How to use and Troubleshoot Containerd?

Containerd comes with a command line tool called ctr and this tool is solely made for debugging Containerd and is not very user friendly as it only supports a limited set of features. While the ctr tool is bundled together with containerd, the ctr tool is solely made for debugging containerd. The nerdcti tool provides stable and human-friendly user experience. We don’t have to necessarily code on Containerd. In fact, We can simply use Kubernetes and Kubernetes will under the hood use Containerd and take that heavy lifting for us.

Follow along with the turotial to learn how to use Containerd’s command line tool ctr:

What Is Containerd?

Containerd in simple terms is a container runtime that is, Containerd is a software responsible for running and managing containers on a host system. It is a resource manager which manages the container processes, image, snapshots, container metadata and its dependencies. Going further, Containerd is a daemon for Linux and Windows, that manages the complete container life cycle of its host system from image transfer and storage to container execution and supervision and beyond. So basically Containerd is a complete package for the container lifecycle.

Containerd is a CNCF (Cloud Native Community Foundation) graduated project. It was the fifth project to graduate from CNCF on 2019. In this article we will learn about Containerd and why it is consider the secret hero of the cloud native world.

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What is Containerd?

With the increasing adoption of Kubernetes, Docker was moving with its own set of features and enhancements more oriented towards Docker Swarm so it became difficult for the Kubernetes community to adopt everything and also they started working on then CRI (Container Runtime Initiative) to plug other container runtimes with Kubernetes because it makes sense to have our own CRI that we can plug with the Kubernetes architecture rather than Docker because Docker has more number of features that probably we won’t need with respect to Kubernetes. This was when Containerd started to become more mature as a project and became fully contained which means it can perform tasks like the image pull, image push, task management etc....

How Containerd Works?

So basically when a request is sent to Docker, it passes the request to Containerd, which then passes the request to run c. Run c is actually running the containers by having the all the name spaces and other things that interact with the operating system. Therefore we usually say that Containerd sits between Docker and runc....

How Containerd was built?

Containerd was originally build alongside Docker, surprisingly, it wasn’t forked or inherited from the docker codebase but was created as a new project around the same time when OCI (Open Container Initiative) was formed and run c was created. it started with as specific branch where docker pulled its containary piece out and put it as a separate kind of project where more people could collaborate. Then it gradually grew in scope from a container supervisor to full runtime. it was initially a process supervisor that sat between the full Docker runtime and run c. Over the years it has grown in scope from a process supervisor to a full runtime....

How to use and Troubleshoot Containerd?

Containerd comes with a command line tool called ctr and this tool is solely made for debugging Containerd and is not very user friendly as it only supports a limited set of features. While the ctr tool is bundled together with containerd, the ctr tool is solely made for debugging containerd. The nerdcti tool provides stable and human-friendly user experience. We don’t have to necessarily code on Containerd. In fact, We can simply use Kubernetes and Kubernetes will under the hood use Containerd and take that heavy lifting for us....

Steps To Install Containerd

Step 1. Installing Containerd...

Features of Containerd

1. OCI Image Spec support...

Conclusion

In this article we discussed Containerd in a quite detailed way, Containerd is a daemon for Linux and Windows, that manages the complete container life cycle of its host system from image transfer and storage to container execution and supervision and beyond. We started with a quick intro to Containerd. Then we discussed how Conatinerd was build, how it was kept independent to Docker, how it was given to CNCF (Cloud Native Community Foundation) and how to graguated from CNCF. We then discussed how Containerd actually works. What happens is Docker API gets the request and it passes the request to Containerd, which then passes the request to run c. After that we discussed how to use ctr which is the command line interface for Containerd. At the end we discussed some important features of Containerd....

FAQs On Containerd

1. What is Containerd used for?...