I took the opportunity to play with podman, an interesting project started by RedHat:

What is Podman? Podman is a daemonless container engine for developing, managing, and running OCI Containers on your Linux System. Containers can either be run as root or in rootless mode. Simply put: alias docker=podman.

If you would like to have a detailed description of podman and buildah in comparison of Docker, I highly encourage you to read this great blog article on the RedHat Developers blog: Podman and Buildah for Docker users.

Podman in between the layers Image Registry and Containers/Images/Kernel.

Image reused from this blog article

Installing podman

You could follow those instructions to see how to install podman. In my case below I will install podman on Ubuntu 18.04:

. /etc/os-release
sudo sh -c "echo 'deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/x${NAME}\_${VERSION\_ID}/ /' > /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list"
wget -nv https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/x${NAME}\_${VERSION\_ID}/Release.key -O Release.key
sudo apt-key add - < Release.key
sudo apt-get update -qq
sudo apt-get -qq -y install podman
sudo mkdir -p /etc/containers
sudo curl https://raw.githubusercontent.com/projectatomic/registries/master/registries.fedora -o /etc/containers/registries.conf
sudo curl https://raw.githubusercontent.com/containers/skopeo/master/default-policy.json -o /etc/containers/policy.json

Playing with podman

podman info
podman pull alpine
# Note: What! it's working?! Yes it does! Without any Docker Host/Machine/Daemon ;)
podman images
podman run -it --rm docker.io/library/alpine /bin/sh
# Note: If you are trying to execute this command with [WSL 1](https://docs.microsoft.com/windows/wsl), [you will get that issue](https://github.com/containers/libpod/issues/4325#issuecomment-577944685). You need to run this with WSL 2.
podman ps

You could run the command podman help to see what else you could do.

Now let’s interact with a Container Registry and pushing an image there:

podman tag docker.io/library/alpine $crName/alpine
echo $crPassword | podman login $crName -u $crLogin --password-stdin
podman push $crName/alpine

Actually with podman you could easily do this in your bash environment: alias docker=podman, that’s the goal!

I now invite you to see how you could build our own OCI Container (not Docker ;)) Images, with my other blog article: buildah, a tool to facilitate building OCI container images.

Further readings

Hope you enjoyed this blog article and see how promising podman and others (actually the concept of the daemon-less container engine) are, cheers!