Below is an example RKE template configuration file for reference.

The YAML in the RKE template uses the same customization that is used when you create an RKE cluster. However, since the YAML is within the context of a Rancher provisioned RKE cluster, the customization from the RKE docs needs to be nested under the rancher_kubernetes_engine directive.

# 
# Cluster Config
# 
docker_root_dir: /var/lib/docker
enable_cluster_alerting: false
enable_cluster_monitoring: false
enable_network_policy: false
local_cluster_auth_endpoint:
  enabled: true
# 
# Rancher Config
# 
rancher_kubernetes_engine_config: # Your RKE template config goes here.
  addon_job_timeout: 30
  authentication:
    strategy: x509
  ignore_docker_version: true
# 
# # Currently only nginx ingress provider is supported.
# # To disable ingress controller, set `provider: none`
# # To enable ingress on specific nodes, use the node_selector, eg:
#    provider: nginx
#    node_selector:
#      app: ingress
# 
  ingress:
    provider: nginx
  kubernetes_version: v1.15.3-rancher3-1
  monitoring:
    provider: metrics-server
# 
#   If you are using calico on AWS
# 
#    network:
#      plugin: calico
#      calico_network_provider:
#        cloud_provider: aws
# 
# # To specify flannel interface
# 
#    network:
#      plugin: flannel
#      flannel_network_provider:
#      iface: eth1
# 
# # To specify flannel interface for canal plugin
# 
#    network:
#      plugin: canal
#      canal_network_provider:
#        iface: eth1
# 
  network:
    options:
      flannel_backend_type: vxlan
    plugin: canal
# 
#    services:
#      kube-api:
#        service_cluster_ip_range: 10.43.0.0/16
#      kube-controller:
#        cluster_cidr: 10.42.0.0/16
#        service_cluster_ip_range: 10.43.0.0/16
#      kubelet:
#        cluster_domain: cluster.local
#        cluster_dns_server: 10.43.0.10
# 
  services:
    etcd:
      backup_config:
        enabled: true
        interval_hours: 12
        retention: 6
        safe_timestamp: false
      creation: 12h
      extra_args:
        election-timeout: 5000
        heartbeat-interval: 500
      gid: 0
      retention: 72h
      snapshot: false
      uid: 0
    kube_api:
      always_pull_images: false
      pod_security_policy: false
      service_node_port_range: 30000-32767
  ssh_agent_auth: false
windows_prefered_cluster: false