Docker vs Podman: Top Differences

When it comes to Docker vs Podman, implementing a scalable, secure, and reliable DevOps ecosystem has become a DeFacto for all tech-oriented businesses. It has become a container orchestration tool that helps developers build, package, test, and deploy applications independently across all servers and OS platforms.

Having said that, selecting the right containerization tools has also become a bigger question that a solution architect/CTO of any organization has to decide while finalizing their system architecture. After all, it will impact the technology budget and the company's business overall. Taking training on Docker will help you get an understanding of docker basics, installation, and how to work with containers.

What is Docker?

Docker can be called a mammoth cargo ship holding big boxes (containers) with distinct objectives and IDs. These boxes contain unique items required to make that particular box useful for the company/person who has asked for it to be shipped. These items are first manufactured in factories that have templates to reproduce such items (I see the images). These items(images) are packaged into boxes (dockerized/containerized) to be useful for someone who has asked them to be shipped. 

Docker is open-source, virtualization software created to make a developer’s life easy. It is a kind of PaaS (platform-as-a-service) product whose core objective is to isolate virtual environments to deploy, build, and test applications that are usually incompatible or not meant to work with the current OS. 

Docker is almost a synonym for containerization amongst the developer fraternity. Docker has grown to a full-blown container solution offering everything from orchestration to load-balancing, networking, etc 

In a nutshell

Docker helps developers eliminate boring, repetitive configuration tasks and makes development fast, easy and portable across all platforms. Docker's complete ecosystem includes UIs, CLIs, APIs, and security engineered to work together across the entire application delivery lifecycle. 

Docker’s subsidiary tools handle all the tasks related to container orchestration, from load balancing to networking, making it the industry’s primary choice, besides being the established reference technology.

Why Docker? Benefits of Docker

Docker offers the following key benefits that make it an extremely reliable and useful tool for developers:

Improved and Seamless Portability  

Docker containers run without modification across any desktop, data center, and cloud environment. 

Even Lighter Weight and More Granular Updates 

With Docker containers, only one process can run in each container. This makes it possible to build an application that can continue running while one of its parts is taken down for an update or repair. 

Automated Container Creation

Docker can easily leverage code templates to craft and build a container automatically

Container Versioning  

Docker helps you track each version of any container images, and if you have to roll back any changes, you can do it seamlessly due to smart versioning support. It can even upload only the changes(delta) between an existing version and a new one. 

Docker Container Reuse  

If you have built a docker container, the same can be used as base images — essentially like templates for building new containers. 

Shared Container Libraries

Docker allows developers to create custom docker images that can be submitted to the public registry. This has helped docker to build a large public registry repo in the form of an open-source Docker hub. Developers can leverage this open-source registry to build and deploy containerized apps quickly. 

What is PodMan?

Podman (an abbreviation of Pod Manager) is Linux-native container orchestration tool that uses a daemon-less architecture to create, build and run your application. Podman containerization process is fully compliant with Open container initiatives (OCI), which it leverages to deploy your app container images and containers.

Podman container ecosystem is almost equivalent to Docker. Podman has got all the CLI and functions like docker, facilitating developers to create, maintain, modify, and run the container and their associated images in a production-ready environment 

In a nutshell

Podman: This is a tool for managing OCI containers and pods, and it leverages lib pod library that provides APIs for managing containers, pods, container images, and volumes.

Why Podman? Benefits of Podman

To understand why Podman is so powerful, we need to look into the offerings which Podman and libpod provide:

• Podman supports all kinds of container image formats like OCI and Docker images and helps you to manage the same fully.
• It provides a full container management lifecycle from creation to running, checkpointing and restoring (via CRIU), and removal. 
• Podman enables full container networking management using CNI, Netavark, and slirp4netns. 
• Podman supports pods, and container groups sharing the resources and allows Resource isolation of containers and pods. 
• It has all the support for docker-compatible CLI that can run containers both locally and remotely. 
• unlike docker, It doesn’t have a daemon manager and this choice has been made to enhance security and low resource utilization when Podman is not running.
• Podman also extends support for REST API, which can be leveraged by third-party tool to adopt Podman capabilities.
• It supports multiple OS and can run on Windows and Mac via virtual machines.
• Another concept that makes Podman special is that it is “Rootless”. This helps Podman to allow user container access without requiring us to specifically have super admin or root-level privileges. It manages the permission level stuff by using the concept of user namespaces.

