kubernetes-the-hard-way/docs/09-install-cri-workers.md

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# Installing Container Runtime on the Kubernetes Worker Nodes
In this lab you will install the Container Runtime Interface (CRI) on both worker nodes. CRI is a standard interface for the management of containers. Since v1.24 the use of dockershim has been fully deprecated and removed from the code base. [containerd replaces docker](https://kodekloud.com/blog/kubernetes-removed-docker-what-happens-now/) as the container runtime for Kubernetes, and it requires support from [CNI Plugins](https://github.com/containernetworking/plugins) to configure container networks, and [runc](https://github.com/opencontainers/runc) to actually do the job of running containers.
Reference: https://github.com/containerd/containerd/blob/main/docs/getting-started.md
### Download and Install Container Networking
The commands in this lab must be run on each worker instance: `worker-1`, and `worker-2`. Login to each controller instance using SSH Terminal.
Here we will install the container runtime `containerd` from the Ubuntu distribution, and kubectl plus the CNI tools from the Kubernetes distribution. Kubectl is required on worker-2 to initialize kubeconfig files for the worker-node auto registration.
[//]: # (host:worker-1-worker-2)
You can perform this step with [tmux](01-prerequisites.md#running-commands-in-parallel-with-tmux).
Set up the Kubernetes `apt` repository
```bash
{
KUBE_LATEST=$(curl -L -s https://dl.k8s.io/release/stable.txt | awk 'BEGIN { FS="." } { printf "%s.%s", $1, $2 }')
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://pkgs.k8s.io/core:/stable:/${KUBE_LATEST}/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/${KUBE_LATEST}/deb/ /" | sudo tee /etc/apt/sources.list.d/kubernetes.list
}
```
Install `containerd` and CNI tools, first refreshing `apt` repos to get up to date versions.
```bash
{
sudo apt update
sudo apt install -y containerd kubernetes-cni kubectl ipvsadm ipset
}
```
Set up `containerd` configuration to enable systemd Cgroups
```bash
{
sudo mkdir -p /etc/containerd
containerd config default | sed 's/SystemdCgroup = false/SystemdCgroup = true/' | sudo tee /etc/containerd/config.toml
}
```
Now restart `containerd` to read the new configuration
```bash
sudo systemctl restart containerd
```
Prev: [Bootstrapping the Kubernetes Control Plane](08-bootstrapping-kubernetes-controllers.md)</br>
Next: [Bootstrapping the Kubernetes Worker Nodes](10-bootstrapping-kubernetes-workers.md)