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 [...]