Docker and Podman are excellent container management engines and serve the same purpose in building, running, and managing containers.
Docker has been in the containerization market for quite some time. It has proven its worth and increased its demand in the labour market. It was first developed by Docker Inc. in 2013 and has been used by some of the biggest names in technology, such as Google and Facebook, making it the most popular container engine out there.
Now that containers have become much more popular and are being used almost everywhere, other tools like Podman appear to further improve and solve some specific problems we face with containerization.
In this Podman vs Docker comparison blog, you will learn about Podman and Docker. In addition, you will gain a better understanding of both container engines. At the end of the blog post, you will be able to decide which container engine suits you best.
Chances are you’re currently using Docker, so I’ll also explain how to migrate from Docker to Podman without having any problems in the later section of this blog about Podman vs Docker.
So, let’s get started.
What is containerization?
Containerization is a very efficient method of virtualization that is available. It makes it much easier for developers to test, build, and deploy applications at scale.
Containers and virtual machines are similar, but they are not the same. Because they are so similar, some people tend to confuse them because they do the same thing but differently.
Why Podman
vs Docker?
If we look at Google trends, we see that search interest in Podman is on the rise and increasing unprecedentedly. We are likely to see Podman become more popular in the coming years.
Source Docker
is still a leading player in the field, and I don’t think it’s going anywhere anytime soon, but the charts tell us that general interest in Docker is waning
.
Either developers are losing interest in Docker, or they’ve migrated to other software that could do its job better than Docker.
<img src
=”https://www.lambdatest.com/blog/wp-content/uploads/2022/08/Docker-1.png” alt=”Docker” /> Source
Before we get into the differences between Podman and Docker, let’s start by understanding what a container is. Some people tend to confuse the two because they both do the same thing (virtualization), but they are quite different.
Containers vs
. Virtual Machines In virtual machines
(VMs), system resources are distributed across multiple virtual machines. Virtual machines run separately and can have different operating systems.
Containers, on the other hand, only virtualize software layers above the operating system level, meaning you can have multiple virtualized environments with a single operating system. To learn more about the differences, you can read this blog, which discusses Containers vs Virtual Machines.
Containerization is the packaging of software code with only the operating system libraries and dependencies needed to run the code to create a single lightweight executable, called a container.
Why are containers important?
Containers play a considerable role in deploying applications, especially microservices. Microservices are a few small services that communicate, send, and receive data from each other.
According to the report, Netflix uses more than 1,000 microservices now. Each implemented app controls a specific aspect of Netflix’s colossal operation. For example, a microservice is only responsible for determining subscription status to provide content relevant to that subscription level.
Microservices allow teams to work on different parts of their applications separately without interfering with the work of another team. They are flexible, maintainable and easily adaptable.
Microservices design patterns have helped developers develop, scale, and maintain their projects efficiently. However, when it comes to implementation, they can face some challenges, especially in large-scale applications.
If you don’t use containers, you’ll have to write a bunch of instructions to your DevOps team to run the code on your side. This increases the number of errors that might occur in the application.
To learn more about microservices, you can check out this blog on how to test a microservices architecture application.
Challenges of not
using containers
If the DevOps team makes a mistake in following your instructions, they won’t be able to run the code on their side. So they’ll contact you, and you’ll have to find that little bug.
For example: suppose you are using MongoDB version 4.0, but for production, there was an error and version 4.1 has been installed. One of your microservices is not compatible with that specific version.
These bugs are often introduced into large-scale applications and can be difficult to debug.
As your application grows, it requires more dependencies and microservices, which will be a huge headache to manually redeploy every time something new is added.
Containerization makes this much easier. You don’t have to give instructions to your DevOps team, as the instructions are written in a Dockerfile. The container engine will automatically download and install all the dependencies that your code needs to run.
Dockerfile example Docker
will read the file and instructions and download the dependencies for that specific application, ending with a specific command to run the application. In this case, we are releasing a specific version of the official NodeJs Docker image.
