These are detailed steps for performing the first suggestion provided by Pilot6 in the comment section of your question.
Boot from a LiveUSB or LiveDVD
You will need the type of media you used to install Ubuntu the first time. Find this USB or DVD disk and boot to it. Once the system has booted choose the option that says Try Ubuntu.
Mount the partition where Ubuntu is installed.
You can find where Ubuntu is installed by running the Gnome Disk Utility. Type disks
in the Ubuntu launch button and click on the app.
Now look for your installation partition by clicking on one of the items on the left. Your installation will be on the /dev/sda
drive by default. So select the one that has /dev/sda
in the title bar of the application's window.
Now look at the descriptions under the Volumes section. Find the one that has Ext4 in the descript. That will be your installation partition.
Run these commands, one by one, to mount and copy the /var directory from your Live Session to your system.
Open a Terminal by typing terminal
in the Ubuntu Launch button. Click on the Terminal app.
Perform these steps in the black screen (the terminal).
1) $ sudo mount /dev/sda# /mnt
(Replace the # with the number where you have identified as the Ext4 partition
of your /dev/sda drive)
2) $ mkdir /mnt/var
3) $ sudo cp /var/* /mnt/var/
4) $ sudo umount /mnt
Now close the running apps and reboot. The system will prompt you to eject the live media.