I tried to upgrade my system using
sudo apt-get upgrade but it's not upgrading. It just shows:
Do you want to continue [Y/n]? Y 0% [Waiting for headers].
Then it doesn't move forward.
Issue Solved, There was problem with some repository links in sources.list file.I was unable to get updates from google so it was freezing at starting point. After removing the entry for google updates it works fine !!!