What to do if you encounter a Checksum mismatch error in Flatpak

The Checksum mismatch error may occur in Flatpak when installing or updating an application. The error indicates that the checksum of what it downloaded is different from what was expected – in other words, the download is probably corrupted or incomplete. Flatpak is smart enough to avoid installing the app or update when it can’t verify the integrity of the files it retrieved, and will issue an error message instead.

You can ordinarily just try updating the application again, or waiting until your internet connection is more stable. If you still receive the same error, then there are a few troubleshooting steps you can take in order to resolve the issue. In this tutorial, we will explore several causes of the Checksum mismatch error and show some troubleshooting steps that you can take to get your Flatpak tool installing apps and updates correctly again. Follow along with the step by step instructions below on your Linux system to get Flatpak working again as intended.

In this tutorial you will learn:

  • How to update all Flatpak apps with root permissions
  • How to check Flatpak installation for errors
  • How to remove unused depedencies in Flatpak
  • How to install updates via local files
  • How to check for connectivity issues
  • How to restart the Flatpak system service
What to do if you encounter a Checksum mismatch error in Flatpak
What to do if you encounter a Checksum mismatch error in Flatpak
Software Requirements and Linux Command Line Conventions
Category Requirements, Conventions or Software Version Used
System Any Linux distro
Software Flatpak package manager
Other Privileged access to your Linux system as root or via the sudo command.
Conventions # – requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
$ – requires given linux commands to be executed as a regular non-privileged user

What to do if you encounter a Checksum mismatch error in Flatpak

Run through the step by step instructions below for help in resolving the Checksum mismatch error message in Flatpak. Since there could be multiple causes for the error, we will go through several troubleshooting methods. One of them should definitely work for you.

  1. The most common cause of the Checksum mismatch error is that your connection to the Flatpak remote is not stable enough to complete a download without errors. The issue could either be on your network, the remote’s network, or some routing in between. It is advisable to simply wait some time and then try updating again. You should update all Flatpak apps at once, and with root permissions:
    $ sudo flatpak update

    You can also try adding the verbose flag to get more output related to the update process:

    $ sudo flatpak update -v
  2. If the application is still having trouble with being updated, check that your installed Flatpak version and runtimes have not been corrupted:
    $ sudo flatpak repair
  3. With the --no-pull option, you can instruct Flatpak to install updates from its local file cache, rather than downloading fresh copies from the online remote. This is a good option to try when the remote is having temporary problems or to install a queued update before fetching the newest one:
    $ sudo flatpak update --no-pull
  4. If you have some lingering Flatpak dependencies, they could be conflicting with newer updates and giving a different checksum. You can run the following command to clear your Flatpak cache and get rid of all unused depedencies. Afterwards, try updating or installing the desired app once more:
    $ sudo flatpak uninstall --unused
  5. Another thing you can try is restarting the Flatpak service in Systemd, then try updating your application again.
    $ sudo systemctl restart flatpak-system-helper.service

    If you have only just installed Flatpak recently, and have not yet done a system reboot, it is also advisable to reboot your whole system and try again:

    $ reboot

Closing Thoughts

In this tutorial, we saw how to troubleshoot the Checksum mismatch error message in Flatpak on a Linux system. Most times, this just means that Flatpak is having trouble connecting to the remote repository, and can simply try again later. Other times, it could mean that your Flatpak installation needs repaired or that Flatpak needs to be restarted. In some cases, it could also mean that there is a bug with the application that you are trying to update. In those cases, report your findings to the app developer and to Flatpak for a fix.

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