rootless-podman-dockerfiles

Dockerfiles to build OCI images shipped with Podman container runtine in rootless mode.

I've been using these images to test how Podman behaves when running inside containers. To be more specific, I'm trying to use them to build images inside containers as an alternative to Docker in Docker (DinD).

Instructions and results are presented below.

1. Docker usage

1.1. Build a Podman image in rootless mode

cd <BASE-LINUX-FLAVOR> # e.g. fedora
docker build --rm -t rootless-podman .

1.2. Run a container

docker run -it --rm rootless-podman /bin/bash

1.3. Run a container in privileged mode

docker run -it --privileged --rm rootless-podman /bin/bash

1.4. Build image inside a container results

• Docker-managed containers: privileged mode is required to build images inside a given container and works as expected.

2. Podman usage

2.1. Build a Podman image in rootless mode

cd <BASE-LINUX-FLAVOR> # e.g. fedora
podman build --rm -t rootless-podman .

2.2. Run a container

podman run -it --rm rootless-podman /bin/bash

2.3. Run a container in privileged mode

podman run -it --privileged --rm rootless-podman /bin/bash

2.4. Build image inside a container results

• Podman-managed containers: privileged mode is required to build images inside a given container, but I receive the following error message when trying to do that:

  Error: error creating build container: The following failures happened while trying to pull
  image specified by <IMAGE-NAME> based on search registries in /etc/containers/registries.conf:
  
  * "localhost/<IMAGE-NAME>": Error initializing source docker://localhost/<IMAGE-NAME>: error
  pinging docker registry localhost: Get https://localhost/v2/: dial tcp 127.0.0.1:443: connect:
  connection refused
  
  * "docker.io/library/<IMAGE-NAME>": Error committing the finished image: error adding layer with
  blob "sha256:997...": Error processing tar file (exit status 1): there might not be enough IDs
  available in the namespace (requested 0:42 for /etc/gshadow): lchown /etc/gshadow: invalid
  argument
  
  * "quay.io/<IMAGE-NAME>": Error initializing source docker://quay.io/<IMAGE-NAME>: Error reading
  manifest <IMAGE-VERSION> in quay.io/<IMAGE-BASE_NAME>: error parsing HTTP 404 response body:
  invalid character '<' looking for beginning of value: "<...404 Not Found..."
  

3. How to contribute

Please make sure to take a moment and read the Code of Conduct.

3.1. Report issues

Please report bugs and suggest features via the GitHub Issues.

Before opening an issue, search the tracker for possible duplicates. If you find a duplicate, please add a comment saying that you encountered the problem as well.

3.2. Contribute code

Please make sure to read the Contributing Guide before making a pull request.