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How Do I Select a Container Runtime?

Introduction to Container Runtime

Container runtime, one of the most important components of Kubernetes, manages the lifecycle of images and containers. kubelet interacts with a container runtime through the Container Runtime Interface (CRI) to manage images and containers.

CCE allows you to select containerd or Docker as the container runtime.

  • containerd has a shorter tracing and fewer components is fewer, which is more stable and occupies fewer node resources. It is recommended that you select containerd as your container runtime.
  • Docker is suitable in the following scenarios:
    • Docker-in-Docker needs to be used.
    • Commands such as docker build/push/save/load need to be run on the CCE node.
    • Docker APIs need to be called.
    • Docker Compose or Docker Swarm needs to be used.

Common Commands of containerd and Docker

containerd does not support Docker APIs and Docker CLI, but you can run crictl commands to implement similar functions.

Table 1 Image-related commands

No.

Docker Command

containerd Command

Remarks

1

docker images [Option] [Image name[:Tag]]

crictl images [Option] [Image name[:Tag]]

List local images.

2

docker pull [Option] Image name[:Tag|@DIGEST]

crictl pull [Option] Image name[:Tag|@DIGEST]

Pull images.

3

docker push

None

Push an image.

4

docker rmi [Option] Image...

crictl rmi [Option] Image ID...

Delete a local image.

5

docker inspect Image ID

crictl inspect Image ID

Check a container.
Table 2 Container-related commands

No.

Docker Command

containerd Command

Remarks

1

docker ps [Option]

crictl ps [Option]

List containers.

2

docker create [Option]

crictl create [Option]

Create a container.

3

docker start [Option] Container ID...

crictl start [Option] Container ID...

Start a container.

4

docker stop [Option] Container ID...

crictl stop [Option] Container ID...

Stop a container.

5

docker rm [Option] Container ID...

crictl rm [Option] Container ID...

Delete a container.

6

docker attach [Option] Container ID

crictl attach [Option] Container ID

Connect to a container.

7

docker exec [Option] Container ID Startup command [Parameter...]

crictl exec [Option] Container ID Startup command [Parameter...]

Access the container.

8

docker inspect [Option] Container name|ID...

crictl inspect [Option] Container ID...

Query container details.

9

docker logs [Option] Container ID

crictl logs [Option] Container ID

View container logs.

10

docker stats [Option] Container ID...

crictl stats [Option] Container ID

Check the resource usage of the container.

11

docker update [Option] Container ID...

crictl update [Option] Container ID...

Update container resource limits.
Table 3 Pod-related commands

No.

Docker Command

containerd Command

Remarks

1

None

crictl pods [Option]

List pods.

2

None

crictl inspectp [Option] Pod ID...

View pod details.

3

None

crictl start [Option] Pod ID...

Start a pod.

4

None

crictl runp [Option] Pod ID...

Run a pod.

5

None

crictl stopp [Option] Pod ID...

Stop a pod.

6

None

crictl rmp [Option] Pod ID...

Delete a pod.

Containers created and started by containerd are immediately deleted by kubelet. containerd does not support suspending, resuming, restarting, renaming, and waiting for containers, nor Docker image build, import, export, comparison, push, search, and labeling. containerd does not support file copy. You can log in to the image repository by modifying the configuration file of containerd.

Differences in Tracing

  • When Docker is used as the container runtime, the tracing is as follows:

    kubelet --> docker shim (in the kubelet process) --> dockerd --> containerd

  • When containerd is used as the container runtime, the tracing is as follows:

    kubelet --> cri plugin (in the containerd process) --> containerd

Although Docker has added functions such as swarm cluster, docker build, and Docker APIs, it also introduces bugs. Compared with containerd, Docker has one more layer of calling.

Parent topic: Container