Podman vs Docker: Key Differences and Which is Better

When it comes to containerization technologies, Podman and Docker are the two giants that often come up in conversation. Both have revolutionized how we build, deploy, and manage containers, but what sets them apart?

In this blog, we'll dive deep into a side-by-side comparison of Podman and Docker. We'll cover everything from architecture to security, performance, and compatibility.

What is Docker?

Docker has been the go-to containerization platform for developers since its inception in 2013.

It's widely used to package applications and their dependencies into containers that can run consistently across different environments. Docker consists of several components, including the Docker Engine, Docker CLI, Docker Hub, and more.

Key Features of Docker:

• Containerization Platform: Docker allows you to package applications in isolated containers.
• Docker Hub: A popular repository for pre-built images that can be pulled and used for development.
• Widely Adopted: Docker is the industry standard, and many cloud providers support it.

What is Podman?

Podman is a newer tool that aims to provide an alternative to Docker while retaining compatibility with Docker's features.

Developed by Red Hat, Podman is designed to be a daemonless container engine, which means it doesn't rely on a central daemon like Docker does.

This makes it particularly attractive for certain use cases, such as rootless containers, which don't require elevated privileges to run.

Key Features of Podman:

• Daemonless Architecture: Podman runs without a central daemon, which can lead to more flexibility in certain environments.
• Rootless Containers: Podman allows users to run containers as non-root users, enhancing security.
• Docker Compatibility: Podman aims to be a drop-in replacement for Docker, meaning it can often use the same commands and workflows.

Podman vs Docker: A Quick Comparison

Architecture

The most notable difference between Podman and Docker is their architecture. Docker uses a client-server model, where the Docker CLI communicates with a Docker daemon running as a background process. This daemon is responsible for managing containers and images.

Podman, on the other hand, follows a daemonless architecture, which means there's no central daemon. Instead, each Podman command runs in its own process. This architecture allows for more flexibility and better security in certain situations.

Pros of Docker's Architecture:

• Centralized management of containers.
• Easier to scale in large environments.

Pros of Podman’s Architecture:

• More secure due to its rootless container capability.
• More lightweight and modular.

Security

Security is a critical concern when dealing with containerized applications, and both Docker and Podman offer robust security features.

However, Podman takes security a step further with its ability to run containers as a non-root user. This eliminates the need for elevated privileges, reducing the attack surface.

With Docker, you typically need to run containers with root privileges, which can be a security risk if an attacker compromises a container.

Podman Security:

• Supports rootless containers, which limits the potential damage from security breaches.
• Uses SELinux and AppArmor profiles for container isolation.

Docker Security:

• Runs containers with elevated privileges by default, making them potentially more vulnerable.
• Docker’s security model can be improved with tools like Docker Content Trust, but it requires additional configuration.

Compatibility

One of the reasons Podman has gained traction is its Docker compatibility. Podman commands are designed to be a drop-in replacement for Docker, meaning if you're familiar with Docker's CLI, you'll feel right at home with Podman.
For example:

• docker run becomes podman run
• docker build becomes podman build
• docker ps becomes podman ps

This compatibility allows for a smoother transition for teams looking to migrate from Docker to Podman without changing their workflows.

Docker Compatibility:

• Docker has widespread support across cloud providers, CI/CD pipelines, and orchestration tools.

Podman Compatibility:

• Podman offers full compatibility with Dockerfiles and Docker Compose, making it easy for developers to switch without changing their workflows.

Performance

Both Docker and Podman offer similar performance when it comes to running containers. However, due to Podman’s daemonless architecture, it can be more lightweight and may offer faster startup times in some cases.

Podman’s process-based model means that it doesn’t need to keep a long-running background service, which can lead to a more responsive user experience. In contrast, Docker's daemon can sometimes introduce overhead in terms of memory and CPU usage.

Docker Performance:

• Docker can be more efficient in large-scale environments due to its long-running daemon.
• Optimized for distributed systems.

Podman Performance:

• Podman can offer faster start times due to its daemonless nature.
• More lightweight for smaller-scale or isolated environments.

