How to enable non-docker actions to access docker-created files on my self hosted github actions runner? (rootless docker)

This problem can be solved by running the github actions runner as root, which somewhat reduces security.

A better solution is using rootless docker:

1. Remove docker from your system if you have previously installed it through Ubuntu's default repositories.
2. install docker from Docker's repositories as directed here (I also recommendenabling cgroupsV2, as described here) & reboot. This will give you the script in /usr/bin needed to setup rootless docker in the next step.
3. setup rootless docker as described here.
4. don't forget to run the following, so docker remains running after you logout (as described in the guide)

systemctl --user enable dockersystemctl --user start dockersudo loginctl enable-linger $(whoami)

5. Also make sure to create the rootless context as described on that same page. This will make your own docker commands and the github actions runner automatically use rootless docker.

6. install the self hosted runner: https://docs.github.com/en/actions/hosting-your-own-runners/adding-self-hosted-runners (skip if already installed)

7. re(start) the actions runner. This can by done by restarting its systemd service. Your runner should now work with rootless docker

If you're having issues with the new docker build github action using buildx, also see How to solve error with rootless docker in github actions self hosted runner: write /proc/sys/net/ipv4/ping_group_range: invalid argument: unknown