Recovery from failed upgrade from Ubuntu 14.10 to 15.10

Why upgrade failed?

When the upgrade is ongoing, I plugged out the power and the network wire, then Ubuntu hanged and the upgrade stopped there without any response.

We know there are several steps in the upgrade process, such as downloading the packages and installing the package locally.

Since the download seems finished, I think the packages are installed in local and the network is not needed in this step.

But I was wrong.

What the consequence?

After I reboot the laptop by pressing the power button for several seconds, Ubuntu can not started into GUI normal desktop environment! And there is some error output in the command line window.

What should I do to recover Ubuntu?

recovery mode

If your system fails to boot for whatever reason, it may be useful to boot it into recovery mode. This mode just loads some basic services and drops you into command line mode. You are then logged in as root (the superuser) and can repair your system using command line tools. If booting into recovery mode does not work you can still use your installation CD (if it is a live cd) as described in LivecdRecovery.

How to enter recovery mode?

After turn on the power, and just before entering the Ubuntu, quick click the Shift button.

Commands to recover the original version of Ubuntu

sudo dpkg –get-selections | grep linux

sudo apt-get remove linux-image-3.16.0-xx-generic

sudo apt-get autoremove

sudo reboot -f

NOTE: the method here is only for reference. The command may destroy your Ubuntu.