Description: I am trying to login in my Ubuntu machine. I entered my correct password and it didn’t login me. It showed me “failed to start session” message in red color. I am also not able to login with guest user.
Solution: This problem occurs when your Unity desktop or your GUI interface Crashes. There are different way to recover.
When you are on login screen press Ctrl+Alt+F1 for GUI (Graphical User Interface) to access CLI (Command line interface). Here type username and password. You will successfully login.
Now to fix your desktop type following command:
$sudo apt-get install ubuntu-desktop
Ubuntu: Desktop package is by default Interface in Ubuntu. If it already installed try to reinstall it by this:
$sudo apt-get install --reinstall ubuntu-desktop
After reinstall reboots your system:
$reboot or sudo init 6
Alternate Method: Try some other GUI for Ubuntu gnome by using this command:
$sudo apt-get install gnome
It will install new GUI for the System.