Solve Ubuntu Error: Failed to download repository information Check your Internet connection.

One of the most common error one faces while updating Ubuntu, either through Software Updater or in Terminal, is Failed to download repository information Check your Internet connection.” 

Mainly the error looks like this in the terminal:

W:Failed to fetch bzip2:/var/lib/apt/lists/partial/in.archive.ubuntu.com_ubuntu_dists_oneiric_restricted_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/in.archive.ubuntu.com_ubuntu_dists_oneiric_multiverse_binary-i386_Packages Hash Sum mismatch , E:Some index files failed to download. They have been ignored, or old ones used instead

The one shot solution to this problem which has always worked for me is to run the following commands in terminal:

sudo rm -rf /var/lib/apt/lists/* 
sudo apt-get update

I hope this quick tip helps you as well.