Containerisation has revolutionized the world of software development, enabling applications to be easily deployed across different platforms and environments. At the heart of this technology is container runtime, which manages the lifecycle of containerised applications. One of the most widely used container runtimes is contained.
A containerd is an open-source container runtime developed by Docker and later donated to the Cloud Native Computing Foundation (CNCF). It provides a standardised interface for managing container images and runtimes, making it easier to deploy and manage containerised applications. In this article, we will explore what a container is, how it relates to Docker and Kubernetes, and why it is an essential component of the container ecosystem.
History of Docker
When Docker was released back in 2013, it didn't have an easy way to orchestrate container deployments in the cloud, it was a project that contained everything you need to build and run containers.
Some Googlers tried to find a simple solution for this. That solution became Kubernetes. Kubernetes was created to simplify the process of containerized workloads across a large number of machines.
When the Kubernetes came, It interacted with containers with the help of Docker, it just needs the functionality of running containers though. Docker introduced Dockershim to bypass the human-friendly aspects of the project. Docker launched Swarm, an alternative to Kubernetes that offered orchestration.
When Kubernetes started to grow, the limitation of its architecture was clear and the Open Container Initiative (OCI) standardized the container formats and runtimes.
This resulted in a specification that defined a container that can be used by multiple runtimes, Docker is an example of that. Docker then created a new project called Containerd which is a container runtime. It contains the functionality of executing containers, handling low0level storage, and managing image transfers.
Docker created contained and donated it to the Cloud Native Computing Foundation (CNCF) so that the container community can have the basis for creating new container solutions.
The OCI standardization means other container runtimes can be used too. With the help of Containerd, Kubernetes can access low-level "Docker" elements instead of actually using Docker.
What is Containerd?
Containerd is a container runtime that manages the process of creating, starting, stopping, and destroying containers. It simply manages the lifecycle of a container that is either hosted on a physical machine or a virtual machine.
Containerd supports the standards of the Open Container Initiative which is an open governance organization focused on container best practices. It supports a Kubernetes specification developed that allows multiple container runtimes to operate together as part of a cluster.
It can be used in Kubernetes that supports OCI to run containers on Kubernetes nodes.
The OCI
Container standards are defined by OCI and its specification of what a container should look like. Its work has been useful to facilitate the interoperability between different component technologies.
OCT prioritizes supporting the container usage experience by Docker. Docker's images must execute on the target platform without any user-defined arguments.
This OCI specification sets out an interface so the containers can run. A Kubernetes-specific abstraction called Container Runtime Interface(CRI) builds on OCI specification to enable support for interchangeable container runtimes within Kubernetes.
Kubernetes and Docker
Kubernetes doesn't handle the process of running containers, it just relies on a container runtime like Conatinerd.
Kuberneteswon't be supporting Docker as a container runtime anymore. Containerd will need to be used instead as it's an alternative runtime compatible with the OCI specifications.
This change won't affect the existing projects. Docker produces OCI-compliant images that OCI-complaint runtimes can run. The images that you've built with docker build will work with Kubernetes even after this change.
Two technologies are being considered, First is the command-line interface that is used to create and run containers and the second is the Docker runtime.
Conclusion
Containerd is a crucial component of containerisation that provides a standardised interface for managing container images and runtimes. Its relationship with Docker and Kubernetes is essential for higher-level container management systems. As containerisation continues to grow, understanding the role of containerd in the container ecosystem will be increasingly important.
Frequently Asked Questions
1. What is containerd?
Containerd is an open-source container runtime developed by Docker and later donated to the Cloud Native Computing Foundation (CNCF). It provides a standardized interface for managing container images and runtimes.
2. How does containerd relate to Docker?
Docker has transitioned to using containerd as its default runtime since version 1.11. This means that when you use Docker to manage containers, it is actually using containerd to handle the container runtime operations.
3. How does containerd relate to Kubernetes?
Kubernetes can also use containerd as an alternative to its default container runtime, CRI-O. By using containerd with Kubernetes, users can benefit from its standardized interface for managing container images and runtimes.
4. Why is containerd important for containerization?
Containerd provides a common language for container images and runtimes, making it easier to manage container environments across different platforms. It also allows for more efficient use of system resources, reducing overhead and improving scalability.
