Add NCNs and UANs to External DNS

Edit the cray-externaldns-coredns ConfigMap to associate names with the Customer Access Network (CAN) IP addresses for non-compute nodes (NCNs) and User Access Nodes (UANs) in external DNS.

The cray-externaldns-coredns file contains the configuration files for external DNS’ CoreDNS instance.

Prerequisites

This procedure requires administrative privileges.

Procedure

  1. View the existing cray-externaldns-coredns ConfigMap.

    ncn-w001# kubectl -n services get configmap cray-externaldns-coredns -o jsonpath='{.data}'
map[Corefile:.:53 {
    errors
    health
    log
    ready
    kubernetes cluster.local
    k8s_external internal.shasta
    prometheus 0.0.0.0:9153
    etcd SYSTEM_DOMAIN_NAME {
        stubzones
        path /skydns
        endpoint http://cray-externaldns-etcd-client:2379
    }
}]

  2. Edit the cray-externaldns-coredns ConfigMap to add support for a static hosts file.

    ncn-w001# kubectl -n services edit configmaps cray-externaldns-coredns

    Add a “hosts” file configuration (analogous to /etc/hosts) and update the Corefile configuration so CoreDNS uses it. For example:

    data:
  Corefile: |-
    .:53 {
        errors
        health
        log
        ready
        kubernetes cluster.local
        k8s_external internal.shasta
        prometheus 0.0.0.0:9153
        hosts /etc/coredns/hosts {
           fallthrough
        }
        etcd SYSTEM_DOMAIN_NAME {
            stubzones
            path /skydns
            endpoint http://cray-externaldns-etcd-client:2379
        }
    }
  hosts: |-
    # IP FQDN short
    10.99.1.51 dn07.SYSTEM_DOMAIN_NAME dn07

  3. Restart the CoreDNS pods once the ConfigMap is updated.

    ncn-w001# kubectl -n services rollout status deployment cray-externaldns-coredns
Waiting for deployment "cray-externaldns-coredns" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "cray-externaldns-coredns" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "cray-externaldns-coredns" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "cray-externaldns-coredns" rollout to finish: 1 of 2 updated replicas are available...
deployment "cray-externaldns-coredns" successfully rolled out