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Converting a connected cluster to a disconnected cluster

There might be some scenarios where you need to convert your OpenShift Container Platform cluster from a connected cluster to a disconnected cluster.

A disconnected cluster, also known as a restricted cluster, does not have an active connection to the internet. As such, you must mirror the contents of your registries and installation media. You can create this mirror registry on a host that can access both the internet and your closed network, or copy images to a device that you can move across network boundaries.

This topic describes the general process for converting an existing, connected cluster into a disconnected cluster.

About the mirror registry

You can mirror the images that are required for OpenShift Container Platform installation and subsequent product updates to a container mirror registry such as Red Hat Quay, JFrog Artifactory, Sonatype Nexus Repository, or Harbor. If you do not have access to a large-scale container registry, you can use the mirror registry for Red Hat OpenShift, a small-scale container registry included with OpenShift Container Platform subscriptions.

You can use any container registry that supports Docker v2-2, such as Red Hat Quay, the mirror registry for Red Hat OpenShift, Artifactory, Sonatype Nexus Repository, or Harbor. Regardless of your chosen registry, the procedure to mirror content from Red Hat hosted sites on the internet to an isolated image registry is the same. After you mirror the content, you configure each cluster to retrieve this content from your mirror registry.

The internal registry of the OpenShift Container Platform cluster cannot be used as the target registry because it does not support pushing without a tag, which is required during the mirroring process.

If choosing a container registry that is not the mirror registry for Red Hat OpenShift, it must be reachable by every machine in the clusters that you provision. If the registry is unreachable, installation, updating, or normal operations such as workload relocation might fail. For that reason, you must run mirror registries in a highly available way, and the mirror registries must at least match the production availability of your OpenShift Container Platform clusters.

When you populate your mirror registry with OpenShift Container Platform images, you can follow two scenarios. If you have a host that can access both the internet and your mirror registry, but not your cluster nodes, you can directly mirror the content from that machine. This process is referred to as connected mirroring. If you have no such host, you must mirror the images to a file system and then bring that host or removable media into your restricted environment. This process is referred to as disconnected mirroring.

For mirrored registries, to view the source of pulled images, you must review the Trying to access log entry in the CRI-O logs. Other methods to view the image pull source, such as using the crictl images command on a node, show the non-mirrored image name, even though the image is pulled from the mirrored location.

Red Hat does not test third party registries with OpenShift Container Platform.

Prerequisites

Preparing the cluster for mirroring

Before disconnecting your cluster, you must mirror, or copy, the images to a mirror registry that is reachable by every node in your disconnected cluster. In order to mirror the images, you must prepare your cluster by:

  • Adding the mirror registry certificates to the list of trusted CAs on your host.

  • Creating a .dockerconfigjson file that contains your image pull secret, which is from the cloud.openshift.com token.

Procedure

  1. Configuring credentials that allow image mirroring:

    1. Add the CA certificate for the mirror registry, in the simple PEM or DER file formats, to the list of trusted CAs. For example:

      $ cp </path/to/cert.crt> /usr/share/pki/ca-trust-source/anchors/
      where
      </path/to/cert.crt>

      Specifies the path to the certificate on your local file system.

    2. Update the CA trust. For example, in Linux:

      $ update-ca-trust

    3. Extract the .dockerconfigjson file from the global pull secret:

      $ oc extract secret/pull-secret -n openshift-config --confirm --to=.
      Example output
      .dockerconfigjson

    4. Edit the .dockerconfigjson file to add your mirror registry and authentication credentials and save it as a new file:

      {"auths":{"<local_registry>": {"auth": "<credentials>","email": "you@example.com"}}},"<registry>:<port>/<namespace>/":{"auth":"<token>"}}}

      where:

      <local_registry>

      Specifies the registry domain name, and optionally the port, that your mirror registry uses to serve content.

      auth

      Specifies the base64-encoded user name and password for your mirror registry.

      <registry>:<port>/<namespace>

      Specifies the mirror registry details.

      <token>

      Specifies the base64-encoded username:password for your mirror registry.

