APT Failed to Fetch… Hash Sum Mismatch in Terminal. Failed to fetch update on Ubuntu 14.04 LTS (Trusty Tahr) and Linux Mint 17.x –This error warning produced by executing Linux command sudo apt-get update and produce some warning such as:
W: Failed to fetch us.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/binary-amd64/Packages Hash Sum mismatch
W: Failed to fetch us.archive.ubuntu.com/ubuntu/dists/trusty-updates/multiverse/binary-amd64/Packages Hash Sum mismatch
W: Failed to fetch us.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/binary-i386/Packages Hash Sum mismatch
W: Failed to fetch us.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/binary-i386/Packages Hash Sum mismatch
W: Failed to fetch us.archive.ubuntu.com/ubuntu/dists/trusty-updates/multiverse/binary-i386/Packages Hash Sum mismatch
W: Failed to fetch us.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/i18n/Translation-en Hash Sum mismatch
W: Failed to fetch us.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/i18n/Translation-en Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old ones used instead.
Error Reason for Trouble downloading packages list due to a “Hash sum mismatch”
This is the race conditions, your local repo cache can get into an inconsistent state; 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.
[SOLUTION] APT Hash Sum Mismatch
The solution for “Hash sum Mismatch” is to delete local repository and apt-get update will refresh the whole thing from source. To do this you need to execute these command from Terminal:
sudo rm /var/lib/apt/lists/* -vf
sudo apt-get update
If you remove all files, you have to download them again. You can just remove the invalid file to make this process faster.
Another solution was to switch repositories (eg, from us.ubuntu.com to XX.ubuntu.com where XX is your country code) or waiting. The best idea would be to wait a bit and retry later. Removing the lists might fix broken lists, but that’s rarely the case.