docker.service failed.

When the `docker.service` fails, it means that the Docker daemon is not running or cannot be started. Here are a few steps you can try to resolve the issue:

1. Check the status of the `docker.service` by running the command `systemctl status docker.service`. This will give you more information on why the service is failing.

2. Restart the `docker.service` by running the command `systemctl restart docker.service`.

3. If the service still fails, try to remove any conflicting containers or images that are preventing Docker from starting. You can do this by running the command `docker system prune`.

4. Check if there are any errors in the Docker logs by running the command `journalctl -u docker.service`.

5. If none of the above steps work, you may need to reinstall Docker on your system.

Note: Depending on your system and configuration, you may need to run some of these commands with elevated privileges (e.g. using `sudo`).