Failed start to start session in Login – Ubuntu 15.04, Ubuntu 14.04 or Ubuntu 14.10. Ubuntu LightDM fails to start session unless user selects a session.
Here’s how to fix “failed to start session” at login in Ubuntu Systems:
First Method
Open Terminal (CTRL+ALT+T) and run the following command:
$ sudo apt-get install ubuntu-desktop
For users who have it already installed, run the command to reinstall it again:
$ sudo apt-get install --reinstall ubuntu-desktop
Once installed, restart the system. You can use the following command to restart the system or do it manually:
sudo reboot
Second Method
If the first method doesn’t work, try the second alternative method. Run the following command to reconfigure the packages:
sudo dpkg-reconfigure -a
At times, run the below command to install Gnome:
sudo apt-get install gnome-shell ubuntu-gnome-desktop
Once installed, restart the system. You can use the following command to restart the system or do it manually:
sudo reboot
This fix should resolve the session and you should be able to log in.