Removing Kubernetes Components from Nodes

This section describes how to disconnect a node from a Rancher-launched Kubernetes cluster and remove all of the Kubernetes components from the node. This process allows you to use the node for other purposes.

When you use Rancher to install Kubernetes on new nodes in an infrastructure provider, resources (containers/virtual network interfaces) and configuration items (certificates/configuration files) are created.

When removing nodes from your Rancher launched Kubernetes cluster (provided that they are in Active state), those resources are automatically cleaned, and the only action needed is to restart the node. When a node has become unreachable and the automatic cleanup process cannot be used, we describe the steps that need to be executed before the node can be added to a cluster again.

What Gets Removed?

When cleaning nodes provisioned using Rancher, the following components are deleted based on the type of cluster node you’re removing.

Removing a Node from a Cluster by Rancher UI

When the node is in Active state, removing the node from a cluster will trigger a process to clean up the node. Please restart the node after the automatic cleanup process is done to make sure any non-persistent data is properly removed.

To restart a node:

# using reboot
$ sudo reboot
# using shutdown
$ sudo shutdown -r now

Removing Rancher Components from a Cluster Manually

When a node is unreachable and removed from the cluster, the automatic cleaning process can’t be triggered because the node is unreachable. Please follow the steps below to manually remove the Rancher components.

danger

The commands listed below will remove data from the node. Make sure you have created a backup of files you want to keep before executing any of the commands as data will be lost.

Removing Rancher Components from Registered Clusters

For registered clusters, the process for removing Rancher is a little different. You have the option of simply deleting the cluster in the Rancher UI, or your can run a script that removes Rancher components from the nodes. Both options make the same deletions.

After the registered cluster is detached from Rancher, the cluster’s workloads will be unaffected and you can access the cluster using the same methods that you did before the cluster was registered into Rancher.

• By UI / API
• By Script

danger

This process will remove data from your cluster. Make sure you have created a backup of files you want to keep before executing the command, as data will be lost.

After you initiate the removal of a registered cluster using the Rancher UI (or API), the following events occur.

1. Rancher creates a serviceAccount that it uses to remove the Rancher components from the cluster. This account is assigned the clusterRole and clusterRoleBinding permissions, which are required to remove the Rancher components.

2. Using the serviceAccount, Rancher schedules and runs a job that cleans the Rancher components off of the cluster. This job also references the serviceAccount and its roles as dependencies, so the job deletes them before its completion.

3. Rancher is removed from the cluster. However, the cluster persists, running the native version of Kubernetes.

Result: All components listed for registered clusters in What Gets Removed? are deleted.

Rather than cleaning registered cluster nodes using the Rancher UI, you can run a script instead.

Prerequisite:

Install kubectl.

1. Open a web browser, navigate to GitHub, and download user-cluster.sh.

2. Make the script executable by running the following command from the same directory as user-cluster.sh:

   chmod +x user-cluster.sh

3. Air Gap Environments Only: Open user-cluster.sh and replace yaml_url with the URL in user-cluster.yml.

   If you don’t have an air gap environment, skip this step.

4. From the same directory, run the script and provide the rancher/rancher-agent image version which should be equal to the version of Rancher used to manage the cluster. (<RANCHER_VERSION>):

   tip

   Add the -dry-run flag to preview the script’s outcome without making changes.

   ./user-cluster.sh rancher/rancher-agent:<RANCHER_VERSION>

Result: The script runs. All components listed for registered clusters in What Gets Removed? are deleted.

Cleaning up Nodes

• RKE1
• RKE2
• K3s

Windows Nodes

To clean up a Windows node, you can run a cleanup script located in c:\etc\rancher. The script deletes Kubernetes generated resources and the execution binary. It also drops the firewall rules and network settings.

To run the script, you can use this command in the PowerShell:

pushd c:\etc\rancher
.\cleanup.ps1
popd

Result: The node is reset and can be re-added to a Kubernetes cluster.

Docker Containers, Images, and Volumes

Based on what role you assigned to the node, there are Kubernetes components in containers, containers belonging to overlay networking, DNS, ingress controller and Rancher agent. (and pods you created that have been scheduled to this node)

To clean all Docker containers, images and volumes:

docker rm -f $(docker ps -qa)
docker rmi -f $(docker images -q)
docker volume rm $(docker volume ls -q)

Mounts

Kubernetes components and secrets leave behind mounts on the system that need to be unmounted.

To unmount all mounts:

for mount in $(mount | grep tmpfs | grep '/var/lib/kubelet' | awk '{ print $3 }') /var/lib/kubelet /var/lib/rancher; do umount $mount; done

There are two components that need to be removed on nodes of an RKE2 cluster that was provisioned through Rancher:

• The rancher-system-agent, which connects to Rancher and installs and manages RKE2
• RKE2 itself

Removing rancher-system-agent

To remove the rancher-system-agent, run the system-agent-uninstall.sh script:

curl https://raw.githubusercontent.com/rancher/system-agent/main/system-agent-uninstall.sh | sudo sh

Removing RKE2

To remove the RKE2 installation, run the rke2-uninstall script that is already present on the node:

sudo rke2-uninstall.sh

There are two components that need to be removed on nodes of a K3s cluster that was provisioned through Rancher:

• The rancher-system-agent, which connects to Rancher and installs and manages K3s
• K3s itself

Removing rancher-system-agent

To remove the rancher-system-agent, run the system-agent-uninstall.sh script:

curl https://raw.githubusercontent.com/rancher/system-agent/main/system-agent-uninstall.sh | sudo sh

Removing K3s

To remove the K3s installation, run the k3s-uninstall script that is already present on the node:

sudo k3s-uninstall.sh

Directories and Files

The following directories are used when adding a node to a cluster, and should be removed. You can remove a directory using rm -rf /directory_name.

note

Depending on the role you assigned to the node, some of the directories will or won’t be present on the node.

To clean the directories:

rm -rf /etc/ceph \
       /etc/cni \
       /etc/kubernetes \
       /etc/rancher \
       /opt/cni \
       /opt/rke \
       /run/secrets/kubernetes.io \
       /run/calico \
       /run/flannel \
       /var/lib/calico \
       /var/lib/etcd \
       /var/lib/cni \
       /var/lib/kubelet \
       /var/lib/rancher\
       /var/log/containers \
       /var/log/kube-audit \
       /var/log/pods \
       /var/run/calico

Network Interfaces and Iptables

The remaining two components that are changed/configured are (virtual) network interfaces and iptables rules. Both are non-persistent to the node, meaning that they will be cleared after a restart of the node. To remove these components, a restart is recommended.

To restart a node:

# using reboot
$ sudo reboot
# using shutdown
$ sudo shutdown -r now

If you want to know more on (virtual) network interfaces or iptables rules, please see the specific subjects below.

Network Interfaces

note

Depending on the network provider configured for the cluster the node was part of, some of the interfaces will or won’t be present on the node.

To list all interfaces:

# Using ip
ip address show
# Using ifconfig
ifconfig -a

To remove an interface:

ip link delete interface_name

Iptables

note

Depending on the network provider configured for the cluster the node was part of, some of the chains will or won’t be present on the node.

Iptables rules are used to route traffic from and to containers. The created rules are not persistent, so restarting the node will restore iptables to its original state.

To list all iptables rules:

iptables -L -t nat
iptables -L -t mangle
iptables -L