These image repositories might depend on other
repositories and dependencies, and they might also depend on other dependencies on and on top. Docker will handle all that hard work in the background when building and running containers.
Since containers only use high-level software, it makes them lightweight and can be easily created, modified, and deleted.
Most container runtime systems also have a robust ecosystem. Many public container image repositories are ready to be downloaded and run.
For example, you can download the latest version of Selenium from DockerHub and run it inside a Docker container with a single command.
This will download the official Selenium Docker image from DockerHub and all the dependencies needed for it. Selenium will then run inside the Docker container.
Today, almost every large enterprise uses containerization to test, build, and deploy their applications. Containers have proven their importance in recent years, especially Docker.
What is Docker?
Docker is a platform-as-a-service (PAAS) product that uses operating system-level virtualization in small, lightweight packages called containers.
For starters, PaaS is a complete development platform and hosted in the cloud in the cloud. It enables enterprises and developers to host, build, and deploy applications.
Docker is also open source and helps developers build, deploy, run, and manage containerized applications. It uses a REST API that runs in the background to listen for requests and perform operations accordingly. This process is called a Docker (or dockerd) daemon
.
The Docker daemon is a background process responsible for managing all containers on a single host. It can handle all Docker images, containers, networking, storage, etc.
Docker uses the containerized daemon that listens for REST API requests to manage most of the work Docker does. For example, manage images, manage containers, volumes, and networks. Containerd listens on a Unix socket and exposes gRPC endpoints. It handles all tasks of low-level container management, storage, image distribution, network connection, etc.
How does Docker work?
The containerized daemon will pull the container images from the container logs. It then changes the container creation process to a low-level runtime called runc.
runc is a CLI tool for running containers on Linux according to the OCI specification.
OCI is a collaborative project hosted under the Linux Foundation and designed to set standards for containers. Container engines such as Docker, CRI-O, and containerd rely on the supported OCI to interact with the operating system and create the running containers.
It is designed to be used by higher-level container software. Therefore, the process of running a container goes from running it through the Docker daemon, packaging it, and then running it.
<img src
=”https://www.lambdatest.com/blog/wp-content/uploads/2022/08/image7-21-1-1-1.png” alt=”Docker Daemon” /> Docker image A Docker image is like a template that acts as a set of instructions for creating a
- Docker
container
. A Docker image contains application code, libraries, tools, dependencies, and other files required to run the application.
Docker volume
Let’s say you have a Docker container with a MongoDB database inside. Usually, this container stores every bit of data within the container itself.
The problem with this is that if you want to delete the container for any reason, you will lose all the data you have accumulated.
With Docker volumes, you can save the necessary information you need on the host computer. They are preferred where you want data to persist in containers and Docker services.
net Docker
A Docker network helps connect containers that can communicate with each other. So, Docker isn’t just the software for building and running containers. It is also a cloud platform for uploading and downloading your container images to the cloud.
With Docker, you can create, build, and run containers compatible with any operating system. In other words, if you have Docker on your system and your code runs on your machine, this code is guaranteed to run on another device if they have Docker installed.
To learn more about Docker and its implementation, read this blog on how to use Docker with Selenium.
A quick summary on
Docker: Docker uses a daemon which is a
- background process that listens for API requests to manage
- allows you to create and run super-lightweight containers
- multi-software based PAAS, including a cloud-hosted registry for sharing and downloading Docker images called DockerHub.
containers accordingly Docker
Docker is a
What is Podman?
Podman is a container engine similar to Docker. It is also used to develop, manage, and run OCI containers. Podman can manage the entire ecosystem of containers such as pods, containers, images, and container volumes using a library libpod.
What are capsules?
One of the key features of Podman is that it allows you to create pods. A pod is an organizational unit for containers. Pods are an essential part of the Kubernetes container orchestration framework.