      For example:

      $ {"auths":{"cloud.openshift.com":{"auth":"b3BlbnNoaWZ0Y3UjhGOVZPT0lOMEFaUjdPUzRGTA==","email":"user@example.com"},
"quay.io":{"auth":"b3BlbnNoaWZ0LXJlbGVhc2UtZGOVZPT0lOMEFaUGSTd4VGVGVUjdPUzRGTA==","email":"user@example.com"},
"registry.connect.redhat.com"{"auth":"NTE3MTMwNDB8dWhjLTFEZlN3VHkxOSTd4VGVGVU1MdTpleUpoYkdjaUailA==","email":"user@example.com"},
"registry.redhat.io":{"auth":"NTE3MTMwNDB8dWhjLTFEZlN3VH3BGSTd4VGVGVU1MdTpleUpoYkdjaU9fZw==","email":"user@example.com"},
"registry.svc.ci.openshift.org":{"auth":"dXNlcjpyWjAwWVFjSEJiT2RKVW1pSmg4dW92dGp1SXRxQ3RGN1pwajJhN1ZXeTRV"},"my-registry:5000/my-namespace/":{"auth":"dXNlcm5hbWU6cGFzc3dvcmQ="}}}

Mirroring the images

After the cluster is properly configured, you can mirror the images from your external repositories to the mirror repository.

Procedure

  1. Mirror the Operator Lifecycle Manager (OLM) images:

    $ oc adm catalog mirror registry.redhat.io/redhat/redhat-operator-index:v{product-version} <mirror_registry>:<port>/olm -a <reg_creds>

    where:

    product-version

    Specifies the tag that corresponds to the version of OpenShift Container Platform to install, such as 4.8.

    mirror_registry

    Specifies the fully qualified domain name (FQDN) for the target registry and namespace to mirror the Operator content to, where <namespace> is any existing namespace on the registry.

    reg_creds

    Specifies the location of your modified .dockerconfigjson file.

    For example:

    $ oc adm catalog mirror registry.redhat.io/redhat/redhat-operator-index:v4.8 mirror.registry.com:443/olm -a ./.dockerconfigjson  --index-filter-by-os='.*'

  2. Mirror the content for any other Red Hat-provided Operator:

    $ oc adm catalog mirror <index_image> <mirror_registry>:<port>/<namespace> -a <reg_creds>

    where:

    index_image

    Specifies the index image for the catalog you want to mirror. For example, this might be a pruned index image that you created previously, or one of the source index images for the default catalogs, such as {index-image-pullspec}.

    mirror_registry

    Specifies the FQDN for the target registry and namespace to mirror the Operator content to, where <namespace> is any existing namespace on the registry.

    reg_creds

    Optional: Specifies the location of your registry credentials file, if required.

    For example:

    $ oc adm catalog mirror registry.redhat.io/redhat/community-operator-index:v4.8 mirror.registry.com:443/olm -a ./.dockerconfigjson  --index-filter-by-os='.*'

  3. Mirror the OpenShift Container Platform image repository:

    $ oc adm release mirror -a .dockerconfigjson --from=quay.io/openshift-release-dev/ocp-release:v<product-version>-<architecture> --to=<local_registry>/<local_repository> --to-release-image=<local_registry>/<local_repository>:v<product-version>-<architecture>

    where:

    product-version

    Specifies the tag that corresponds to the version of OpenShift Container Platform to install, such as 4.8.15-x86_64.

    architecture

    Specifies the type of architecture for your server, such as x86_64.

    local_registry

    Specifies the registry domain name for your mirror repository.

    local_repository

    Specifies the name of the repository to create in your registry, such as ocp4/openshift4.

    For example:

    $ oc adm release mirror -a .dockerconfigjson --from=quay.io/openshift-release-dev/ocp-release:4.8.15-x86_64 --to=mirror.registry.com:443/ocp/release --to-release-image=mirror.registry.com:443/ocp/release:4.8.15-x86_64
    Example output
    info: Mirroring 109 images to mirror.registry.com/ocp/release ...
mirror.registry.com:443/
  ocp/release
	manifests:
  	sha256:086224cadce475029065a0efc5244923f43fb9bb3bb47637e0aaf1f32b9cad47 -> 4.8.15-x86_64-thanos
  	sha256:0a214f12737cb1cfbec473cc301aa2c289d4837224c9603e99d1e90fc00328db -> 4.8.15-x86_64-kuryr-controller
  	sha256:0cf5fd36ac4b95f9de506623b902118a90ff17a07b663aad5d57c425ca44038c -> 4.8.15-x86_64-pod
  	sha256:0d1c356c26d6e5945a488ab2b050b75a8b838fc948a75c0fa13a9084974680cb -> 4.8.15-x86_64-kube-client-agent