Ecosystem and Tooling

Docker has a robust ecosystem built over the years, including tools like Docker Compose for managing multi-container applications and Docker Swarm for orchestration. Docker also integrates with popular orchestration platforms like Kubernetes.

Podman, while still developing its ecosystem, is fully compatible with Kubernetes and can be used as a container runtime in Kubernetes clusters. Additionally, Podman supports Podman Compose, a tool that mimics Docker Compose for defining multi-container applications.

Docker Ecosystem:

• Wide adoption and established tooling like Docker Compose and Docker Swarm.
• Strong support in CI/CD pipelines and cloud providers.

Podman Ecosystem:

• Growing ecosystem with compatibility for Docker Compose and Kubernetes.
• More community-driven with a focus on security and flexibility.

Ease of Use

Docker has a well-established reputation for being easy to use, with a simple and intuitive CLI. Its tooling is mature, and its documentation is extensive.

Podman, while generally user-friendly, can have a bit of a learning curve due to its daemonless and rootless architecture. However, it provides a familiar CLI for those already accustomed to Docker.

Docker Ease of Use:

• Mature, well-documented, and widely adopted.
• Simple for developers to get started with containerization.

Podman Ease of Use:

• Easier for users who need rootless containers and more security features.
• Slight learning curve for Docker users, but minimal due to command compatibility.

When to Use Podman vs Docker

Use Docker if:

• You’re already heavily invested in the Docker ecosystem.
• You need mature orchestration tools like Docker Swarm or integration with cloud providers.
• You prioritize ease of use and a large, well-established community.

Use Podman if:

• You need rootless containers for enhanced security.
• You prefer a daemonless, modular architecture.
• You want to explore an alternative to Docker without abandoning your existing Docker workflow (since Podman is compatible with Docker commands).

Container Orchestration

When it comes to managing multiple containers, orchestration is a crucial aspect. Both Docker and Podman offer ways to handle complex container deployments, but their approaches and tools for orchestration differ. Let’s explore how each handles this critical aspect of container management.

Docker's Approach to Orchestration

Docker has long been known for its integration with Docker Swarm, a native orchestration tool designed to manage a cluster of Docker engines.

Docker Swarm enables you to deploy and scale containers across multiple machines with ease.

It offers features like load balancing, automatic service discovery, and self-healing to ensure that your application containers run smoothly, even in large-scale, distributed environments.

Key Docker Orchestration Tools:

• Docker Compose: Docker Compose is a powerful tool that helps you define and run multi-container applications. With a simple YAML file, developers can specify multiple services (containers), networks, and volumes.

It’s ideal for local development, testing, and smaller-scale containerized applications. Docker Compose allows you to run all your containers with a single command, making multi-container management straightforward.

• Docker Swarm: Docker Swarm is Docker’s own native container orchestration tool. It allows you to manage a cluster of Docker nodes and containers, automatically distributing containers across the cluster for high availability and scalability.

Swarm makes it easy to deploy, scale, and manage services in production environments.

• Kubernetes Integration: Docker also integrates well with Kubernetes, the most widely used container orchestration system for larger-scale, cloud-native environments. While Kubernetes is not a Docker-native tool, Docker containers are often used as the container runtime within Kubernetes clusters.

Docker's orchestration tools are highly popular due to their ease of use, scalability, and tight integration with the Docker ecosystem.

Docker Compose is especially helpful for smaller-scale, local development, while Docker Swarm and Kubernetes provide more robust options for managing containers at scale.

Podman’s Approach to Orchestration

Podman, being a newer tool, initially did not have native orchestration capabilities.

However, its design has evolved to include compatibility with orchestration tools, making it a serious contender for managing containers in both development and production environments.

Key Podman Orchestration Tools:

• Podman Compose: Podman offers Podman Compose, a tool that mimics Docker Compose. It allows you to define multi-container applications using a YAML file, similar to Docker Compose.

Podman Compose is perfect for users transitioning from Docker to Podman, as it provides the same functionality for defining and running multi-container applications. This makes it simple for developers to manage containerized applications with ease.

• Kubernetes Integration: Just like Docker, Podman also integrates with Kubernetes. In fact, Podman can generate Kubernetes YAML files from existing container configurations, which makes it easy to use Podman containers as part of a Kubernetes-based orchestration setup.

