Introduction
Containerization offers developers a way to test, build, and deploy applications in a streamlined manner. The benefits of containers include portability, consistency, efficiency, and less overhead compared to traditional VMs.
For a long time, Docker has been the most popular container management engine on the market. However, as containerization became the norm in the DevOps world, competitors like Podman emerged.
This article will compare two container management engines - Docker and Podman. It will also help you choose the right engine for your needs.
Note: Read our article to get a clear answer to how containers and VMs differ.
Podman vs Docker: Definitions
What is Docker?
Docker is a popular platform for creating, deploying, and managing containers. Docker containers allow developers to apply a system-agnostic approach to software deployment. Since Docker runs the same docker containers on any OS, containerized applications are cross-platform.
What is Podman?
Podman is a daemonless, rootless container engine developed by RedHat, designed as an alternative to Docker. The modular design allows Podman to use individual system components only when needed. Its rootless approach to container management allows containers to be run by non-root users.
Podman Vs. Docker: Comparison
In the following section, the article will go in-depth into similarities and differences between Podman and Docker.
| Docker | Podman | |
|---|---|---|
| Daemon | Uses the Docker daemon | Daemonless architecture |
| Root | Runs containers as root only | Runs containers as root and as non-root |
| Images | Can build container images | Uses Buildah to build container images |
| Monolithic platform | Yes | No |
| Docker-swarm | Supported | Not supported |
| Docker-compose | Supported | Supported |
| Runs natively on | Linux, macOS, Windows | Linux, macOS, Windows (with WSL) |
Note: If you need Podman installed, refer to our installation guides How to Install Podman on macOS or How to Install Podman on Ubuntu.
Architecture
Docker utilizes client-server architecture. The Docker daemon is a persistent background process that manages containers and maintains communication between the client and the server. The output of the docker version command shows separate sections for the client and the server versions.
Podman manages containers using the fork-exec model. Since Podman is a process and does not use the client-server paradigm, it does not require a daemon to run. Podman containers are child processes of the main Podman process. Using the podman version command shows that Podman lists only one version number.
The main unit of Podman architecture is a container. However, Podman also introduces the pod concept. Like Kubernetes pods, Podman pods are groups of one or more containers that share the same system resources. The pod consists of the main container and sidecar containers that support it.
Ease of Use
Docker features a comprehensive set of straightforward and intuitive commands. Using Docker, developers can easily create, deploy, and manage containerized applications.
Note: For a comprehensive list of Docker commands, download our Docker Commands cheat sheet.
Podman was built to seamlessly replace Docker in a software development workflow, so its commands are mostly the same as Docker's. For example, the docker pull command becomes podman pull:
Aside from Podman inheriting the ease-of-use of Docker, the similarity between the two tools also means that the migration from Docker to Podman requires little effort.
Root Privileges
Docker requires root privileges to communicate with the daemon since the daemon always runs as the root user. If a user is not a member of the docker Unix group, they must run Docker commands using the sudo command. Running Docker in rootless mode is possible but requires installing additional packages and specific storage drivers.
Podman is rootless by design. Thanks to its modular architecture, it is possible to grant different privileges to different users.
Building Images
Docker uses the docker build command to build container images from a dockerfile and a build context. The build context is a set of files specified in the dockerfile that is used in container creation.
Podman features the podman build command that works using syntax similar to docker build.
However, Podman uses Buildah, another open-source tool, to perform the building process. When podman build is executed, the buildah bud (build-using-dockerfile) command is called to emulate the docker build command.
Running Containers
When Docker receives the docker run command, it performs multiple actions:
- Checks if the image the user-specified exists locally. If not, it pulls the image from the configured registries.
- Creates a writeable container layer on top of the image.
- Starts the container.
Running containers with Podman is performed using the podman run command, which functions the same way as docker run. One of the main benefits of Podman compared to Docker is that Podman fully integrates with systemd by default. This enables Podman to run systemd within the container out of the box.
Docker Swarm and Docker Compose
Docker Swarm is a container orchestration platform used to manage Docker containers. It enables developers to run a cluster of Docker nodes and deploy a scalable application without other dependencies required.
Podman does not support Docker Swarm. However, Podman users can use tools such as Nomad, which comes with a Podman driver.
Note: To read more about Docker Swarm and compare it to Kubernetes, read Docker Swarm vs Kubernetes.
Docker Compose is a tool for managing multi-container application environments. It automates container initiation and management, which makes it useful as part of a software development life cycle (SDLC).
As of version 3.0, Podman supports Docker Compose. Previous versions of Podman did not have a way to simulate the Docker daemon necessary for Docker Compose to work, so they used less user-friendly alternatives like Podman Compose. However, Podman 3.0 introduces podman.socket, a UNIX socket that replaces the Docker daemon.
Security
Docker is, by design, considered a secure tool, especially when processes are executed by non-privileged users. Running containers in privileged mode is not recommended from a security perspective.
As with any other tool, Docker becomes even safer if users apply security best practices. Docker's security can be increased further by enabling AppArmor, SELinux, and GRSEC.
Podman's fork-exec architecture makes it an even more secure solution than Docker. The fork-exec model enables the system to correctly record the user modifying the system files, while the client-server approach used by Docker does not. Therefore, Podman allows for a more in-depth audit logging.
Rootless containers are another Podman feature that improves the overall security of the system. Being able to assign specific privileges to specific users allows administrators to have better access control to critical server components.
Note: OCI containers hosted on Bare Metal Cloud offer better performance and efficiency than those hosted on cloud VMs.
Podman vs Docker: How To Choose
Choose Docker if:
- You prefer a well-documented tool. Docker's main advantage over Podman is its widespread use. A large amount of Docker-related support available online means that searching the internet can resolve many potential issues.
- You need container orchestration support. Docker Swarm support is another important benefit of Docker. Users who want to orchestrate Podman containers have to resort to alternatives that are not as feature-rich as Docker Swarm or dive into Kubernetes, which has a steep learning curve and may prove to be too complex for simpler projects.
Choose Podman if:
- You emphasize on security. Podman's architecture is inherently more secure than Docker's.
- You plan to move to Kubernetes down the road. Podman introduces the pod concept, which makes it a good starting point for Kubernetes.
Since both Docker and Podman are OCI compliant, it is also possible to use them side-by-side. For example, Docker's robustness can be employed on development machines, while dev, int, and prod environments can benefit from Podman's increased security.
Conclusion
After reading this article, you should know more about the similarities and differences between Docker and Podman. If you are interested in working with containers, read more about monitoring Docker containers.