You can use Podman to create manifest files that describe pods in a declarative format. Kubernetes can consume these manifest files written in YAML.
Unlike Docker, containers in Podman can run as root or non-root users. We will discuss this Podman vs Docker difference in more detail in the later section of this blog about Podman vs Docker.
Podman does not rely on a daemon to develop, manage, or run containers. Since Podman does not have a daemon to manage containers, Podman uses another service manager to manage all services and support running containers in the background called Systemd.
Systemd creates control units for existing containers or generates new ones, with Systemd suppliers can install, run and manage their container applications, as most are now packaged and delivered exclusively in this way.
Podman, with the help of Buildah, can build images without using a daemon. Buildah is a tool for creating OCI-compliant images through a lower-level core utility interface.
Like Docker
it has a CLI since the images created by Docker and Podman are compatible with the OCI standard. Podman can push and pull from container registries like Docker Hub and Quay.io.
If you’re already familiar with Docker, you can easily migrate from Docker to Podman (more on this later). You can also alias Podman to docker without having any problem alias docker=podman. This means you can use the same commands with Podman as you can with Docker.
Podman, like Docker, relies on a compatible OCI like RunC to interact with the operating system and create the running containers. Therefore, it will make Podman very similar to other container engines like Docker.
Podman
also uses the REST API that Podman provides to manage containers; this REST API is only available on Linux. To interact with this REST API, Podman has a client that is available on all major Windows, macOS, and Linux operating systems.
If the Podman REST API is only available on Linux, how can we use it on Windows or macOS?
Although the containers are Linux, Podman also runs on Mac and Windows. It provides a native Podman CLI and incorporates a guest Linux system to launch the containers.
This guest is also called the Podman machine and can be managed using the podman machine command.
A quick summary on
Podman:
- Podman helps you find containers in DockerHub or quay.io or
- from pre-built container images
- Build new layers or containers with a few adjustments
- You can easily share your container images anywhere you want with just a podman push command.
on an internal logging server. Easily run containers
.
.
Running a
Redis server inside a container using
Podman
Running containers with Podman is quite easy and similar to Docker. To do this, run the following command:
Podman will run a Redis server based on the official Redis image inside a container. The container will run in separate mode declared by -d and will be named Redis as specified by —-name.
The container will expose the ports and connect them to the same port on the host computer, which is the default Redis port as specified with -p 6379:6379.
After running the command, Podman will check to see if the Redis image already exists on the local computer. If you do, you’ll build a container based on that image. If it doesn’t, it will search for that image from DockerHub and download the latest version.
Comparison of Podman vs
Docker
Generally, Podman and Docker do the same thing. However, there are some differences between the two container engines, Podman vs Docker.
These are the main differences between Podman vs
Docker:
Architecture: Podman has a Daemonless architecture
The Docker daemon is a background process responsible for managing all containers on a single host. It can handle all Docker images, containers, networking, storage, etc. The Docker daemon uses a REST API to listen for requests and perform operations accordingly.
Therefore, Docker needs this daemon to run in the background to manage, create, run, and create containers. Docker has client-server logic mediated by the Docker daemon.
Podman, on the other hand, doesn’t need a demon. It has a (daemonless architecture), which helps users start running containers (rootless). In other words, Podman does not require root privileges to manage containers.
Root privileges
Since
Docker needs a daemon to manage its containers, it will need root permission to run the processes. Since
Podman does not have a daemon, he has one (architecture without daemon). It does not require root privileges for its containers.
Rootless execution
In the beginning, when Docker came out, you couldn’t run Docker without root permission. However, rootless mode was introduced in Docker in v19.03 and graduated from experimental in Docker Engine v20.10.
However, rootless Docker doesn’t come straight out of the box. Some third-party configurations and packages must first be installed on the host before installing Docker.
So, yes, you can run Docker and Podman as root. But it’s good to know that Podman introduced working containers in rootless, which also comes with some limitations.
