Podman support - WIP

[phoozle]

UPDATE: https://github.com/phoozle/kamal_podman (I've packaged this solution up as a standalone gem)

Howdy

Podman is a daemonless engine for managing OCI containers and out-of-the-box is arguably more secure than Docker. Being daemonless it also has advantages on the management / auditing front of containers.

Here is a great article explaining the differences to Docker - Podman vs Docker Comparison

Original feature request for Podman support

Check out my initial effort here:
https://github.com/phoozle/kamal/tree/podman

I am unsure how my approach would fit into the maintainer's vision for Kamal, but for the time being I am just going for a proof-of-concept. It will be interesting to explore further the features that can be leveraged with Podman, as well as its limitations compared to Docker.

# config/deploy.yml
container_manager:
  manager: podman
  options:
    ...

It's very early days but I have successfully deployed one of my Rails apps with kamal using podman as the container manager!

I hope this serves as a starting point for further discussion around the integration of Podman in Kamal. I am hoping for some feedback from the maintainers on my approach and what the general Kamal community thinks about Podman.

Cheers

[wrb2]

Thank you! I am super grateful for this.

One thing I wonder about - there is docker or podman both on the "client side" (building and pushing the image) and on the "server side" (running the containers and the proxy). Could those be configurable separately so you can e.g. build using podman and deploy to docker or the other way around?

[phoozle]

Thanks!

What would the use cases be?
Are you concerned about having to run multiple virtual machines for Docker and Podman on a Mac?

[wrb2]

I've seen "podman on the client, docker on the server" in some places. But now that I'm thinking about it, I can also imagine the opposite scenario of people running Docker Desktop on Mac but using RedHat or some other Linux in which podman is the default.

[viktorianer]

I used Podman with a setup that allows running Docker commands as usual. This way, I could use docker run ... or even docker compose up, etc., seamlessly with Podman.

It would be great if Kamal could work this way too.

[phoozle]

so like kamal piping docker commands to the app server? Like a passthrough or something?

Podman command line is mostly on-par with Docker but with some limitations

[viktorianer]

Yes. I just used Podman locally and had the following in place: https://podman-desktop.io/docs/migrating-from-docker/managing-docker-compatibility. Additionally, I added docker compose changes on top, but they are not needed for Kamal and Docker.

[phoozle]

Just an update on this one:
I have moved development into a standalone gem https://github.com/phoozle/kamal_podman

I figure this is going to be the easier way forward to allow people to start leveraging podman for their Kamal deployments as quickly as possible.

I have just started porting over the work I did in my branch above, into this gem.