Ubuntu apt Hash Sum Mismatch

So today I was attempting to change some things up on one of our servers and running a normal SaltStack highstate was timing out and causing the minion process to basically just hang. After some investigation looking over the logs in /var/log/salt/minion it was obvious the issue was with apt-get updating it’s package listings.

But that’s strange, this box is on Digital Ocean and they have their own local mirrors. Turns out it’s a fairly common scenario with Ubuntu + mirrors + badly configured proxies. If you’re seeing things like this in your logs:

W: Failed to fetch http://mirrors.digitalocean.com/ubuntu/dists/utopic/universe/source/Sources: Hash Sum mismatch
Failed to fetch http://mirrors.digitalocean.com/ubuntu/dists/utopic-updates/main/binary-amd64/Packages: Hash Sum mismatch
: Failed to fetch http://mirrors.digitalocean.com/ubuntu/dists/utopic-updates/universe/binary-amd64/Packages: Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old ones used instead.
E: Couldn't rebuild package cache

There is a pretty easy fix. You just need to clear our your existing apt source caches and re-update like this:

rm /var/lib/apt/lists/*
rm /var/lib/apt/lists/partial/*
apt-get update

This totally solved the issue for me. Not only unlocking/unsticking apt, but also making subsequent apt calls a touch faster. Hope this helps someone else!

Posted 04 December 2014

Frank Wiles

Founder of REVSYS and former President of the Django Software Foundation. Expert in building, scaling and maintaining complex web applications. Want to reach out? Contact me here or use the social links below.