Sometimes after a partial upgrade of Ubuntu you suddenly find that it has broken down the System Dependency Tree and now you are unable to revert back the changes.In such cases there is a very simple command that reinstalls all the distribution packages and reconfigures them automatically.
sudo dpkg-reconfigure -phigh -aSince this command would take a lot of time to process (~1 hour) depending on your hardware in case you have a minor dependency problem you can fix it via
sudo apt-get install -f
