Podman fails DIND when systemd is not available

[hlascelles]

When podman runs in container and systemd is not available, we see the error: "Error: cannot open sd-bus: No such file or directory: OCI not found".

I believe I have solved this, but because that error was not easy to find, I hope this provides a Googleable result for those that follow.

Use case:

I am running podman 3.1.2 inside a privileged ubuntu based container. Running any image results in:

# podman run ubuntu date
WARN[0000] Failed to add conmon to systemd sandbox cgroup: dial unix /run/systemd/private: connect: no such file or directory 
Error: cannot open sd-bus: No such file or directory: OCI not found

My solution so far

This has started happening since an upgrade of the base image, and diffing the invocation with podman run --log-level=debug ubuntu date I homed in on the line starting: running conmon: /usr/libexec/podman/conmon args="...

The only real difference was:

--cgroup-manager cgroupfs
# =>
--cgroup-manager systemd

So something has now changed that default. I am still trying to find out what, but that my be another story.

To debug resolve this:

1. The error is misleading, but that seems to be being addressed.
2. I followed this guidance (How to pass "--cgroup-manager=cgroupfs" in "podman-compose build"? podman-compose#209 (comment)) and added a new file (/etc/containers/containers.conf) thus:

   # /etc/containers/containers.conf
   [engine]
   cgroup_manager = "cgroupfs"
   

And now everything works.

[hlascelles]

Closing since this is now reference.