Configuring a private cluster

By default, OKD is provisioned using publicly-accessible DNS and endpoints. You can set the DNS, Ingress Controller, and API server to private after you deploy your cluster.

If you install OKD on installer-provisioned infrastructure, the installation program creates records in a pre-existing public zone and, where possible, creates a private zone for the cluster’s own DNS resolution. In both the public zone and the private zone, the installation program or cluster creates DNS entries for , for the Ingress object, and api, for the API server.

The *.apps records in the public and private zone are identical, so when you delete the public zone, the private zone seamlessly provides all DNS resolution for the cluster.

Because the default Ingress object is created as public, the load balancer is internet-facing and in the public subnets. You can replace the default Ingress Controller with an internal one.

By default, the installation program creates appropriate network load balancers for the API server to use for both internal and external traffic.

On Amazon Web Services (AWS), separate public and private load balancers are created. The load balancers are identical except that an additional port is available on the internal one for use within the cluster. Although the installation program automatically creates or destroys the load balancer based on API server requirements, the cluster does not manage or maintain them. As long as you preserve the cluster’s access to the API server, you can manually modify or move the load balancers. For the public load balancer, port 6443 is open and the health check is configured for HTTPS against the /readyz path.

On Google Cloud Platform, a single load balancer is created to manage both internal and external API traffic, so you do not need to modify the load balancer.

On Microsoft Azure, both public and private load balancers are created. However, because of limitations in current implementation, you just retain both load balancers in a private cluster.

After you deploy a cluster, you can modify its DNS to use only a private zone.

Procedure

1. Review the DNS custom resource for your cluster:

   Example output

   apiVersion: config.openshift.io/v1
   kind: DNS
   metadata:
     creationTimestamp: "2019-10-25T18:27:09Z"
     generation: 2
     name: cluster
     resourceVersion: "37966"
     selfLink: /apis/config.openshift.io/v1/dnses/cluster
     uid: 0e714746-f755-11f9-9cb1-02ff55d8f976
   spec:
     baseDomain: <base_domain>
     privateZone:
       tags:
         Name: <infrastructure_id>-int
         kubernetes.io/cluster/<infrastructure_id>: owned
     publicZone:
       id: Z2XXXXXXXXXXA4
   status: {}

   Note that the spec section contains both a private and a public zone.

2. $ oc patch dnses.config.openshift.io/cluster --type=merge --patch='{"spec": {"publicZone": null}}'
   dns.config.openshift.io/cluster patched

   Because the Ingress Controller consults the definition when it creates Ingress objects, when you create or modify Ingress objects, only private records are created.

After you deploy a cluster, you can modify its Ingress Controller to use only a private zone.

Procedure

1. Modify the default Ingress Controller to use only an internal endpoint:

   $ oc replace --force --wait --filename - <<EOF
   apiVersion: operator.openshift.io/v1
   kind: IngressController
   metadata:
     namespace: openshift-ingress-operator
     name: default
   spec:
     endpointPublishingStrategy:
       type: LoadBalancerService
         scope: Internal
   EOF

   Example output

   The public DNS entry is removed, and the private zone entry is updated.

After you deploy a cluster to Amazon Web Services (AWS) or Microsoft Azure, you can reconfigure the API server to use only the private zone.

Prerequisites

• Have access to the web console as a user with admin privileges.

1. In the web portal or console for AWS or Azure, take the following actions:

   1. Locate and delete appropriate load balancer component.

      • For AWS, delete the external load balancer. The API DNS entry in the private zone already points to the internal load balancer, which uses an identical configuration, so you do not need to modify the internal load balancer.

      • For Azure, delete the api-internal rule for the load balancer.

   2. Delete the api.$clustername.$yourdomain DNS entry in the public zone.

2. Remove the external load balancers:

   1. From your terminal, list the cluster machines:

      $ oc get machine -n openshift-machine-api

      Example output

      NAME                            STATE     TYPE        REGION      ZONE         AGE
      lk4pj-master-0                  running   m4.xlarge   us-east-1   us-east-1a   17m
      lk4pj-master-1                  running   m4.xlarge   us-east-1   us-east-1b   17m
      lk4pj-master-2                  running   m4.xlarge   us-east-1   us-east-1a   17m
      lk4pj-worker-us-east-1a-5fzfj   running   m4.xlarge   us-east-1   us-east-1a   15m
      lk4pj-worker-us-east-1a-vbghs   running   m4.xlarge   us-east-1   us-east-1a   15m
      lk4pj-worker-us-east-1b-zgpzg   running   m4.xlarge   us-east-1   us-east-1b   15m

      You modify the control plane machines, which contain master in the name, in the following step.

   2. Remove the external load balancer from each control plane machine.

      1. Edit a control plane Machine object to remove the reference to the external load balancer:

      2. Remove the lines that describe the external load balancer, which are marked in the following example, and save and exit the object specification:

         ...
         spec:
           providerSpec:
             value:
             ...
               loadBalancers:
               - name: lk4pj-ext (1)
                 type: network (1)
               - name: lk4pj-int
                 type: network