CNCF: Containerd C ontainer orchestration and management have become the backbone of modern software development, making tools lik...
Container orchestration and management have become the backbone of modern software development, making tools like Containerd a crucial part of the ecosystem. But what exactly is containerd, and why is it gaining popularity? This blog will explore what containerd is, its features, and how it fits into the containerization landscape
At the beginning of the container Era, Kubernetes supported only Docker. After some years other container runtime also supports by Kubernetes.
Kubernetes introduced the Container Run-time interface Called CRI-(container run Time Interface(CRI) so that any container runtime follows the OCI(open container initiative) standards that can support Kubernetes.
What is Containerd?
containerd is an open-source container runtime that manages the complete lifecycle of containers. Originally developed by Docker, it is now a Cloud Native Computing Foundation (CNCF) project. It is designed to be a lightweight, reliable, and efficient runtime, providing core functionality for managing containers without the overhead of additional orchestration features.
Containerd acts as the glue between the operating system and container orchestration platforms like Kubernetes, handling tasks like:
- Container execution
- Image transfer and storage
- Snapshot management
- Low-level storage and network management
Why Choose Containerd?
Containerd is a preferred runtime for many developers and organizations due to its simplicity and robustness. Here are some key reasons why:
1. Simplicity
Unlike full-fledged container platforms, containerd focuses solely on container lifecycle management. This makes it lightweight and easy to integrate with other tools like Kubernetes and Docker.
2. Performance
With its minimalist design, containerd provides fast container startup times and efficient resource usage, making it ideal for high-performance environments.
3. Industry Standard
Being a CNCF graduate project, containerd is widely supported and adopted across the industry. It powers major platforms like Docker and Kubernetes (via CRI-O).
4. Extensibility
Containerd supports plugins, allowing developers to extend its functionality to meet specific use cases, such as custom storage or networking solutions.
5. Security
By adhering to open standards like the Open Container Initiative (OCI), containerd ensures secure and consistent container behavior across environments.
Core Features of Containerd
1. OCI Compliance: Fully supports OCI standards for images and runtimes.
2. Snapshot Management: Manages filesystem snapshots for container storage.
3. Pluggable Architecture: Integrates easily with external tools for extended functionality.
4. Cross-Platform Support: Works on Linux, Windows, and macOS.
5. gRPC API: Offers a robust gRPC API for automation and integration with orchestration tools.
Containerd vs Docker
It’s common to confuse containerd with Docker since Docker initially developed it. However, they serve distinct roles
How Containerd Fits into Kubernetes
Kubernetes uses container runtimes to manage the lifecycle of pods and containers. containerd is one of the most popular runtimes for Kubernetes, often configured using the Container Runtime Interface (CRI).With its lightweight nature, containerd integrates seamlessly with Kubernetes, providing:
1. Efficient container creation and deletion.
2. Robust image pulling and storage.
3. Support for container snapshots and checkpoints.
Getting Started with Containerd
To start using containerd, you can install it on your Linux-based systems
# Install containerd
sudo apt-get update && sudo apt-get install -y containerd
# Start the containerd service
sudo systemctl start containerd
sudo systemctl enable containerd
Containerd has cli tools similar to a Docker-cli
It is used for debugging the containerd and limited features
Ctr CLI is included with containerd by default.
To verify whether it’s installed or not run the below command
Command : ctr --version
Ctr Commands:
1. List images: ctr images list
2. Pull an image: ctr images pull <image-name>
3. Remove an image: ctr images rm <image-name>
4. Create a container: ctr containers create <image-name> <container-name>
5. List containers: ctr containers list
6. Delete a container: ctr containers delete <container-name>
7. Start a task (container): ctr tasks start <container-name>
8. List running tasks: ctr tasks list
9. Kill a task: ctr tasks kill --signal SIGKILL <task-id>
10. Delete a task: ctr tasks delete <task-id>
11. To inspect metadata for a pulled image: ctr images inspect <image-name>
Nerdctl is an open-source, Docker-compatible command-line interface (CLI) built on top of containerd.
It provides a familiar Docker-like user experience while leveraging the lightweight and robust architecture of containerd.
Nerdctl is especially useful for developers transitioning from Docker to containerd or working in Kubernetes environments.
Features:
1. Encrypted container image
2. Lazy pulling
3. P2p image distribution
4. Image signing ad verifying
5. Namespace in Kubernetes ( not available in docker)
Commands :
1. Pull an image: nerdctl pull <image-name>
2. List images: nerdctl images
3. Remove an image: nerdctl rmi <image-name>
4. Run a container: nerdctl run -d --name <container-name> <image-name>
5. List running containers: nerdctl ps
6. Stop a container: nerdctl stop <container-name>
7. Remove a container: nerdctl rm <container-name>
8. Create a volume: nerdctl volume create <volume-name>
9. List volumes: nerdctl volume ls
10. Remove a volume: nerdctl volume rm <volume-name>
11. List networks: nerdctl network ls
12. Create a network: nerdctl network create <network-name>
13. Run a Docker Compose file: nerdctl compose up
14. Stop a Compose project: nerdctl compose down
CRIctl is a lightweight command-line interface (CLI) designed to interact with Kubernetes container runtimes via the Container Runtime Interface (CRI).
It is commonly used for managing and debugging containers in Kubernetes clusters.
CRIctl works with CRI-compliant runtimes like containerd, CRI-O, and others, providing a direct way to inspect and manage containers without relying on higher-level tools like kubectl
CRIctl Commands:
1. List Pods: crictl pods
12 Execute a Command in a Running Container: crictl exec <container-id> <command>
Comparing CRIctl to Other Tools
