Trouble downloading packages list due to a "Hash sum mismatch" error

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

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

then run:

sudo apt-get update

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.

The easiest way to fix this is:

sudo apt-get clean
sudo apt-get update

The only solution that worked for me is from unix.stackexchange.

It happens because there's a known bug it apt, and the solution is to update with a different compression method, so the files load correctly and the checksum succeeds.

Give this a try:

sudo rm -rf /var/lib/apt/lists/partial
sudo apt-get update -o Acquire::CompressionTypes::Order::=gz

(thanks @brook_hong from the comments for the rm part)

I still had the problem after removing the directories and doing sudo apt-get update.
Only the following step solved my problem:

sudo sed -i -re 's/\w+\.archive\.ubuntu\.com/archive.ubuntu.com/g' /etc/apt/sources.list

I don't know if this is the right way of fixing it...
I've found the solution here.

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?

If you're behind a proxy, then create a file named 99fixbadproxy in /etc/apt/apt.conf.d/:

sudo gedit /etc/apt/apt.conf.d/99fixbadproxy

Paste this into 99fixbadproxy and save it:

Acquire::http::Pipeline-Depth 0;
Acquire::http::No-Cache true;
Acquire::BrokenProxy    true;

Now run the update command:

sudo apt-get update

The accepted answer will rarely work if you have an issue with the CDN (content delivery network—the caches/mirrors around the world containing the apt lists and packages). It will work if a) you are using a PPA or local mirrors or b) have just a single mismatch to resolve.

Note: if you have the specific error message given in the log in the question above, the accepted answer should always work. But there are several other questions that have been closed as duplicates of this one where the accepted answer is insufficient.

It doesn't hurt to try, though, so start with:

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

This might be sufficient to proceed with sudo apt-get upgrade or other follow-up commands.

But if it doesn't work...

You may get "Hash sum mismatch" errors from that command, too. If this happens, run:

sudo apt-get update --fix-missing

It is possible that even this command will throw "Hash sum mismatch" errors, because the issue can come from transient network content errors. If so, continue to re-run the above --fix-missing command until it completes successfully. For example, like:

until sudo apt-get update --fix-missing; do echo trying again; done

(It should make progress with each run of apt-get update --fix-missing; if successive runs are not reducing the errors towards zero, press Ctrl-c to interrupt the loop. Then go back to the beginning of this answer with removing the contents of /var/lib/apt/lists and try again.)

After this, the update may work, but to be sure, first run apt-get clean, as so:

sudo apt-get clean
sudo apt-get update

Note that if you're doing this in preparation for an apt-get upgrade, it is possible (even likely, if you had enough mismatches to require updating several times) the upgrade will fail with "Hash sum mismatch" errors of its own. If so, add --fix-missing to your upgrade command:

sudo apt-get clean
sudo apt-get upgrade --fix-missing

and try again. (apt-get upgrade with --fix-missing will also try holding back failing packages and continuing others, so you should see some additional progress from running this at least once.)

But if it still doesn't work...

Like the earlier until sudo... command, you may get some further progress by repeating this command (always preceded by the clean command above), which you can even automate with

until (sudo apt-get clean; sudo apt-get upgrade --fix-missing --yes); do echo trying again; done

but, usually, it will upgrade most of the upgradable packages the first time you run it with --fix-missing and after that get stuck on the same packages, making no further progress. At that point, you'll need to go back up to the beginning with the sudo rm -rf /var/lib/apt/lists/* and try again. It is worth trying this whole process two or three times, especially if you have dozens or hundreds of upgradable packages.

The following commands may solve your issue.

sudo rm -R /var/lib/apt/lists/partial/*

and then

sudo apt-get update && sudo apt-get upgrade

it will solve your problem. I also faced the same problem but the above commands solved the problem for me. So give them a try.

Solution reference

I had the exact same problem and all solutions provided using the terminal did not help.

For me, it was by going into:

Settings → Software & Updates → Ubuntu Software: Download from: Change Local to Main Server.

It starts reloading the repos and updating. When I enter:

sudo apt-get update

After that, there was no problem at all. I'm using Ubuntu 14.04.4 LTS.