Docs to change Container runtime

content/en/docs/tasks/administer-cluster/migrating-from-dockershim/change-runtime-containerd.md.md

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+---
+title: "Changing the container runtime from Docker Engine to containerd"
+weight: 8
+content_type: task 
+---
+This task outlines the steps needed to update your container runtime to containerd from Docker. It is applicable for cluster operators running Kubernetes 1.23 or earlier. 
+
+## Prerequisites 
+1. Install containerd. For more information see, [containerd's installation documentation](https://containerd.io/docs/getting-started/)
+
+
+2. Drain Node 
+   ```
+   # replace <node-to-drain> with the name of your node you are draining
+   kubectl drain <node-to-drain> --ignore-daemonsets
+   ```
+3. Stop the Docker daemon
+   ```
+   systemctl stop kubelet
+   systemctl stop docker
+   ```
+
+2.  Start containerd 
+
+## Migrate a Linux node {#migration-linux}
+Use the following commands to install Containerd on your system:
+
+1. Install and configure prerequisites:
+
+   ```shell
+   cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf
+   overlay
+   br_netfilter
+   EOF
+   ```
+   ```shell
+   sudo modprobe overlay
+   sudo modprobe br_netfilter
+   ```
+2. Setup required sysctl params, these persist across reboots.
+   ```shell
+      cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
+   net.bridge.bridge-nf-call-iptables  = 1
+   net.ipv4.ip_forward                 = 1
+   net.bridge.bridge-nf-call-ip6tables = 1
+   EOF
+   ```
+3. Apply sysctl params without reboot
+   ```shell
+   sudo sysctl --system
+   ```
+
+Install containerd:
+
+1. Install the `containerd.io` package from the official Docker repositories. 
+   You can find instructions for installing `containerd` at
+   [Starting Containerd](https://containerd.io/docs/getting-started/#starting-containerd).
+
+2. Configure containerd:
+
+   ```shell
+   sudo mkdir -p /etc/containerd
+   containerd config default | sudo tee /etc/containerd/config.toml
+   ```
+
+3. Restart containerd:
+
+   ```shell
+   sudo systemctl restart containerd
+   ```
+## Migrate a Windows node {#migrate-windows-powershell}
+
+Start a Powershell session, set `$Version` to the desired version (ex: `$Version=1.4.3`), 
+and then run the following commands:
+
+1. Download containerd:
+
+   ```powershell
+   curl.exe -L https://github.com/containerd/containerd/releases/download/v$Version/containerd-$Version-windows-amd64.tar.gz -o containerd-windows-amd64.tar.gz
+   tar.exe xvf .\containerd-windows-amd64.tar.gz
+   ```
+
+2. Extract and configure:
+
+   ```powershell
+   Copy-Item -Path ".\bin\" -Destination "$Env:ProgramFiles\containerd" -Recurse -Force
+   cd $Env:ProgramFiles\containerd\
+   .\containerd.exe config default | Out-File config.toml -Encoding ascii
+
+   # Review the configuration. Depending on setup you may want to adjust:
+   # - the sandbox_image (Kubernetes pause image)
+   # - cni bin_dir and conf_dir locations
+   Get-Content config.toml
+
+   # (Optional - but highly recommended) Exclude containerd from Windows Defender Scans
+   Add-MpPreference -ExclusionProcess "$Env:ProgramFiles\containerd\containerd.exe"
+   ```
+
+3. Start containerd:
+
+   ```powershell
+   .\containerd.exe --register-service
+   Start-Service containerd
+   ```
+- ## Configure the kubelet to use containerd as its container runtime {#use-containerd-as-runtime}
+
+   Edit the file `/var/lib/kubelet/kubeadm-flags.env` and add the containerd runtime to the flags. `--container-runtime=remote` and `--container-runtimeendpoint=unix:///run/containerd/containerd.sock"`
+
+   For users using kubeadm should consider the following:
+
+   Kubeadm stores the CRI socket for each host as an annotation in the Node object for that host.
+   To change it you must do the following:
+
+      - Execute `kubectl edit no <NODE-NAME>` on a machine that has the kubeadm `/etc/kubernetes/admin.conf` file.
+
+      This will start a text editor where you can edit the Node object.
+
+      To choose a text editor you can set the `KUBE_EDITOR` environment variable.
+          - Change the value of `kubeadm.alpha.kubernetes.io/cri-socket` from `/var/run/dockershim.sock`to the CRI socket path of your chose (for example `unix:///run/containerd/containerd.sock`).
+
+   Note that new CRI socket paths must be prefixed with `unix://` ideally.
+    - Save the changes in the text editor, which will update the   Node object.
+
+
+
+
+- restart kubelet
+`systemctl start kubelet`
+
+- verify pods are running 
+Run `kubectl get nodes -o wide` and containerd appears as the runtime for the node we just changed.
+
+- finally if everything goes well remove docker
+   ```
+   apt purge docker-ce docker-ce-cli
+   OR
+   yum remove docker-ce docker-ce-cli
+   ```
+
+
+