However, unlike Docker, which requires the Docker daemon to run in Kubernetes clusters, Podman can run in a rootless mode, providing added security and flexibility.

• Systemd Integration: Podman can also be integrated with systemd, a system and service manager for Linux-based systems.

Podman’s ability to work with systemd makes it easy to manage containers as system services, allowing you to handle container lifecycles and orchestration directly through systemd’s native service management tools.

This is especially useful for containerized applications on Linux servers that need to be managed as part of the system’s service architecture.

• Rootless Containers: Podman’s unique architecture allows for rootless container orchestration, meaning users can manage containers without requiring root privileges.

This is a significant advantage for environments where security and least privilege are important, as containers can be deployed and managed by non-privileged users. This rootless capability makes Podman an attractive choice for smaller teams or developers who prioritize security.

When to Use Each Tool for Orchestration

Use Docker if:

• You require robust orchestration features like Docker Swarm or integration with Kubernetes for large-scale deployments.
• You need a mature ecosystem and tools for multi-node cluster management.
• You're already familiar with Docker's workflow and ecosystem, and prefer the simplicity of managing containers with a central daemon.

Use Podman if:

• You need to run containers without requiring a central daemon and prefer a daemonless architecture.
• You want to manage rootless containers for added security, especially in environments where security is a top concern.
• You are looking for an alternative to Docker Compose with Podman Compose, or need to integrate containers with systemd for service management.

Key Differences in Orchestration Between Podman and Docker

Daemon vs. Daemonless

One of the most significant differences is Podman’s daemonless architecture. This means that it doesn't require a central service to manage containers. This makes Podman more flexible, particularly in situations where running a central daemon may not be ideal.

In contrast, Docker relies on the Docker daemon, which is necessary for managing container orchestration. For developers and organizations looking for a simpler, more secure approach, Podman’s daemonless setup can be a key advantage.

Rootless vs. Rooted Containers

While Docker typically runs containers as the root user, Podman allows for rootless containers. This enhances security, especially in multi-tenant environments or on shared systems.

Rootless containers also provide an easier approach to orchestrating containers with less risk of privilege escalation.

Cluster Management

Docker Swarm is a comprehensive solution for cluster management. With Docker Swarm, you can deploy containers across multiple nodes, scale applications, and handle fault tolerance.

Podman, being daemonless, doesn’t have an internal orchestration tool like Swarm. Instead, Podman relies on Kubernetes or systemd for larger-scale orchestration.

Container Networking

Docker provides robust networking capabilities, including support for bridge networks, host networks, and overlay networks in Docker Swarm.

Podman also offers container networking features, but these are generally more focused on local or rootless containers. For full-scale networking and multi-node orchestration, both tools integrate well with Kubernetes.

Building and Managing Container Images

One of the key tasks when working with containers is the ability to build and manage container images. Both Podman and Docker offer tools to create, push, and pull images, but there are some key differences in how each tool operates and integrates with image registries.

Docker’s Approach to Building and Managing Images

Docker is synonymous with container image building. It's a powerful tool that allows you to easily create, manage, and distribute container images, with a well-established workflow that has become the industry standard.

Building Docker Images:

Dockerfile: Docker uses the Dockerfile to define the steps for building an image. This text file specifies a series of commands (like FROM, RUN, COPY, CMD) to assemble the image from a base image. Once the Dockerfile is written, the docker build command is used to create the container image.

Docker Build Context: The build context refers to the files and directories that are available for the image build process. When running the docker build, Docker sends the context to the Docker daemon, which uses it to create the image.

Image Layers: Docker images are built in layers, meaning each command in a Dockerfile creates a new layer. These layers are cached, making the build process faster for subsequent builds if nothing has changed.

Managing Docker Images

Image Registries: Docker images are typically stored and shared through image registries. The most popular registry is Docker Hub, a public registry that hosts a vast number of official and community-contributed container images. Users can push images to Docker Hub using docker push and pull images using docker pull.

Private Registries: Docker also supports private registries for teams and organizations that require more control over their images. This allows you to store images securely within your own infrastructure or cloud service.