Limitations
of rootless Docker The rootless
mode in Docker isn’t perfect, and some issues come with running containers with rootless Docker:
- Not being able to run containers on privileged ports, which are all ports below 1024. Otherwise, they cannot be executed.
-
- fuse-overlayfs is installed).
- btrfs (only if running kernel 4.18 or later, or ~/.local/share/docker is mounted with user_subvol_rm_allowed mount option).
- Vfs
- Cgroup is only supported when running with cgroup v2 and systemd
.
. The following features are not supported:AppArmor Checkpoint Overlay network Exposing SCTP Ports To use the ping command.
-
- IPAddress is displayed in docker inspect and is spaced within the RootlessKit network namespace. This means that the IP address is not reachable from the host without nsenter -ing in the network namespace.
- The host network (docker run -net=host) is also spaced within RootlessKit.
- NFS is mounted as the Docker “data root” is not supported. This limitation is not specific to the non-root mode.
Only the following storage drivers are supported:overlay2 (only if running with kernel 5.11 or later or Ubuntu-flavored kernel). fuse-overlayfs (only if running kernel 4.18 or later, and
Security
Does Podman have greater security than Docker? Previously, we saw how Podman can run without root because it has a (daemonless architecture), and Docker cannot run without root because it requires a daemon to run and manage the containers while comparing Podman vs Docker.
But why is this important? Why not having a daemon and being able to run containers without root privileges is essential? The answer is that we don’t grant root privileges to apps we don’t trust, and we do trust our containers and apps.
But that’s not the case. Let’s say an attacker has found a way to access one of your containers! Since Docker can only run with root privileges, any malicious actor (i.e. attacker) can perform incorrect actions on your server with those root privileges.
With Podman, if an attacker gains access to your container, they will be able to harm you, but they still won’t be able to perform actions that require root privileges. Therefore, Podman is considered more secure than Docker.
Imaging
Docker is a self-sufficient platform. It can create images and run containers on its own without the need for any other third-party tools.
Podman, on the other hand, is only designed to run containers and not build them. That’s where Buildah comes in. Buildah is an open source tool that creates Open Container Initiative (OCI) container images.
Podman, with the help of Buildah, can build your OCI container images.
Docker Swarm and docker-compose
Docker
Swarm is a container orchestration platform used to manage Docker containers. With Docker Swarm, you can run a cluster of Docker nodes and deploy scalable applications without requiring other dependencies.
Docker Swarm can also manage multiple containers on multiple hosts and connect them all. Docker Swarm can obviously be used with Docker right out of the box without any problems.
Podman
does not support Docker Swarm, but other tools can be used with Podman, such as Nomad, which comes with a Podman controller
.
Docker-compose is a tool for managing applications with multiple containers. The main difference between Docker compose and Docker swarm is that docker-compose runs only on a single host, while Docker swarm connects multiple hosts.
Docker automatically supports docker-compose and can work well with it right out of the box.
In previous versions of Podman, Podman
didn’t have a way to simulate the Docker daemon needed for Docker compose to work, so Podman compose was used
. Now, in version 3.0, Podman introduced the podman.socket, a
UNIX socket that replaces the Docker Daemon. All-in-one
vs
modular
Podman has a modular approach, which relies on specialized tools for specific tasks, while Docker is a monolithic standalone tool. Docker is a monolithic and powerful standalone tool. By monolithic, it means that Docker does not rely on any other third-party tools to manage containers, run, build, or handle any other container-related tasks.
This is a significant difference between Podman vs Docker technologies.
As we discussed, Podman relies on many additional third-party tools to achieve the same goals as dockers. For example, it uses Buildah to create container images, while Docker doesn’t need Buildah or any other third-party tools to create images.
Here is the summary of the Podman vs Docker comparison.
