Recovering Ubuntu after apt-get upgrade failed

I was trying to install Firefox 5 using these commands -

sudo add-apt-repository ppa:mozilla开发者_开发技巧team/firefox-stable sudo apt-get update sudo apt-get upgrade

The upgrade was happening, but I accidently killed the process, and Firefox 5 was up, so I didn't bother then. But the next time I restarted the system, I was stuck at the login screen. How can I recover it ?

You might have some broken packages. To check, press CTRL-ALT-F1 to go into TTY1 (note: CTRL-ALT-F7 gets you back to the GUI) and login using your credentials.

Now, run:

sudo apt-get install -f

It should give you more info about what's wrong.

Because you didn't provide any error logs or anything, we can't help you much...