Podman vs Docker: The fight of orchestration tools
What is Container Orchestration?
Container orchestration is the automation of much of the operational effort required to run containerized workloads and services.
Containers are lightweight, portable, and secure, providing an insulated space compatible with any environment. By separating the software from the operating system, containers can be transferred to any location (from Linux to Windows systems, for example), avoiding bugs and errors preventing them from working.
Some of the most popular orchestration technologies are Docker, Docker Swarm, Kubernetes, and Nomad.
What is Docker?
Docker is an open source tool that enables developers to build, deploy, run, update and manage containers. It is one of the most widely renowned and used tool when it comes to development with ever increasing popularity.
Image source: Stack Overflow survey 2021
It quickly became an all-in-one solution containing tools developed for specific tasks. One is Docker Swarm, a native Docker feature that lets you cluster and schedule Docker Engines, and another tool designed to create and manage a swarm of containers.
But this self-sufficiency has its shortcomings. Though it is a powerful system to create and run containers in all of its stages of development, other tools have difficulties interacting with it.
What is Podman?
Podman is an open-source, Linux-native tool designed to develop, manage, and run containers and pods under the Open Container Initiative (OCI) standards. Presented as a user-friendly container orchestrator developed by Red Hat, Podman is the default container engine in RedHat 8 and CentOS 8.
It is one of a set of command-line tools designed to handle different tasks of the containerization process, that can work as a modular framework. This set includes:
Podman — pods and container image manger
Buildah — a container builder
Skopeo — a container image inspection manager
runc — container runner and feature builder to podman and buildah
crun — optional runtime that allows greater flexibility, control, and security for rootless containers
These tools can also work with any OCI-compatible container engine, like Docker, making it easy to transition to Podman or use it with an existing Docker installation. And can Kubernetes use Podman? Yes it can. In fact, Kubernetes and Podman are similar in some ways.
Podman has a different approach to containers. As hinted by the name, Podman can create container “pods” that work together, a feature resembling the Kubernetes pods. Pods organize separate containers under a common denomination to manage them as single units.
Another defining feature of Podman is that it is daemon-less. A daemon is a program running in the background to handle services, processes, and requests with no user interface. Podman is a unique take on the container engine, as it doesn’t actually depend on a daemon, but instead launches containers and pods as child processes.
You may be thinking “Why should I use Podman?” Podman has unique advantages as a development and management tool that makes it a viable and interesting alternative to Docker in the appropriate context. Or a powerful complement to work side by side with Docker since it supports a Docker-compatible CLI interface.
Podman vs Docker:
Podman and Docker share many features in common but have some fundamental differences. These don’t make one better than the other but might be decisive to select the most appropriate for a specific project.
Architecture
Docker uses a daemon, an ongoing program running in the background, to create images and run containers. Podman has a daemon-less architecture which means it can run containers under the user starting the container. Docker has a client-server logic mediated by a daemon; Podman does not need the mediator.
Root privileges
Podman, since it doesn’t have a daemon to manage its activity, also dispenses root privileges for its containers. Docker recently added rootless mode to its daemon configuration, but Podman used this approach first and promoted it as a fundamental feature.
Security
Is Podman safer than Docker? Podman allows for non-root privileges for containers.Rootless containers are considered safer than containers with root privileges. In Docker, daemons have root privileges, making them the preferred gateway for attackers. Containers in Podman do not have root access by default, adding a natural barrier between root and rootless levels, improving security. Still, Podman can run both root and rootless containers.
Systemd
Without a daemon, Podman needs another tool to manage services and support running containers in the background. Systemd creates control units for existing containers or to generate new ones. Systemd can also be integrated with Podman allowing it to run containers with systemd enabled by default, without any modification.
By using systemd, vendors can install, run, and manage their applications as containers since most are now exclusively packaged and delivered this way.
Building images
As a self-sufficient tool, Docker can build container images on its own. Podman requires the assistance of another tool called Buildah, which expresses its specialized nature: it is made for running but not building containers on its own.
All in one vs modular
And maybe this is the crucial difference in both technologies: Docker is a monolithic, powerful, independent tool with all the benefits and drawbacks implied, handling all of the containerization tasks throughout their entire cycle. Podman has a modular approach, relying on specialized tools for specific duties.
Can Podman and Docker work together?
Sold as the best and easiest to apply alternative to Docker — users can just alias Docker to Podman (alias docker=podman) without any problems. Podman is a more than capable tool for containerization tasks.
Is Podman a replacement for Docker?
Podman can be a primary containerization technology option if you are starting a project from scratch. If the project is ongoing and already using Docker, it depends on the specifics, but it might not be worth the effort. As a Linux native application, it demands Linux skills from the developers involved.
Developers can combine both tools by relying on Docker in the development stage and later push the project to Podman in runtime environments, benefitting from the added security it provides. And since they’re both OCI-compliant, compatibility shouldn’t be a problem.
Can Docker and Podman coexist? Yes, and quite well. Many developers have been using Docker and Podman in tandem to create safer, more efficient, agile frameworks. They have a lot in common, making the transition from Docker to Podman or their combination quite seamless.
Hope you are now well aware of the similarities and differences between Docker and Podman.
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