latest patches using the GUI: software update. After that, a restart was required, and now cannot log into any of my accounts. I am sure the passwrds are all correct, it just bounces me back to the same login screen (as opposed to when I really type a bad passwd, then ubuntu states that "Incorrect Passwd"). The only other thing I did was change my background image.

Information from my auth.log:

Apr 29 16:00:56 jj-home lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm gnome-keyring-daemon[2449]: couldn't set environment variable in session: The name of the org.gnone.SessionManager was not provided by any .service files gnome-keyring-daemon[2449]: g_dbus_connection_real_closed: Remote peer vanished with error: Underlying GIOStream returned 0 bytes on an async read (g-io-error-quark, 0). Exiting. lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm
Braiam
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Martin Kenley
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2 Answers2

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This is a known bug with lightdm. There are ways to possibly fix it, along with ways of working around the problem. Make sure your computer is connected to the internet and enter a TTY by pressing Ctrl + ALT + F2. Log in here, then try the following:

  1. Purge and reinstall lightdm:
    Run sudo apt-get remove --purge lightdm. Once that's done, run sudo apt-get update and then sudo apt-get install lightdm && sudo dpkg --configure lightdm.
  2. Reconfigure lightdm:
    I've never had much much luck with this, but you might.
    Run sudo dpkg-reconfigure lightdm.
  3. Install another Display Manager, such as gdm:
    Run sudo apt-get install gdm.
    When you are asked which Display Manager to use by default, choose gdm.

Reboot after all of these.

TheWanderer
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  • When I try to install lightdm, I get the following error: dpkg: error processing package alien (--configure): package alien is not ready for configuration, cannot configure (current state is 'half installed') – Martin Kenley Apr 30 '15 at 00:33
  • @MartinKenley Alien? OK. Try running sudo apt-get remove --purge alien and then sudo apt-get install alien before the other commands. – TheWanderer Apr 30 '15 at 00:47
  • Anyway I continued with the other steps since it said that lightdm was installed. Now when I rebooted, and choose Ubuntu from Grub menu, I get a black screen. I am using a new Nvidia GTX 960 video card. – Martin Kenley Apr 30 '15 at 00:48
  • What commands (all of them exactly) did you run? – TheWanderer Apr 30 '15 at 00:53
  • sudo apt-get remove --purge lightdm. sudo apt-get update a sudo apt-get install lightdm && sudo dpkg --configure lightdm. sudo dpkg-reconfigure lightdm. sudo apt-get install gdm. – Martin Kenley Apr 30 '15 at 00:55
  • OK. In the GRUB menu, choose Advanced Options for Ubuntu and choose a Recovery kernel from there. In the next options, choose root. Once the prompt comes up, type mount -o rw,remount /. Next, run dpkg-reconfigure gdm and choose it as the default again. – TheWanderer Apr 30 '15 at 00:57
  • OK - passed the black screen. But still in a loop as regards the login. I tried all of these and rebooted, still no luck. sudo chown root:shadow /etc/shadow sudo chown root:shadow /etc/shadow- sudo chown root:shadow /etc/gshadow sudo chown root:shadow /etc/gshadow

    Check setuid permission for /sbin/unix_chkpwd: sudo chown root:shadow /sbin/unix_chkpwd sudo chmod g+s /sbin/unix_chkpwd

     – Martin Kenley Apr 30 '15 at 01:32
  • So you're at a login screen now? – TheWanderer Apr 30 '15 at 01:32
  • Even gdm kicks you back? The login screen should look completely different. – TheWanderer Apr 30 '15 at 01:37
  • Sorry - to be clear, I had to change it back to lightdm to get avoid the black screen. If I change to gdm, I continue to get the black screen. Do you think lightdm is causing the loop in the login? – Martin Kenley Apr 30 '15 at 02:29
  • It is a known lightdm bug. – TheWanderer Apr 30 '15 at 02:29
  • Sorry, been a long day - will attempt the switch again to gdm. Thanks for the assist! – Martin Kenley Apr 30 '15 at 04:35
  • Once I switch to gdm using the steps below, ubuntu boots into a black screen. I get the ubuntu splash screen with 4 dots, then black screen.

    In the GRUB menu, choose Advanced Options for Ubuntu and choose a Recovery kernel from there. In the next options, choose root. Once the prompt comes up, type mount -o rw,remount /. Next, run dpkg-reconfigure gdm and choose it as the default again.

     – Martin Kenley Apr 30 '15 at 20:25
  • Maybe try kdm or sddm. – TheWanderer Apr 30 '15 at 20:36
  • kdm throws me into the same login loop (at login, enter user and pwd) and never gets passed this. Haven't tried sddm yet. I am able to use ctr alt F1 and login at cmd prompt. – Martin Kenley Apr 30 '15 at 20:51
  • Installing and choosing Xubuntu finally allowed me to get back to a desktop. Thanks for helping - the cmds you showed me were and will be very useful. – Martin Kenley Apr 30 '15 at 21:26
  • Are you OK with Xubuntu? – TheWanderer Apr 30 '15 at 21:42
  • Because you can try reinstalling ubuntu-desktop and unity. – TheWanderer Apr 30 '15 at 21:44
  • I would prefer to get back to ubuntu / unity. I assume steps are the ones you outlined above for lightdm and gdm? But what is the ubuntu/unity package name? – Martin Kenley Apr 30 '15 at 21:54
  • I gave them in my comment: purge and reinstall unity and ubuntu-desktop. It's risky, but you can also try putting a * after ubuntu-desktop. – TheWanderer Apr 30 '15 at 21:56
  • Thanks. I might wait it out since I need it up and running to get work done. Once a patch is rolled out, and I update (while using Xubuntu), will I pick up the patch for lightdm? Or would I have to do something to get the fix? – Martin Kenley Apr 30 '15 at 22:04
  • This bug has been around for a while, and is caused by a lot of things, so there's no likely fix. Just try the purge and reinstall of the packages. That's perfectly safe. – TheWanderer Apr 30 '15 at 22:06
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I had the same problem after the latest update. I fixed it by disabling the secure boot in the bios .. a few other people have had the same problem.

andrew.46
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Moses S
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