Disclaimer: This post is not originated by me. I post it here just for reason of backup.
> it’s “failed to load session”
Please open tty (virtual console, text mode only): ctrl+alt+f1
sudo apt-get update
sudo apt-get install ubuntu-desktop
sudo apt-get -f install
sudo dpkg-reconfigure ubuntu-desktop
If above wasn’t sufficient try:
sudo apt-get install gnome-session
sudo apt-get install lightdm
sudo apt-get install unity-greeter
sudo dpkg-reconfigure lightdm
## The install commands will tell self-explanatory if it’s already installed or not.
Just in case, the same can be done via recovery mode.
Press [Shift]-key right after boot to view boot menu, select recovery mode and select root shell (no need for ‘sudo’ there).
You could also view log file in either one of them in order to verify if essentials have been removed and install it again.
sudo nano /var/log/apt/history.log