…..
sha256:66e37d2532607e6c91eedf23b9600b4db904ce68e92b43c43d5b417ca6c8e63c mirror.registry.com:443/ocp/release:4.5.41-multus-admission-controller
sha256:d36efdbf8d5b2cbc4dcdbd64297107d88a31ef6b0ec4a39695915c10db4973f1 mirror.registry.com:443/ocp/release:4.5.41-cluster-kube-scheduler-operator
sha256:bd1baa5c8239b23ecdf76819ddb63cd1cd6091119fecdbf1a0db1fb3760321a2 mirror.registry.com:443/ocp/release:4.5.41-aws-machine-controllers
info: Mirroring completed in 2.02s (0B/s)

Success
Update image:  mirror.registry.com:443/ocp/release:4.5.41-x86_64
Mirror prefix: mirror.registry.com:443/ocp/release

  4. Mirror any other registries, as needed:

    $ oc image mirror <online_registry>/my/image:latest <mirror_registry>
Additional information

Configuring the cluster for the mirror registry

After creating and mirroring the images to the mirror registry, you must modify your cluster so that pods can pull images from the mirror registry.

You must:

  • Add the mirror registry credentials to the global pull secret.

  • Add the mirror registry server certificate to the cluster.

  • Create an ImageContentSourcePolicy custom resource (ICSP), which associates the mirror registry with the source registry.

    1. Add mirror registry credential to the cluster global pull-secret:

      $ oc set data secret/pull-secret -n openshift-config --from-file=.dockerconfigjson=<pull_secret_location> (1)
      1 Provide the path to the new pull secret file.

      For example:

      $ oc set data secret/pull-secret -n openshift-config --from-file=.dockerconfigjson=.mirrorsecretconfigjson

    2. Add the CA-signed mirror registry server certificate to the nodes in the cluster:

      1. Create a config map that includes the server certificate for the mirror registry

        $ oc create configmap <config_map_name> --from-file=<mirror_address_host>..<port>=$path/ca.crt -n openshift-config

        For example:

        S oc create configmap registry-config --from-file=mirror.registry.com..443=/root/certs/ca-chain.cert.pem -n openshift-config

      2. Use the config map to update the image.config.openshift.io/cluster custom resource (CR). OpenShift Container Platform applies the changes to this CR to all nodes in the cluster:

        $ oc patch image.config.openshift.io/cluster --patch '{"spec":{"additionalTrustedCA":{"name":"<config_map_name>"}}}' --type=merge

        For example:

        $ oc patch image.config.openshift.io/cluster --patch '{"spec":{"additionalTrustedCA":{"name":"registry-config"}}}' --type=merge

    3. Create an ICSP to redirect container pull requests from the online registries to the mirror registry:

      1. Create the ImageContentSourcePolicy custom resource:

        apiVersion: operator.openshift.io/v1alpha1
kind: ImageContentSourcePolicy
metadata:
  name: mirror-ocp
spec:
  repositoryDigestMirrors:
  - mirrors:
    - mirror.registry.com:443/ocp/release (1)
    source: quay.io/openshift-release-dev/ocp-release (2)
  - mirrors:
    - mirror.registry.com:443/ocp/release
    source: quay.io/openshift-release-dev/ocp-v4.0-art-dev
        1 Specifies the name of the mirror image registry and repository.
        2 Specifies the online registry and repository containing the content that is mirrored.

      2. Create the ICSP object:

        $ oc create -f registryrepomirror.yaml
        Example output
        imagecontentsourcepolicy.operator.openshift.io/mirror-ocp created

        OpenShift Container Platform applies the changes to this CR to all nodes in the cluster.

    4. Verify that the credentials, CA, and ICSP for mirror registry were added:

      1. Log into a node:

        $ oc debug node/<node_name>

      2. Set /host as the root directory within the debug shell:

        sh-4.4# chroot /host

      3. Check the config.json file for the credentials:

        sh-4.4# cat /var/lib/kubelet/config.json
        Example output
        {"auths":{"brew.registry.redhat.io":{"xx=="},"brewregistry.stage.redhat.io":{"auth":"xxx=="},"mirror.registry.com:443":{"auth":"xx="}}} (1)
        1 Ensure that the mirror registry and credentials are present.

      4. Change to the certs.d directory

        sh-4.4#