Login problem after upgrade to Ubuntu 14.04 (Trusty Tahr) from 12.04 (Precise Pangolin) via Terminal
So as most people know, yesterday a new LTS version of Ubuntu was released, version 14.04 code name Trusty Tahr. I upgraded to this version, but not without some complications, if you are like me who only upgrade to Long Term Support versions and you are a bit too comfortable with the terminal, well my first advice will be DO NOT upgrade directly from the terminal, use the Update Manager instead. Although complications can happen either ways, but graphically it might be better.
If you are like me, and you happen to run the command;
After running this, i simply followed the steps of normal upgrade, and it was successful with minor errors which is almost unavoidable, after restarting my system, i first i booted to the login and was still seeing 12.04, that was weird but then tried to login, i landed on a black page.
Well since at first i thought it was an issue with the unity, which probably is, i opened one of my TTY's and tried running an update and then re installing ubuntu-desktop but still the error persisted, even created a new user as though a similar problem happened in 12.04, it was a problem with the config file and creating a new user will actually resolve the issue, but not in my case.
I am an opensource guy and one of the habbit is hitting the communities, i visited the Ubuntu G+ community, asked for suggestion, obviously, at least someone have encountered the same problem as you did, well the first response i got was to backup and reload my OS, however i was a bit positive a waited a few more hours. This morning i got a response that made my breakthrough from +Matthew Rhodes who had same problem as i did and suggested an easy fix.
Since you have access to your TTY, go into one by hitting CTR+ALT+F1 then login with your credentials. After that, run this commands;
$sudo apt-get update
$sudo apt-get upgrade
Wait for it to complete the upgrade and then restart. This should fix your problem, but optionally if it doesn't, do this instead;
$sudo apt-get update
$sudo apt-get dist-upgrade
PROBLEM You might encounter a minor error and you can't run apt utility with an error saying, "unmet dependencies" you can resolve this with