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Chapter 9. Image configuration resources

Use the following procedure to configure image registries.

9.1. Image controller configuration parameters

The image.config.openshift.io/cluster resource holds cluster-wide information about how to handle images. The canonical, and only valid name is cluster. Its spec offers the following configuration parameters.

Note

Parameters such as DisableScheduledImport, MaxImagesBulkImportedPerRepository, MaxScheduledImportsPerMinute, ScheduledImageImportMinimumIntervalSeconds, InternalRegistryHostname are not configurable.

ParameterDescription

allowedRegistriesForImport

Limits the container image registries from which normal users can import images. Set this list to the registries that you trust to contain valid images, and that you want applications to be able to import from. Users with permission to create images or ImageStreamMappings from the API are not affected by this policy. Typically only cluster administrators have the appropriate permissions.

Every element of this list contains a location of the registry specified by the registry domain name.

domainName: Specifies a domain name for the registry. If the registry uses a non-standard 80 or 443 port, the port should be included in the domain name as well.

insecure: Insecure indicates whether the registry is secure or insecure. By default, if not otherwise specified, the registry is assumed to be secure.

additionalTrustedCA

A reference to a config map containing additional CAs that should be trusted during image stream import, pod image pull, openshift-image-registry pullthrough, and builds.

The namespace for this config map is openshift-config. The format of the config map is to use the registry hostname as the key, and the PEM-encoded certificate as the value, for each additional registry CA to trust.

externalRegistryHostnames

Provides the hostnames for the default external image registry. The external hostname should be set only when the image registry is exposed externally. The first value is used in publicDockerImageRepository field in image streams. The value must be in hostname[:port] format.

registrySources

Contains configuration that determines how the container runtime should treat individual registries when accessing images for builds and pods. For instance, whether or not to allow insecure access. It does not contain configuration for the internal cluster registry.

insecureRegistries: Registries which do not have a valid TLS certificate or only support HTTP connections. To specify all subdomains, add the asterisk (*) wildcard character as a prefix to the domain name. For example, *.example.com. You can specify an individual repository within a registry. For example: reg1.io/myrepo/myapp:latest.

blockedRegistries: Registries for which image pull and push actions are denied. To specify all subdomains, add the asterisk (*) wildcard character as a prefix to the domain name. For example, *.example.com. You can specify an individual repository within a registry. For example: reg1.io/myrepo/myapp:latest. All other registries are allowed.

allowedRegistries: Registries for which image pull and push actions are allowed. To specify all subdomains, add the asterisk (*) wildcard character as a prefix to the domain name. For example, *.example.com. You can specify an individual repository within a registry. For example: reg1.io/myrepo/myapp:latest. All other registries are blocked.

containerRuntimeSearchRegistries: Registries for which image pull and push actions are allowed using image short names. All other registries are blocked.

Either blockedRegistries or allowedRegistries can be set, but not both.

Warning

When the allowedRegistries parameter is defined, all registries, including registry.redhat.io and quay.io registries and the default OpenShift image registry, are blocked unless explicitly listed. When using the parameter, to prevent pod failure, add all registries including the registry.redhat.io and quay.io registries and the internalRegistryHostname to the allowedRegistries list, as they are required by payload images within your environment. For disconnected clusters, mirror registries should also be added.

The status field of the image.config.openshift.io/cluster resource holds observed values from the cluster.

ParameterDescription

internalRegistryHostname

Set by the Image Registry Operator, which controls the internalRegistryHostname. It sets the hostname for the default OpenShift image registry. The value must be in hostname[:port] format. For backward compatibility, you can still use the OPENSHIFT_DEFAULT_REGISTRY environment variable, but this setting overrides the environment variable.

externalRegistryHostnames

Set by the Image Registry Operator, provides the external hostnames for the image registry when it is exposed externally. The first value is used in publicDockerImageRepository field in image streams. The values must be in hostname[:port] format.

9.2. Configuring image registry settings

You can configure image registry settings by editing the image.config.openshift.io/cluster custom resource (CR). When changes to the registry are applied to the image.config.openshift.io/cluster CR, the Machine Config Operator (MCO) performs the following sequential actions:

  1. Cordons the node
  2. Applies changes by restarting CRI-O

  3. Uncordons the node

    Note

    The MCO does not restart nodes when it detects changes.

