Trouble downloading updates due to “Hash sum mismatch” error

Question

When I check for updates, I get a "Failed To Download Repository Information" this is what comes up under details:

W:Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources  Hash Sum mismatch, 
E:Some index files failed to download. They have been ignored, or old ones used instead.

Answer 1

Just remove the content of /var/lib/apt/lists directory:

sudo rm -fR /var/lib/apt/lists/*

then run:

sudo apt-get update

Answer 2

This is a known issue, and is exacerbated for clients behind proxy caches. Some large organisations and ISPs (especially in remote parts of the world) have transparent caches of which you may not be aware.

The fundamental issue is that the apt repository format is subject to race conditions when a mirror is updated. This problem particularly affects repositories that change rapidly, such as the development release.

You can track progress on the fix for this in this bug (please mark yourself as "affects me too" in the bug) and this blueprint. But be aware that it is a complex issue and may take more than one release to resolve.

Answer 3

This can happen when your mirror is not up to date or serving errors from being overloaded. You can either wait a while and try again, or switch to another mirror:

• How can I get apt to use a mirror close to me, or choose a faster mirror?