Tagging and Versioning: Docker images are tagged with a version, which makes it easy to manage multiple versions of the same image. Tags are typically used for different versions (e.g., myapp:v1.0 and myapp:v1.1), allowing you to reference the correct version when running containers.

Tools for Managing Docker Images:

Docker CLI: The Docker Command Line Interface (CLI) is the most commonly used tool for interacting with Docker images. You use commands like docker build, docker push, docker pull, docker images, and docker rmi to build, manage, and delete images.

Docker Desktop: For developers who prefer a graphical user interface, Docker Desktop provides an intuitive UI to manage Docker images, containers, and networks without relying on the command line.

Docker’s image-building and management features are highly robust, and its integration with Docker Hub makes it easy to share and access container images globally.

Podman’s Approach to Building and Managing Images

Podman shares many similarities with Docker when it comes to building and managing container images. Podman was designed to be Docker-compatible, so users familiar with Docker can transition smoothly.

Building Podman Images:

Podmanfile: Like Docker, Podman uses a Podmanfile (similar to a Dockerfile) to define the steps for building an image. This file works in the same way as a Dockerfile, with commands such as FROM, RUN, COPY, and CMD used to construct the image.

Build Context: Podman also uses a build context similar to Docker. You specify the files and directories needed for the build, and the build context is passed along to Podman to create the image.

Image Layers: Just like Docker, Podman images are built in layers, with each command in the Podmanfile creating a separate layer. Podman also supports image layer caching to speed up subsequent builds.

Managing Podman Images:

Image Registries: Podman can interact with Docker Hub and other container image registries just like Docker. It supports pulling and pushing images using the standard docker:// or podman:// protocols. This means you can pull images from Docker Hub or push images to private registries without any compatibility issues.

Private Registries: Podman allows you to push and pull images from both public and private registries. Users can authenticate to registries using podman login, ensuring secure access to private images.

Tagging and Versioning: Podman supports tagging images the same way Docker does. This makes it easy to version your images, whether you're working with a local build or a shared image in a registry.

Tools for Managing Podman Images:

Podman CLI: The Podman Command Line Interface (CLI) is very similar to Docker’s CLI, and many Docker commands (such as podman build, podman pull, podman push, podman images, podman rmi) are functionally equivalent to their Docker counterparts.

Podman Desktop: For users who prefer a GUI, Podman Desktop is a graphical tool that provides an easy-to-use interface to manage containers, images, and other container resources on your machine.

Podman in Rootless Mode: One unique feature of Podman is its ability to run in rootless mode, meaning you don’t need elevated privileges to build or manage container images. This is a security feature that allows individual users to create and manage containers without requiring root access.

Key Differences in Image Building and Management

Daemon vs. Daemonless: Docker relies on a central Docker daemon to manage containers and images, meaning all image-building and management operations are handled by this background service.

Podman, on the other hand, operates daemonless, meaning it doesn’t require a central service to manage containers and images. This can result in improved security and less system resource consumption when using Podman.

Rootless Containers: Podman’s ability to run in rootless mode allows users to build and manage images without needing root privileges, making it a more secure choice in environments where security is a priority.

Docker, however, requires root access to manage containers and images unless configured differently.

Dockerfile vs. Podmanfile: While the Dockerfile is the default for Docker, Podman uses a Podmanfile to build images, which is functionally the same but with a different name.

This means that a Dockerfile is fully compatible with Podman without any changes, and vice versa.

Tooling Compatibility: Since Podman was designed to be Docker-compatible, most Docker-related tools, like Docker Compose, work seamlessly with Podman (through Podman Compose).

This allows you to transition from Docker to Podman with minimal friction while retaining the same set of tools for building and managing images.

Transitioning from Docker to Podman: Process, Ease, and Resources

For many developers and organizations accustomed to Docker, transitioning to Podman can be an appealing move due to its unique benefits like daemonless operation and rootless containers.

But how easy is it to make the switch? Let's break down the transition process, covering key steps, challenges, and resources to make the move smoother.

Why Transition to Podman?

