examples: add {docker,podman,singularity}.yaml

[AkihiroSuda]

Docker, Podman, Singularity, or whatever can be used instead of the default containerd/nerdctl .

LXD can be used too, of course, but there is no lxd.yaml, because LXD is included in the default Ubuntu image.

Example usage:

$ limactl start ./docker.yaml
$ limactl shell docker docker run -it --rm -v $HOME:$HOME alpine

$ limactl start ./podman.yaml
$ limactl shell podman podman run -it --rm -v $HOME:$HOME:ro docker.io/library/alpine

$ limactl start ./singularity.yaml
$ limactl shell singularity singularity run -u -B $HOME:$HOME docker://alpine

---

docker CLI on macOS can connect to dockerd inside the guest VM as well: DOCKER_HOST=ssh://127.0.0.1:60006 docker run -it --rm -v $HOME:$HOME alpine .

This requires NoHostAuthenticationForLocalhost yes in ~/.ssh/config. (Alternatively you can just login to ssh -p 60006 127.0.0.1 to initialize ~/.ssh/known_hosts)

[csantanapr]

podman on macos doesn't support volumes -v so this solution would be perfect.

[jandubois]

The DOCKER_HOST=... examples only work when rebasing on top of #220. Sorry about the breakage! 😞

I suspect there are various ways this could also be broken by .ssh/config settings. I think we should support forwarding sockets in addition to ports from the host agent; that way it could even be linked to the default socket location. See e.g. https://github.com/abiosoft/colima/blob/main/colima#L151

I've tried all the sample commands, and they all work for me.

Have not yet found time to review the example files themselves.