Podman vs Docker: Key Differences and Which One to Choose

If you’re a developer, sysadmin, or just someone curious about the containerization buzz, you’ve probably heard these names tossed around. But what’s the deal? Which one should you use? And is one better than the other? Buckle up as we explore these tools in an interactive and entertaining journey.

An Overview

Before we jump into the nitty-gritty, let’s set the stage with a brief overview of Podman and Docker. Both are powerful containerization tools that allow you to run applications in isolated environments, but they have different philosophies and ways of doing things.

Docker is the reigning champ in the containerization world, beloved for its simplicity and robust ecosystem. Podman, on the other hand, is the challenger, with a focus on security and flexibility, aiming to address some of Docker’s shortcomings.

Let’s dive into each one in detail.

What is Docker?

Imagine Docker as a magical box that lets you package up your entire application—code, runtime, libraries, and all dependencies—into a neat little bundle. This bundle, known as a container, can run consistently across any environment, be it your local machine, a cloud server, or even your friend’s laptop.

Docker was introduced in 2013 by Solomon Hykes, and it revolutionized the way we deploy applications. Before Docker, developers faced the "it works on my machine" problem—code that ran fine on one system but failed miserably on another. Docker containers solved this by providing a consistent environment for your application.

What are the Key Features of Docker?

• Containers: Lightweight, portable, and consistent across environments.

• Docker Hub: A vast repository of pre-built images.

• Docker Compose A tool to define and manage multi-container applications.

How Does Docker Work?

Let’s pop open the hood and see what makes Docker tick. At its core, Docker uses a client-server architecture:

1. Docker Client: The CLI or UI that you interact with.

2. Docker Daemon: The server that does the heavy lifting of building, running, and managing containers.

3. Docker Image: A read-only template used to create containers.

4. Docker Container: A runnable instance of a Docker image.

When you issue a command like docker run, the Docker client talks to the Docker daemon, which pulls the necessary image from Docker Hub (if it’s not already on your machine), creates a container from that image, and runs it. The container is isolated from your system but can interact with it if you allow it.

What's the Docker Role in Containerization History?

Docker is the grandfather of modern containerization. It didn’t invent containers (that honour goes to technologies like LXC and chroot), but it made them accessible and easy to use. Docker’s impact on the DevOps world is monumental, as it allowed developers to build once and run anywhere, paving the way for the microservices architecture and the rise of cloud-native applications.

What is Podman?

Podman is the cool new kid on the block. Developed by Red Hat, Podman (short for Pod Manager) is a container engine that aims to provide a more secure and flexible alternative to Docker. It’s fully open-source and designed to work seamlessly with Kubernetes.

Unlike Docker, Podman doesn’t have a central daemon process. This means no single point of failure and better security, as rootless containers become a reality with Podman.

What are the Key Features of Podman?

• Daemonless Architecture: No central daemon, enhancing security and flexibility.

• Rootless Containers: Run containers as a non-root user.

• Kubernetes Integration: Works natively with Kubernetes YAML files.

How Does Podman Work?

Podman, as mentioned earlier, breaks away from Docker’s client-server architecture. Here’s how it works:

1. Podman CLI: Similar to Docker, Podman provides a command-line interface for managing containers.

2. No Daemon: Each container is a child process of the Podman command, not a central daemon. This means if Podman crashes, your containers keep running.

3. Pod Concept: In Podman, you can run multiple containers in a group called a pod, similar to Kubernetes Pods. Containers in a pod share networking, storage, and other resources.

Podman’s rootless operation is one of its standout features. It allows you to run containers without needing root privileges, reducing the attack surface and making your system more secure.

What are the Similarities Between Docker and Podman?

Feature	Docker	Podman	Similarity
Container Runtime	Uses runc as the default runtime.	Uses runc as the default runtime.	Both use the same low-level runtime (runc) for managing containers.
Image Compatibility	Can pull and run OCI-compliant images.	Can pull and run OCI-compliant images.	Both support the same container image format, ensuring image compatibility.
Command-Line Interface	Docker CLI commands like docker run & docker pull.	Podman CLI mirrors Docker commands.	Commands are nearly identical, allowing users to switch between the two easily.
OCI Compliance	Fully adheres to OCI standards.	Fully adheres to OCI standards.	Both ensure compliance with OCI standards, enabling compatibility with Kubernetes and other tools.

Switching from Docker to Podman

Moving from Docker to Podman is a smooth transition, as Podman is designed to be compatible with most Docker commands. Here’s how I made the switch, with a real-world example to guide you:

1. Install Podman

First, I installed Podman on my system. Since I’m on Ubuntu, I used the following commands:

sudo apt update
sudo apt install podman

If you're on Fedora, you would use dnf, or if you're on macOS, you could use brew, and for windows follow the their installaiton documentation.

