As one of the most important components of Kubernetes (K8s), a container runtime manages the lifecycle of images and containers. Kubelet interacts with the container runtime through the
Container Runtime Interface (CRI) to manage images and containers.
You can choose Containerd and Docker as container runtime components:
Modifications on the runtime component and version only take effect for added nodes that are not assigned to any node pool. The existing nodes are not affected.
Containerd does not support docker API or docker CLI. However, you can get similar features with the
|Display the local image list||docker images||crictl images|
|Download an image||docker pull||crictl pull|
|Upload an image||docker push||None|
|Delete a local image||docker rmi||crictl rmi|
|View image details||docker inspect IMAGE-ID||crictl inspect IMAGE-ID|
|Display the container list||docker ps||crictl ps|
|Create a container||docker create||crictl create|
|Start a container||docker start||crictl start|
|Stop a container||docker stop||crictl stop|
|Delete a container||docker rm||crictl rm|
|View container details||docker inspect||crictl inspect|
|attach||docker attach||crictl attach|
|exec||docker exec||crictl exec|
|logs||docker logs||crictl logs|
|stats||docker stats||crictl stats|
|Display the Pod list||None||crictl pods|
|View Pod details||None||crictl inspectp|
|Run a Pod||None||crictl runp|
|Stop a Pod||None||crictl stopp|
kubelet --> docker shim (in the kubelet process) --> dockerd --> containerd
kubelet --> cri plugin (in the containerd process) --> containerd
Although Docker offers more features such as swarm cluster, docker build, and docker API, it may also introduce some bugs and requires one more calling step than containerd.
Commands such as
kubectl logsrequire the establishment of a stream forwarding tunnel between the apiserver and the container runtime.
The docker API itself provides a stream service, and the docker-shim inside the Kubelet forwards streams through the docker API.
The stream service of Containerd needs to be configured separately:
[plugins.cri] stream_server_address = "127.0.0.1" stream_server_port = "0" enable_tls_streaming = false
The stream service of Containerd has different configurations for different versions of K8s.
If Docker serves as the K8s container runtime, it saves container logs to a directory such as
If Containerd serves as the K8s container runtime, Kubelet saves container logs to the
Specify in the Docker configuration files:
|Save container logs to the data disk||Mount the data disk to `data-root` (
||Create a soft link
Selecting "Store containers and images in the data disk" in TKE will automatically create the soft link
|Component responsible for calling CNI||docker-shim inside Kubelet||Containerd's built-in cri-plugin (in containerd v1.1 or later)|
|How to configure CNI||Kubelet parameters
||Containerd configuration file (toml):