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Advanced Options and Configuration

This section contains advanced information describing the different ways you can run and manage RKE2.

Certificate Rotation

By default, certificates in RKE2 expire in 12 months.

If the certificates are expired or have fewer than 90 days remaining before they expire, the certificates are rotated when RKE2 is restarted.

Auto-Deploying Manifests

Any file found in /var/lib/rancher/rke2/server/manifests will automatically be deployed to Kubernetes in a manner similar to kubectl apply.

For information about deploying Helm charts using the manifests directory, refer to the section about Helm.

Configuring containerd

RKE2 will generate the config.toml for containerd in /var/lib/rancher/rke2/agent/etc/containerd/config.toml.

For advanced customization of this file you can create another file called config.toml.tmpl in the same directory and it will be used instead.

The config.toml.tmpl will be treated as a Go template file, and the config.Node structure is being passed to the template. See this template for an example of how to use the structure to customize the configuration file.

Secrets Encryption Config

RKE2 supports encrypting Secrets at rest, and will do the following automatically:

  • Generate an AES-CBC key
  • Generate an encryption config file with the generated key:
{
  "kind": "EncryptionConfiguration",
  "apiVersion": "apiserver.config.k8s.io/v1",
  "resources": [
    {
      "resources": [
        "secrets"
      ],
      "providers": [
        {
          "aescbc": {
            "keys": [
              {
                "name": "aescbckey",
                "secret": "xxxxxxxxxxxxxxxxxxx"
              }
            ]
          }
        },
        {
          "identity": {}
        }
      ]
    }
  ]
}
  • Pass the config to the Kubernetes APIServer as encryption-provider-config

Once enabled any created secret will be encrypted with this key. Note that if you disable encryption then any encrypted secrets will not be readable until you enable encryption again using the same key.

Node Labels and Taints

RKE2 agents can be configured with the options node-label and node-taint which adds a label and taint to the kubelet. The two options only add labels and/or taints at registration time, and can only be added once and not removed after that through rke2 commands.

If you want to change node labels and taints after node registration you should use kubectl. Refer to the official Kubernetes documentation for details on how to add taints and node labels.

How Agent Node Registration Works

Agent nodes are registered via a websocket connection initiated by the rke2 agent process, and the connection is maintained by a client-side load balancer running as part of the agent process.

Agents register with the server using the cluster secret portion of the join token, along with a randomly generated node-specific password, which is stored on the agent at /etc/rancher/node/password. The server will store the passwords for individual nodes as Kubernetes secrets, and any subsequent attempts must use the same password. Node password secrets are stored in the kube-system namespace with names using the template <host>.node-password.rke2. These secrets are deleted when the corresponding Kubernetes node is deleted.

Note: Prior to RKE2 v1.20.2 servers stored passwords on disk at /var/lib/rancher/rke2/server/cred/node-passwd.

If the /etc/rancher/node directory of an agent is removed, the password file should be recreated for the agent prior to startup, or the entry removed from the server or Kubernetes cluster (depending on the RKE2 version).

A unique node ID can be appended to the hostname by launching RKE2 servers or agents using the --with-node-id flag.

Starting the Server with the Installation Script

The installation script provides units for systemd, but does not enable or start the service by default.

When running with systemd, logs will be created in /var/log/syslog and viewed using journalctl -u rke2-server or journalctl -u rke2-agent.

An example of installing with the install script:

curl -sfL https://get.rke2.io | sh -
systemctl enable rke2-server
systemctl start rke2-server

Disabling Server Charts

The server charts bundled with rke2 deployed during cluster bootstrapping can be disabled and replaced with alternatives. A common use case is replacing the bundled rke2-ingress-nginx chart with an alternative.

To disable any of the bundled system charts, set the disable parameter in the config file before bootstrapping. The full list of system charts to disable is below:

  • rke2-canal
  • rke2-coredns
  • rke2-ingress-nginx
  • rke2-kube-proxy
  • rke2-metrics-server

Note that it is the cluster operator's responsibility to ensure that components are disabled or replaced with care, as the server charts play important roles in cluster operability. Refer to the architecture overview for more information on the individual system charts role within the cluster.

Installation on classified AWS regions or networks with custom AWS API endpoints

In public AWS regions, installing RKE2 with --cloud-provider-name=aws will ensure RKE2 is cloud-enabled, and capable of auto-provisioning certain cloud resources.

When installing RKE2 on classified regions (such as SC2S or C2S), there are a few additional pre-requisites to be aware of to ensure RKE2 knows how and where to securely communicate with the appropriate AWS endpoints:

  1. Ensure all the common AWS cloud-provider prerequisites are met. These are independent of regions and are always required.

