Managing user services by systemd in Github Actions runners is not so obvious as in your local machine. Here is what I found when I was trying to start rootless podman as a service.

Podman socket

I was playing with podman-py package and for that I needed to start a podman socket. Systems with systemd use systemctl utility to manage services, sockets, timers and other objects. Systemd can connect to the user service manager and this is important if you run podman in the rootless mode. Thus you need this command to start podman service and make it listen to a socket:

systemctl --user enable --now podman.socket
systemctl --user status podman.socket   
● podman.socket - Podman API Socket
     Loaded: loaded (/usr/lib/systemd/user/podman.socket; enabled; vendor preset: enabled)
     Active: active (listening) since Sat 2021-05-15 15:17:54 CEST; 1h 10min ago
   Triggers: ● podman.service
       Docs: man:podman-system-service(1)
     Listen: /run/user/1000/podman/podman.sock (Stream)
     CGroup: /user.slice/user-1000.slice/user@1000.service/podman.socket

May 15 15:17:54 thinkpad-t480s systemd[959]: Listening on Podman API Socket

After that you can use podman REST API and podman-py.

Github Actions runner

Although this command perfectly works on a regular system in Github Actions I got the error:

Failed to connect to bus: No such file or directory

After some googling I found that the reason is /lib/systemd/systemd --user process doesn’t run in a runner. This process is responsible for managing user services. In order to enable it you have to enable lingering for a user you logged in:

loginctl enable-linger $(whoami)

But this is not enough. Rootless podman puts its socket to this path $XDG_RUNTIME_DIR/podman/podman.sock and Github Actions environment doesn’t have $XDG_RUNTIME_DIR variable set. Let’s set it in this way:

export XDG_RUNTIME_DIR=/run/user/$UID

or you can add it to Github Actions environment like this:

- name: Set XDG_RUNTIME_DIR
  run: echo "XDG_RUNTIME_DIR=/run/user/$UID" >> $GITHUB_ENV

And there is one more problem. @eriksjolund found that loginctl enable-linger needs some time to finish and sleep 1 is needed after.

Podman service

Despite on I was able to enable podman socket using systemd facilities the implementation looks a bit hacky. Fortunately, podman can create a listening service that will answer API calls. I used this command to start the service in the background that listens to API calls in ${XDG_RUNTIME_DIR}/podman/podman.sock:

podman system service --time=0 unix://${XDG_RUNTIME_DIR}/podman/podman.sock &

References:

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