Podman vs Docker: Detailed Comparison

The below table will provide you with detailed differences between Docker and Podman:

Parameters	Docker	Podman
Architecture	To create images and run containers, Docker uses a daemon-based architecture, in which an ongoing program is running in the background as an ongoing process. The Docker platform is based on a client-server logic managed by a daemon.	Podman's daemon-less architecture can run containers under the user who starts the container, so it can do everything the user does. There is no need for a mediator in Podman.
Building images	Due to Docker's self-sufficient nature, it can also build its container images as a self-sufficient tool.	As Podman cannot build containers from scratch, it requires us to use Buildah, a tool constructed specifically for running containers rather than building them from scratch.
Docker Swarm	Swarm is well suited for Docker because it works so well with Docker.	Since Docker Swarm is not supported by Podman, its commands will cause an error, and it is likely that this feature will not be included as an option for projects. There is now support for Docker Compose in Podman that provides Swarm compliance, enabling you to overcome this limitation by using Docker Compose.
Security	As Docker daemons have root privileges, attackers often use them to access your system.	Podman supports containers that don't have root privileges. It is considered that containers that do not have root privileges are safer than containers that do.
Root Privileges	The Docker community has recently included the rootless mode in its daemon configuration, but Podman was the first to use and advertise this approach as an essential capability.	Because there is no daemon to manage Podman's activity, it automatically distributes root privileges to all containers it manages on its behalf.
Pods Support	Pods are not supported by Docker.	With its name matching its function, Podman is tailor-made to create pods according to the user's needs.
Choosing Requirements	It is essential to have a robust orchestration framework that is well-documented and well-supported. In modern software development, Docker is one of the most popular tools, and with a large user community on board, you can always expect support whenever you run into problems.	A highly reliable and secure system is one of the most important things you need. Since it is a rootless and daemon-less architecture, Podman's architecture is inherently designed to be more secure than Docker's architecture.
Monolithic Platform	Docker is a monolithic platform.	Podman is not a monolithic platform.

In this section, we will try to find out some key differences between the two; having said that, the intent is not to decide the winner or loser, as both of them exist for a common reason, but to help you make a conscious decision while keeping your requirement into the consideration.

1.  Architectural Differences

• Podman is a deamonless system which is not the case with Docker. Docker uses a deamon thread called containerd. Containerd is used by docker to pull any docker images that is lying in any public or private repositories. Unlike docker Podman uses conman

Conman has a smaller memory requirement than containerd even though they delegate container creation to a low-level container runtime such as runc. 

2.  Security

Docker daemon runs with elevated root access, which is a security loophole. Rootless containers avoid this by allowing non-privileged users to run containers using user namespaces. Podman enables running and managing rootless containers, which makes it more reliable.

Do you know?

Docker recently added rootless mode to its daemon configuration, following the footstep of Podman 

3.  fork-exec

One key concept that differentiates Podman from Docker is “fork-exec”. By fork exec model, it means that Podman runs as a process initially and when the container is created it process forks and forms a separate process that constitutes what is required for the running container. 

Podman leverages fork-exec to perform in-depth user audit log in the system.

Docker uses a client-server model (using deamon process) to create containers, where the container is spawned as a child of the deamon; this makes the daemon a single point of failure. Podman does behave like this as it is deamonless. 

4.  Building Images

Docker is self-sufficient when it comes to building container images, whereas Podman relies on Buildah, which expresses its specialized nature. 

5. Pods 

Podman, matching its name, is tailor-made to create pods. Pods are a way to organize and group multiple containers under one entity name; unlike Podman, docker doesn’t support pods.

6.  Support For Docker Swarm

Many developers/organizations who rely on the docker swarm as a tool may not fall back on Podman as it does not support Docker Swarm. Though Podman has recently extended its support for docker-compose to make it compliant with a docker swarm, docker being a natural fir may pose a tough challenge.

Podman vs Docker: Which One To Choose?

You can choose Docker if: 

• You need a robust and well-documented container orchestration ecosystem. Docker is a go-to tool and with a large community, you can expect all the support available if you feel stuck somewhere while implementing it
• You are looking to implement container orchestration without hassle and with quick support. Docker swarm support makes docker stand compared to Podman as it has to rely on alternatives that are not as feature-rich as Docker Swarm or Kubernetes.

You can choose Podman if: 

• You need a highly secure and reliable system. Podman’s architecture is inherently designed to be more secure than Docker’s due to the rootless and deamon-less architecture. 
• You are looking to move to Kubernetes for your container orchestration needs later on. Podman is tailor-made to support the concept of Pod, a key object used by Kubernetes. Want to get a practical and deep understanding of Kubernetes, do try Best course for Docker and Kubernetes.

Conclusion

Can Podman be a replacement for docker? It depends. If you start with containerization tech from scratch in your company, you can start with Podman. Still, if your company is already invested heavily in the docker ecosystem, switching can be costly, so analyzing the tech debt has to be considered here.

Can docker and Podman Co-exist as an Idea? Why not? As both are OCI compliant, it is possible for both to co-exist; one can leverage docker's potential to build an app for the dev environment and to make their prod environment more secure, they can leverage Podman’s capabilities.

Docker is well suited for businesses looking to adopt a robust containerization system that is designed to be reliable and scalable and has a larger tech community to support developers. Podman should not be seen as a competition to docker but a good-to-have tool for kickstarting the containerization journey if you are just starting as an organization. Go for DevOps certification course and polish your skill.