Since their inception, Containers have been extremely popular among Software Developers. A containerized environment allows Developers to create programs that run across various host systems.
Docker is the most popular software containerization service and comes packed with several tools like the Docker Desktop and Docker Hub. Containerd, on the other hand, is simply a Container runtime that handles Container creation and lifecycle.
Although the common view is that both utilities are interchangeable, the reality is that they are quite distinct in nature. This article will provide a detailed comparison of Containerd vs Docker and discuss the use cases of either.
Table of Contents
What is Docker?
Docker is an end-to-end Container Development tool, first released in 2013 that allows Developers to create software containers that can be deployed across various systems.
It defines commands in a Docker file which are interpreted by Docker during the Container building process. These commands define the necessary steps to set up a working environment for your project within the Container.
The Docker ecosystem includes several additional utilities like CLI, Docker Desktop, Kubernetes, etc., for a better user experience.
What is Containerd?
Containerd is an open-source Container runtime originally developed by Docker. A Container runtime sits at the heart of any container service such as Docker. It is a daemon (background) process responsible for managing Container creation tasks such as pulling images from repositories, resource and storage allocation, network creation, etc.
Docker uses Containerd as its runtime for creating Containers from images. Essentially, it acts as an interface (API) that allows users to use Containerd to perform low-level functionality. Simply put, when you run Docker commands in the terminal, Docker relays those commands to its low-level runtime (Containerd) that carries out all the necessary procedures.
Containerd VS Docker: A Head-to-Head Comparison
Although Containerd and Docker are slightly different technologies, they work in a similar fashion. However, being the main runtime, Containerd can independently perform major Docker functionalities, and this is where the differences between them become more apparent.
Docker is an independent Container management tool that hosts various tools and services to help Developers. Some of its common services include:
- Docker Desktop: A desktop application with an intuitive UI and interactive buttons to create and deploy Container images. It also allows you to configure Container resources and open Container environments inside a terminal.
- Docker Compose: Compose is a command-line utility that allows you to configure and run multiple containers simultaneously. It defines configurations such as Docker build files, external volumes, and network modes as a YAML file. These configurations can be used to initiate multiple Containers using a single command.
- Docker Hub: This is an image repository by Docker that allows you to build and upload program images for future use. It also contains various public images that you can pull and use for your programs.
All these tools improve Developer productivity significantly.
On the other hand, Containerd is a simple runtime that contains Open-Container Initiative (OCI) compliant rules to build and run a Container. Being a daemon process, it does not include any additional utilities and is only designed to manage a Container life cycle.
However, despite being created by Docker, Containerd is available independently and as a runtime service for many other Container services like Kubernetes.
Docker is a high-level API that can perform several functions with simple commands.
This basic run command searches for the Container image in the local directory. If it is not found, it, by default, searches for the image on Docker Hub. When the image is found, it pulls it and builds and deploys the container.
The Containerd CLI can also perform these actions, but you have to separately specify to pull the image (using the image URI) from a repository and then build and deploy it.
Furthermore, Docker also allows you to build Container images from `.docker` files. This file contains certain commands that tell Docker the actions it needs to perform to create a Container successfully. This Container image then sits as a blueprint of the container and can be used for building Containers on any host system.
In contrast, Containerd does not natively include any such feature. It can be used with third-party tools like buildkit to build images but cannot do it on its own. On a side note, as of Docker version 23.0, buildkit has replaced Docker's legacy builder to become the new default.
Regarding usability and experience, Docker is the clear winner. It offers a high-level interface, a modern UI, all the functionalities of Containerd, and so much more. While Containerd would be a better fit for low-level programming, Docker offers the ease, accessibility, and productivity most Developers desire.
Docker and Containerd are popular Container management tools that can build and maintain Container lifecycles. However, Docker offers a lot more functionality over the Containerd runtime.
While Containerd is only a low-level runtime, Docker is a complete Container management service that includes image-building utilities, an interface for easy accessibility, and a built-in runtime. At its heart, Docker also uses Containerd for Container management, but its additional perks, such as Docker Hub and Compose, set it apart from the latter.
Overall, Containerd can be used independently to create and manage Containers. However, its low-level commands can be challenging to understand. Docker is more user-friendly and increases Developer productivity.
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