  2. Ensure RKE2 knows where to send API requests for ec2 and elasticloadbalancing services by creating a cloud.conf file, the below is an example for the us-iso-east-1 (C2S) region:

# /etc/rancher/rke2/cloud.conf
[Global]
[ServiceOverride "ec2"]
  Service=ec2
  Region=us-iso-east-1
  URL=https://ec2.us-iso-east-1.c2s.ic.gov
  SigningRegion=us-iso-east-1
[ServiceOverride "elasticloadbalancing"]
  Service=elasticloadbalancing
  Region=us-iso-east-1
  URL=https://elasticloadbalancing.us-iso-east-1.c2s.ic.gov
  SigningRegion=us-iso-east-1

Alternatively, if you are using private AWS endpoints, ensure the appropriate URL is used for each of the private endpoints.

  1. Ensure the appropriate AWS CA bundle is loaded into the system's root ca trust store. This may already be done for you depending on the AMI you are using.
# on CentOS/RHEL 7/8
cp <ca.pem> /etc/pki/ca-trust/source/anchors/
update-ca-trust
  1. configure RKE2 to use the aws cloud-provider with the custom cloud.conf created in step 1:
# /etc/rancher/rke2/config.yaml
...
cloud-provider-name: aws
cloud-provider-config: "/etc/rancher/rke2/cloud.conf"
...

  1. Install RKE2 normally (most likely in an airgapped capacity)

  2. Validate successful installation by confirming the existence of AWS metadata on cluster node labels with kubectl get nodes --show-labels

Control Plane Component Resource Requests/Limits

The following options are available under the server sub-command for RKE2. The options allow for specifying CPU requests and limits for the control plane components within RKE2.

   --control-plane-resource-requests value       (components) Control Plane resource requests [$RKE2_CONTROL_PLANE_RESOURCE_REQUESTS]
   --control-plane-resource-limits value         (components) Control Plane resource limits [$RKE2_CONTROL_PLANE_RESOURCE_LIMITS]

Values are a comma-delimited list of [controlplane-component]-(cpu|memory)=[desired-value]. The possible values for controlplane-component are: 

kube-apiserver
kube-scheduler
kube-controller-manager
kube-proxy
etcd
cloud-controller-manager

Thus, an example --control-plane-resource-requests or --control-plane-resource-limits value may look like:

kube-apiserver-cpu=500m,kube-apiserver-memory=512M,kube-scheduler-cpu=250m,kube-scheduler-memory=512M,etcd-cpu=1000m

The unit values for CPU/memory are identical to Kubernetes resource units (See: Resource Limits in Kubernetes)

Extra Control Plane Component Volume Mounts

The following options are available under the server sub-command for RKE2. These options specify host-path mounting of directories from the node filesystem into the static pod component that corresponds to the prefixed name.

   --kube-apiserver-extra-mount value            (components) kube-apiserver extra volume mounts [$RKE2_KUBE_APISERVER_EXTRA_MOUNT]
   --kube-scheduler-extra-mount value            (components) kube-scheduler extra volume mounts [$RKE2_KUBE_SCHEDULER_EXTRA_MOUNT]
   --kube-controller-manager-extra-mount value   (components) kube-controller-manager extra volume mounts [$RKE2_KUBE_CONTROLLER_MANAGER_EXTRA_MOUNT]
   --kube-proxy-extra-mount value                (components) kube-proxy extra volume mounts [$RKE2_KUBE_PROXY_EXTRA_MOUNT]
   --etcd-extra-mount value                      (components) etcd extra volume mounts [$RKE2_ETCD_EXTRA_MOUNT]
   --cloud-controller-manager-extra-mount value  (components) cloud-controller-manager extra volume mounts [$RKE2_CLOUD_CONTROLLER_MANAGER_EXTRA_MOUNT]

RW Host Path Volume Mount

/source/volume/path/on/host:/destination/volume/path/in/staticpod

RO Host Path Volume Mount

In order to mount a volume as read only, append :ro to the end of the volume mount. /source/volume/path/on/host:/destination/volume/path/in/staticpod:ro

Multiple volume mounts can be specified for the same component by passing the flag values as an array in the config file.

Extra Control Plane Component Environment Variables

The following options are available under the server sub-command for RKE2. These options specify additional environment variables in standard format i.e. KEY=VALUE for the static pod component that corresponds to the prefixed name.

   --kube-apiserver-extra-env value              (components) kube-apiserver extra environment variables [$RKE2_KUBE_APISERVER_EXTRA_ENV]
   --kube-scheduler-extra-env value              (components) kube-scheduler extra environment variables [$RKE2_KUBE_SCHEDULER_EXTRA_ENV]
   --kube-controller-manager-extra-env value     (components) kube-controller-manager extra environment variables [$RKE2_KUBE_CONTROLLER_MANAGER_EXTRA_ENV]
   --kube-proxy-extra-env value                  (components) kube-proxy extra environment variables [$RKE2_KUBE_PROXY_EXTRA_ENV]
   --etcd-extra-env value                        (components) etcd extra environment variables [$RKE2_ETCD_EXTRA_ENV]
   --cloud-controller-manager-extra-env value    (components) cloud-controller-manager extra environment variables [$RKE2_CLOUD_CONTROLLER_MANAGER_EXTRA_ENV]

Multiple environment variables can be specified for the same component by passing the flag values as an array in the config file.