During the Ubuntu Linux OS upgrade or update process, if your system powered off because of power failure or you shutdown the power due to the system unresponsiveness, then you will face problems like boot failure, blank screen and broken Ubuntu OS. In this tutorial we will see how to fix these type of problems during Ubuntu update. Using this method you can fix the broken update without losing your data and without reinstalling your OS.
Power on your system and in the Grub boot menu select Ubuntu, if it go to the Ubuntu login screen, then press (CTRL+ALT+F1). It will open tty1 (teletypewriters) virtual terminal console. If it will not work try (CTRL+ALT+F2), (CTRL+ALT+F3), (CTRL+ALT+F4), (CTRL+ALT+F5), (CTRL+ALT+F6) and (CTRL+ALT+F7). By default in Ubuntu linux OS, there are 7 ttys.