Lately, I’ve been having few issues while trying to logging into the desktop in Ubuntu 12.04 (Precise Pangolin). It all started after I accidentally changed my admin (‘root’) password and I had to use the ‘recovery mode’ to recover it. Now I did recover the password, after that however, sometimes when logging in, after entering the password, ‘lightDM’ (that which manages the ‘login screen’) displayed the message text ‘loggin in …’, but nothing really happened and I couldn’t login into the desktop.
The thing was, I could log into the desktop using other user accounts (‘Guest’ session etc) but the one that I created while installing Ubuntu was the user account that was having this issue. I tried few things but none of it worked.
But as I had to forcefully turn off the HDD few times in the recent past, I just thought perhaps I should try to manually check the file system for errors and if it has corrupted files related to ‘LlightDM’, then it might help to fix it.
So again I used the ‘recovery mode’ in Ubuntu and ran ‘fsck’ (file system checking tool) and it worked! (at least for me).
Now this of course might not work for you at all as there could be many other reasons (there was a bug in LightDM that caused some similar problems but it seems to be fixed now ‘?’), but it might be worth trying (even if you haven’t forcefully turned off your PC). Below is what I did.
Step 1: First, after turning on your computer, at the GRUB menu list, choose that which ends with ‘(recovery mode)’ and press Enter (as shown below). This is usually the second option.
Step 2: Then after few seconds you should be greeted with another options window as shown below. From this menu, choose the option that says ‘fsck Check all file systems’.
Step 3: Then you’ll be greeted with another message, click ‘Yes’ and pres enter.
After that, everything is pretty automatic and you’ll see some terminal outputs and at the end you’ll be asked to press the ‘Enter’ key to continue. Then you’ll be taken to the above ‘Recovery Menu’ again.
Step 4: Since now everything is done, choose the option at the top called ‘resume’ and this will boot you into a normal Ubuntu desktop session. However, if your screen resolution is a bit broken, then don’t panic, it’s pretty normal.
Just try logging into the desktop using the ‘troublesome’ user account, if it works, then simply reboot your computer and then at the GRUB list, make your default selection and this time those resolution issues etc (if any) should be gone.
Again, this might non help you fix your logging issues with LightDM but it did help me and not to say the least, saved me a lot of trouble as well :). Good luck.