The system cannot be started after the upgrade from Ubuntu 14.04 to Ubuntu, ubuntu12.0414.04

The system cannot be started after the upgrade from Ubuntu 14.04 to Ubuntu, ubuntu12.0414.04

Enter the Ubuntu startup interface. There are several options: Ubuntu and Ubuntu advanced...

Enter the e key to go To the grub settings page and change ro to rw.

The above can be started, temporary settings

However, to save this setting permanently, you need to go to Ubuntu and modify the file.

/Boot/grub. cfg

Change all ro files in the line similar to the following to rw.

Root = UUID = 70abcd30-1a53-4aff-acb8-25dbaefacdeab2 ro

When the Ubuntu system is upgraded to 1404LTS for login, the session always fails to be started.

Log on to the remote SSH client and run the following command to reinstall the desktop:
Sudo apt-get update
Sudo apt-get install ubuntu-desktop
Sudo apt-get-f install
Sudo dpkg-reconfigure ubuntu-desktop
Sudo reboot
Sudo apt-get install gnome-session
Sudo apt-get install lightdm
Sudo apt-get install unity-greeter

Sudo reboot

After the Ubuntu system is upgraded to 1404, after logging on to the system and entering the password, it indicates that the session fails to be started. How can this problem be solved?

Click ctrl + alt + f1 to switch to login, enter the user name and password, and then
Sudo nano/usr/share/xsessions/ubuntu. desktop
You can change the inner field to the following content.
[Desktop Entry]
Name = Ubuntu
Comment = This session logs you into Ubuntu
Exec = gnome-session -- session = ubuntu
TryExec = unity
Icon =
Type = Application
X-LightDM-shorttopname = Unity
X-Ubuntu-Gettext-Domain = gnome-session-3.0

Save and exit. Restart and try again.