DNS management

To install CoreDNS components for DNS management, use the kube-dns module.

To enable kube-dns with default settings, use the following ModuleConfig resource:

d8 k apply -f - <<EOF
apiVersion: deckhouse.io/v1alpha1
kind: ModuleConfig
metadata:
  name: kube-dns
spec:
  enabled: true
EOF

For detailed description of kube-dns settings, refer to the corresponding article.

DNS configuration example

Example of the kube-dns module configuration using the ModuleConfig resource:

d8 k apply -f - <<EOF
apiVersion: deckhouse.io/v1alpha1
kind: ModuleConfig
metadata:
  name: kube-dns
spec:
  version: 1
  enabled: true
  settings:
    # A list of IP addresses for recursive DNS servers that CoreDNS uses to resolve external domains
    # By default, it uses the list from /etc/resolv.conf
    upstreamNameservers:
      - 8.8.8.8
      - 8.8.4.4
    # A static list of hosts formatted similarly to /etc/hosts
    hosts:
      - domain: one.example.com
        ip: 192.168.0.1
      - domain: two.another.example.com
        ip: 10.10.0.128
    # A list of additional zones managed by CoreDNS
    stubZones:
      - zone: consul.local
        upstreamNameservers:
          - 10.150.0.1
    # A list of alternative cluster domains resolved along with global.discovery.clusterDomain
    clusterDomainAliases:
      - foo.bar
      - baz.qux
EOF

For detailed description of kube-dns settings, refer to the corresponding article.

Replace a cluster domain

To replace a cluster domain with minimal downtime, follow these steps:

1. Edit the settings of the control-plane manager module responsible for Deckhouse configuration.

   Make changes using the following template:

   apiVersion: deckhouse.io/v1alpha1
   kind: ModuleConfig
   metadata:
     name: control-plane-manager
   spec:
     version: 1
     enabled: true
     settings:
       apiserver:
         # A list of SANs certificate options for generating the API server certificate
         certSANs:
          - kubernetes.default.svc.<old clusterDomain>
          - kubernetes.default.svc.<new clusterDomain>
         serviceAccount:
           # A list of API audiences to include when creating ServiceAccount tokens
           additionalAPIAudiences:
           - https://kubernetes.default.svc.<old clusterDomain>
           - https://kubernetes.default.svc.<new clusterDomain>
           # A list of additional ServiceAccount API token issuers to add as they are created
           additionalAPIIssuers:
           - https://kubernetes.default.svc.<old clusterDomain>
           - https://kubernetes.default.svc.<new clusterDomain>
   

2. Add a list of alternative cluster domains to the kube-dns module configuration:

   apiVersion: deckhouse.io/v1alpha1
   kind: ModuleConfig
   metadata:
     name: kube-dns
   spec:
     version: 1
     enabled: true
     settings:
       clusterDomainAliases:
         - <old clusterDomain>
         - <new clusterDomain>
   

3. Wait for kube-apiserver to restart.
4. Replace clusterDomain with a new domain in dhctl config edit cluster-configuration.