Docker podman uses a daemon. It has an architecture without demons. It can only run with root privileges. Capable of running without root. Less secure as all containers have root privileges. More secure since containers do not have root privileges. Docker is a self-sufficient tool and creates images by itself. Podman cannot construct images by himself. Use another tool called buildah to build images. It supports Docker swarm and Docker compose right out of the box. It does not support Docker swarm or Docker composition. Docker is a monolithic standalone tool. Podman is based on other third-party tools.
Since we’ve learned about comparing Podman vs. Docker, is it safe to consider Podman as a replacement for Docker? Let’s check this out in the next section of this Podman vs Docker blog.
Is Podman a replacement for Docker, or can they work together?
Some developers use Podman for production and Docker for development. Since both are OCI compatible, compatibility won’t be an issue. However, it is best to compare Podman vs Docker before moving forward.
You can use Docker for development to make your job easier and use Podman for production to benefit from the extra security it provides and make your application more efficient.
Podman can be a primary containerization technology option if you start a project from scratch. If the project is ongoing and you’re already using Docker, it depends on the details, but it may not be worth the effort. As a native Linux application, it demands Linux skills from the developers involved.
How to migrate from Docker to Podman?
Migrating from Docker to Podman could be fairly easy and simple to implement. The same commands you use to use Docker can also be used for Podman, so you don’t have to worry about memorizing new commands, which makes migration really easy.
Some developers simply alias Docker to Podman, and everything works the same, but the processes are handled by Podman instead of Docker.
Running a Node container.js with
Podman
First, you must have Podman installed on your computer. If you want to continue with this short tutorial, you can download the sample node.js application from this GitHub repository.
Since both Podman and Docker comply with the OCI container standard, Podman can also create containers from a Dockerfile, so if you can build and run a container from a Dockerfile with
Docker, you can also run it with Podman. Let’s create the container in this
Dockerfile: To compile the container, run the following command:
After running the command, Podman will run the Dockerfile and compile the image
on its local machine.
You can display the container images available on your local device by running podman images.
We only created an image called my-node-app, but if you notice, we have another additional image since the container we are trying to run is based on node:16. Podman will automatically download that image to run the container we want to run.
After you create the image, you can run an instance of this by running a container using the following command
: The -name tag will specify the name of the container, -p will map the port inside the container
to the port on the host machine -p host:container
.
Finally, add the localhost/my-node-app app at the end to specify the container image we want our new container to run on.
Congratulations, your server is now running on port 3000 inside a container run by Podman. You can access it from your browser.
All the commands
we used in this tutorial were the same as the Docker commands. That’s why migrating from docker to Podman is easy, and developers get used to it effortlessly.
Another interesting feature of Podman is that you can stop or remove all containers using the —-all flag. With Docker, you couldn’t have used that.
For example, if you want to stop all containers with Podman, you can run podman stop —-all. If you’re going to do the same with Docker, you have to run docker stop $(docker ps -a -q), which is a bit difficult to memorize.
Integrating Docker or Podman with Selenium Grid is easy and helps you perform Selenium automation testing. However, the capabilities offered by Selenium Grid with Docker or Podman can be further enhanced by integrating an online Selenium Grid like LambdaTest.
You can also subscribe to the LambdaTest YouTube channel and stay updated with the latest tutorials on selenium testing, Cypress E2E testing, CI/CD and more
.
LambdaTest is a cross-browser testing platform that enables you to perform manual and automated browser testing of websites and web applications across an online browser farm of 3000+ browsers and operating system combinations.
LambdaTest’s reliable, scalable, secure, and high-performance test execution cloud enables development and test teams to accelerate their release cycles. It allows you to run parallel tests and reduce test execution by more than 10 times.
Conclusion
In this Podman vs Docker blog, we’ve seen that both Docker and Podman are amazing at running and managing containers. You can build and deploy large-scale applications with both.
If you’re more concerned about security in your applications or plan to use Kubernetes to orchestrate your containers, Podman is the best choice for you.
If you want a well-documented tool with a much larger user base, then Docker is the best choice for you.