2. Replace Docker Commands

Podman’s command structure is nearly identical to Docker's, so I started by replacing my Docker commands with their Podman equivalents. Here’s how it worked for me:

• To run a container:
  

  podman run -d -p 80:80 nginx
  

  This replaced my old Docker command:
  

  docker run -d -p 80:80 nginx
  

• To list running containers:
  

  podman ps
  

  Which is just like the Docker command:
  

  docker ps
  

These commands worked out of the box with Podman, which made the initial switch feel almost seamless.

3. Migrate Docker Compose Files

I had several Docker Compose files managing multi-container applications. Since Podman doesn’t directly support Docker Compose, I used a tool called Podman Compose:

sudo apt install podman-compose

Here’s an example of how I migrated a simple docker-compose.yml file:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "80:80"
  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD: example

To start this with Podman, I ran:

podman-compose up

Podman Compose handles the translation and runs the containers as expected.

4. Leverage Podman Pods

One of the unique features of Podman is its pod concept, which is particularly useful if you’re moving towards Kubernetes. I grouped my containers into pods to manage them more effectively. For example:

podman pod create --name mypod -p 8080:80
podman run -d --pod mypod nginx
podman run -d --pod mypod redis

This allowed me to treat these containers as a single unit, which is a great feature when dealing with microservices.

5. Verify the Migration

Finally, I made sure everything was running smoothly by checking the status of the containers and pods:

podman ps -a
podman pod ps

This gave me confidence that the switch was successful, and everything was functioning as expected.

Switching from Docker to Podman was straightforward for me, and it might be for you too. By installing Podman, replacing Docker commands, migrating Docker Compose files with Podman Compose, and taking advantage of Podman’s pods, I managed to transition without much hassle.

Podman vs Docker: Use Cases

When it comes to practical applications, both Podman and Docker shine in different scenarios. Here’s how they stack up:

1. Development and Testing

   Docker has been the go-to tool for developers for years, thanks to its simplicity and extensive ecosystem. It’s perfect for quickly spinning up environments that mirror production, making development and testing a breeze. Docker Compose allows you to define and manage multi-container setups, which is essential for testing complex applications.

   However, Podman is quickly gaining traction, especially in environments where security and rootless operation are paramount. Podman’s ability to run containers without requiring root privileges makes it ideal for development teams concerned about security. Moreover, Podman’s pod feature allows developers to group containers that share resources, providing a more Kubernetes-like experience during development.

Key Takeaway: If security and Kubernetes alignment are critical, Podman might be the better choice for development and testing. But if you’re entrenched in Docker’s ecosystem, it remains a solid option.

1. CI/CD Pipelines

   In CI/CD pipelines, speed, automation, and security are key. Docker has long been integrated into CI/CD workflows, with tools like Jenkins, GitLab CI, and CircleCI offering native Docker support. Docker’s ability to create lightweight, consistent environments ensures that your code behaves the same way in testing as it does in production.

   Podman is a strong contender in the CI/CD space, especially with its rootless containers and daemonless architecture, reducing potential attack vectors in your pipeline. Additionally, Podman’s compatibility with Docker’s CLI and images means you can easily switch without overhauling your existing CI/CD setup.

Key Takeaway: Docker’s established presence in CI/CD makes it a safe choice, but Podman offers security benefits that are hard to ignore, especially in sensitive environments.

Conclusion

Docker remains the go-to choice for most, with over 83% of developers using it for containerization due to its mature ecosystem and widespread industry adoption. Choose Docker if you’re in a Docker-centric environment, need extensive tooling, or rely heavily on Docker Compose.

Podman, while newer, is gaining traction, especially for those prioritizing security (rootless containers) and closer alignment with Kubernetes. If you want a lightweight, daemonless alternative and value security, Podman might be your best bet.

FAQ’s

Is Podman Safer than Docker?

Podman’s daemonless architecture means there’s no single point of attack. Additionally, the ability to run containers as a non-root user makes it inherently more secure. With Docker, if the Docker daemon is compromised, the attacker could potentially gain root access to your system. Podman’s rootless mode mitigates this risk.

Why Is Podman More Secure Than Docker?

Podman’s security edge comes from several aspects:

1. No Daemon: The absence of a central daemon means there’s no long-running root process that could be exploited.

2. Rootless Containers: By running containers without root privileges, Podman limits the potential damage an attacker can cause.

3. SELinux Integration: Podman integrates seamlessly with SELinux (Security-Enhanced Linux), providing an additional layer of security.

Does Kubernetes Use Docker or Podman?

Kubernetes doesn’t care if you use Docker or Podman. Both can be used to create OCI-compliant (Open Container Initiative) images, which Kubernetes can run.

However, as of Kubernetes 1.20, Docker support was deprecated in favor of containerd (the core runtime used by Docker). Podman’s compatibility with Kubernetes makes it a solid choice for those looking to switch away from Docker.

Is Podman Slower Than Docker?

In most cases, no. Podman and Docker have similar performance profiles since they use the same container runtime (runc). However, some users report that Podman can be faster, especially when running rootless containers, thanks to its lightweight nature.