An Investigation into compatibility issues between docker and podman container technologies

Abstract

Container technologies, such as Docker and Podman, have gained significant traction in modern software development due to their ability to package applications in isolated environments. Despite their functional similarities and adherence to OCI standards, Docker and Podman exhibit some functional compatibility issues that might hinder seamless transitions between the two platforms. This thesis investigates the root causes of these compatibility issues within the scope of command-level functionalities. Through a series of empirical tests and reviewing open source issues, incompatibilities in functionalities were identified. The research methodology includes examining Docker and Podman’s commands in the CLI and within a dockerfile, the same dockerfile is used in containers created by Docker and Podman respectively, observations and results were recorded.

Findings indicate that the majority of docker operations can be run by replacing the docker command with Podman. Podman is not a 100 percent replacement for docker. Features such as compose for Podman are still evolving. Flags like COPY -- link flag, HEALTHCHECK within a dockerfile are not supported by Podman. Podmans has its way of handling Health Check. Applications using Podman in its default mode should specify their ports above 1024, and because Podman does not have root access by default, volume mounting is a bit different from docker. The Open Container Initiative (OCI) enhances Docker-Podman compatibility but key differences remain, this work provides actionable insights for developers aiming to adapt or convert containerized applications between Docker and Podman containers, offering recommendations for overcoming specific compatibility challenges. The research highlights the necessity for further standardization within container ecosystems to enhance cross-platform functionality.