Before we talk about the transition process, let’s quickly look at why some users are considering Podman as an alternative to Docker:

• Daemonless Architecture: Podman runs without a central daemon, meaning there’s no background service running with elevated privileges. This offers enhanced security, particularly for environments that prioritize rootless operations.
• Rootless Containers: Podman allows users to run containers without needing root access, which reduces the risk of container-related security vulnerabilities.
• Docker-Compatible Commands: Podman was designed with Docker compatibility in mind. Many of the Docker CLI commands are directly supported by Podman, making the transition much easier.

If these benefits align with your goals, the good news is that transitioning from Docker to Podman is relatively simple. Let’s look at how you can make the move and what to expect along the way.

The Transition Process: Docker to Podman

1. Install Podman
The first step is installing Podman on your system. Podman is available for Linux, macOS, and Windows, and installation is straightforward.

On most Linux distributions, you can install Podman directly from the system's package manager (e.g., apt, dnf, brew On macOS).

Installation guides are available on the official Podman website, and the process is well-documented for all major platforms.

2. Replace Docker Commands with Podman
The main reason transitioning to Podman is easy is its Docker compatibility. Most Docker commands can be directly replaced with their Podman equivalents. For example:

• docker build becomes podman build
• docker pull becomes podman pull
• docker push becomes podman push
• docker run becomes podman run
• docker ps becomes podman ps
• docker stop becomes podman stop

If you're familiar with Docker, using Podman will feel almost identical, allowing for a smooth transition.

3. Managing Containers Without Docker Daemon
One of the major differences between Docker and Podman is that Podman operates daemonless. Docker relies on a central daemon that manages containers, but Podman doesn’t require a background service running, which simplifies its architecture.

As a result, Podman commands are executed in a more lightweight manner, and containers are managed per user session without the need for administrative privileges. This can be especially useful in environments where security is a concern.

4. Managing Images
Images are managed similarly in both Docker and Podman. You can pull, build, tag, and push container images using the same commands.

If you’ve already been using Docker Hub, you can continue to pull from and push images to Docker Hub using Podman without any changes.

Podman also supports private registries and can work with registries like Quay, GitHub Container Registry, or even your self-hosted solutions.

5. Podman Compose
For Docker Compose users, the good news is that Podman Compose allows you to use Compose files with Podman.

While Docker Compose is widely used to manage multi-container applications, Podman has an equivalent tool, which allows users to orchestrate multiple containers with YAML configuration files in the same way Docker Compose does.

Podman Compose works similarly to Docker Compose, so if you’ve already written docker-compose.yml files for your project, you can use them directly with Podman Compose.

6. Systemd Integration
One of Podman’s standout features is its systemd integration. Podman can generate systemd unit files that allow users to run containers as system services.

This means you can run your containers with the same management features you would use for a regular service on Linux.

This is especially useful for automating container deployment and management, and it can simplify operations for users who prefer to work with systemd.

Challenges to Watch Out For

Although transitioning from Docker to Podman is generally smooth, there are a few things to keep in mind:

• Missing Features: While Podman supports many Docker features, it doesn't yet have full compatibility with Docker Compose in all scenarios. For complex docker-compose.yml files, you might need to adjust some configurations to ensure compatibility.
• Tooling: Although Podman works well with many Docker tools, some Docker-specific tooling (like Docker Desktop or Docker Swarm) may not be supported directly by Podman. However, for most container management tasks, Podman provides adequate support.
• Learning Curve for Rootless Containers: While running containers without root privileges is a great security feature, it can introduce a learning curve, especially if you’re new to running containers in rootless mode. Understanding how this impacts file permissions, networking, and container volumes can require some experimentation.
• Podman Compose Compatibility: While Podman Compose is an excellent tool, it’s not as widely used or tested as Docker Compose. Depending on the complexity of your containerized applications, you might need to tweak some of your docker-compose.yml files for compatibility.

Conclusion

So, which one should you choose — Podman or Docker? It ultimately depends on your needs and the environment in which you're working.

Docker remains the industry standard with a broad ecosystem and great ease of use, while Podman offers an exciting alternative with enhanced security features and a more flexible, daemonless architecture.

Both tools excel at containerization, so if you’re deciding between the two, consider factors like security, ecosystem compatibility, and performance requirements.