The Best Alternatives to Docker

Containerization is a method for packaging the software code into a single executable file along with libraries and dependencies. Instances packed with this method are called containers.

Containerization has gained tremendous popularity in the past decade. The company Docker, which developed the application containerizer of the same name, contributed to this. Docker has deservedly become one of the most popular tools for packaging, delivering, and running applications in an isolated environment. However, as the industry has evolved, new tools have emerged that offer their unique features. 

In this article, we will take a look at some alternatives to Docker and discuss their differences and advantages.

Docker: advantages and disadvantages

Docker is an open-source application containerization platform. It allows you to package applications with their environments and dependencies into containers and manage them using built-in commands.

^{Source: nordicapis.com}

Below, let's look at the advantages and disadvantages of Docker to understand how it can help users and what its limitations are.

Advantages of Docker

• Application Isolation

Docker provides an isolated environment for each container. This allows you to package an application with all its dependencies into a single container that can be run on any host without affecting other containers or the host system.

• Portability

Docker containers can be easily ported between different environments. For example, a developer can create a container, test it on a local computer, and then deploy it to a server or cloud infrastructure.

• Efficient resource utilization

Docker provides efficient resource utilization of the host system, allowing you to run multiple isolated containers on a single server.

• Optimized image storage and layers

Docker uses the concept of layers to optimize container image storage. A Docker image consists of multiple layers that collectively represent the container's contents. This reduces the amount of storage data and reduces image load time.

• Rapid deployment and scaling

With Docker, it is possible to deploy an application quickly, as it takes only a few seconds to start the container. In addition, Docker integrates with orchestrators (e.g., Kubernetes), which makes it easy to scale applications and automates the container management process.

Disadvantages of Docker

• Limitations in running GUIs

Docker is designed to run applications on the isolated command line (CLI) and does not have a built-in mechanism for handling graphical application interfaces. 

• Incompatibility between platforms

Another major limitation of Docker is the incompatibility of containers between different platforms. Suppose an application is specifically designed to run in a Docker container on Windows. In that case, it will not be able to run in a Docker container on a Linux platform, and vice versa. This is because Docker containers include a variety of important dependencies, including operating system dependencies.

• Dependencies on the Docker daemon

Docker requires the Docker Daemon to be running on the host system. Without it, the user cannot create and manage containers.

Docker Alternatives

For the purpose of this article, we have chosen three tools as Docker alternatives:

• Podman;

• Containerd;

• Buildah. 

Besides these, there are such tools as ZeroVM, OpenVZ, Kaniko, and others, but we will not touch upon them today.

Podman

Podman is an open-source container engine from RedHat and one of the main alternatives to Docker. It is a command line utility with commands similar to Docker.

^{Source: developers.redhat.com}

Podman Advantages:

• Daemon absence

Podman allows you to run and manage containers without a daemon, making it an ideal choice for developers who want to avoid the potential vulnerabilities associated with a constantly running Docker daemon. It also simplifies installation and reduces system load.

• Improved security

Unlike Docker, Podman ensures that each container is isolated using rootless containers technology, which improves security when dealing with privileges. However, as of late, Docker has also added a similar feature.

• Docker CLI compatibility

Podman provides compatibility with the Docker CLI, making it more attractive to users who are already familiar with it.

Containerd

Containerd is a former part of Docker and is now a standalone solution that implements an executable environment for running containers. This tool was originally developed by Docker, but has since been taken over by the Cloud Native Computing Foundation. It offers a minimal set of features for managing images and starting and stopping containers. Containerd provides simplicity and efficiency, making it an excellent choice for the average user who wants basic features with no frills.

^{Source: containerd.io} 

Advantages of Containerd:

• High performance

Containerd was originally designed for high performance, making it an optimal choice for large projects where speed is important.

• Limited functionality

Containerd provides only a basic set of features for container management, making it lightweight and easy to use.

• Stability and community support

Containerd is highly stable and widely supported because many containerization tools use it. It has a large and active community.

Buildah

Buildah is an image creation tool from Red Hat that is often used with Podman. With it, developers can create OCI-compliant container images from scratch or based on existing ones and modify and customize them with simple commands.

^{Source: linuxhandbook.com}

Advantages of Buildah:

• Daemon absence

Like Podman, Buildah does not require a central daemon to run.

• Use of Bash scripts

Using Bash scripts, you can define a base image, install the packages and dependencies, copy files, and customize the container environment. This approach makes the Buildah image creation process more structured and automated.

• Creating images from scratch

Buildah allows users to create container images from scratch. It means that an image will not contain any pre-installed packages other than those chosen by the user. This is especially useful when absolute control over the image contents and configuration is required.

Conclusion

The choice of containerization tool depends on the specific requirements of your IT company. Docker remains a powerful and popular tool, but Podman, Containerd, and Buildah have their own features and components that can improve the performance and manageability of your containers.