Procedure

  1. Edit the image.config.openshift.io/cluster custom resource: 

    $ oc edit image.config.openshift.io/cluster

    The following is an example image.config.openshift.io/cluster CR: 

    apiVersion: config.openshift.io/v1
kind: Image 1
metadata:
  annotations:
    release.openshift.io/create-only: "true"
  creationTimestamp: "2019-05-17T13:44:26Z"
  generation: 1
  name: cluster
  resourceVersion: "8302"
  selfLink: /apis/config.openshift.io/v1/images/cluster
  uid: e34555da-78a9-11e9-b92b-06d6c7da38dc
spec:
  allowedRegistriesForImport: 2
    - domainName: quay.io
      insecure: false
  additionalTrustedCA: 3
    name: myconfigmap
  registrySources: 4
    allowedRegistries:
    - example.com
    - quay.io
    - registry.redhat.io
    - image-registry.openshift-image-registry.svc:5000
    - reg1.io/myrepo/myapp:latest
    insecureRegistries:
    - insecure.com
status:
  internalRegistryHostname: image-registry.openshift-image-registry.svc:5000
    1
    Image: Holds cluster-wide information about how to handle images. The canonical, and only valid name is cluster.
    2
    allowedRegistriesForImport: Limits the container image registries from which normal users may import images. Set this list to the registries that you trust to contain valid images, and that you want applications to be able to import from. Users with permission to create images or ImageStreamMappings from the API are not affected by this policy. Typically only cluster administrators have the appropriate permissions.
    3
    additionalTrustedCA: A reference to a config map containing additional certificate authorities (CA) that are trusted during image stream import, pod image pull, openshift-image-registry pullthrough, and builds. The namespace for this config map is openshift-config. The format of the config map is to use the registry hostname as the key, and the PEM certificate as the value, for each additional registry CA to trust.
    4
    registrySources: Contains configuration that determines whether the container runtime allows or blocks individual registries when accessing images for builds and pods. Either the allowedRegistries parameter or the blockedRegistries parameter can be set, but not both. You can also define whether or not to allow access to insecure registries or registries that allow registries that use image short names. This example uses the allowedRegistries parameter, which defines the registries that are allowed to be used. The insecure registry insecure.com is also allowed. The registrySources parameter does not contain configuration for the internal cluster registry.
    Note

    When the allowedRegistries parameter is defined, all registries, including the registry.redhat.io and quay.io registries and the default OpenShift image registry, are blocked unless explicitly listed. If you use the parameter, to prevent pod failure, you must add the registry.redhat.io and quay.io registries and the internalRegistryHostname to the allowedRegistries list, as they are required by payload images within your environment. Do not add the registry.redhat.io and quay.io registries to the blockedRegistries list.

    When using the allowedRegistries, blockedRegistries, or insecureRegistries parameter, you can specify an individual repository within a registry. For example: reg1.io/myrepo/myapp:latest.

    Insecure external registries should be avoided to reduce possible security risks.

  2. To check that the changes are applied, list your nodes: 

    $ oc get nodes

    Example output

    NAME                                         STATUS                     ROLES                  AGE   VERSION
ip-10-0-137-182.us-east-2.compute.internal   Ready,SchedulingDisabled   worker                 65m   v1.25.4+77bec7a
ip-10-0-139-120.us-east-2.compute.internal   Ready,SchedulingDisabled   control-plane          74m   v1.25.4+77bec7a
ip-10-0-176-102.us-east-2.compute.internal   Ready                      control-plane          75m   v1.25.4+77bec7a
ip-10-0-188-96.us-east-2.compute.internal    Ready                      worker                 65m   v1.25.4+77bec7a
ip-10-0-200-59.us-east-2.compute.internal    Ready                      worker                 63m   v1.25.4+77bec7a
ip-10-0-223-123.us-east-2.compute.internal   Ready                      control-plane          73m   v1.25.4+77bec7a

9.2.1. Adding specific registries

You can add a list of registries, and optionally an individual repository within a registry, that are permitted for image pull and push actions by editing the image.config.openshift.io/cluster custom resource (CR). OpenShift Container Platform applies the changes to this CR to all nodes in the cluster.

When pulling or pushing images, the container runtime searches the registries listed under the registrySources parameter in the image.config.openshift.io/cluster CR. If you created a list of registries under the allowedRegistries parameter, the container runtime searches only those registries. Registries not in the list are blocked.

Warning

When the allowedRegistries parameter is defined, all registries, including the registry.redhat.io and quay.io registries and the default OpenShift image registry, are blocked unless explicitly listed. If you use the parameter, to prevent pod failure, add the registry.redhat.io and quay.io registries and the internalRegistryHostname to the allowedRegistries list, as they are required by payload images within your environment. For disconnected clusters, mirror registries should also be added.

Procedure

  1. Edit the image.config.openshift.io/cluster CR: 

    $ oc edit image.config.openshift.io/cluster

    The following is an example image.config.openshift.io/cluster CR with an allowed list: 

    apiVersion: config.openshift.io/v1
kind: Image
metadata:
  annotations:
    release.openshift.io/create-only: "true"
  creationTimestamp: "2019-05-17T13:44:26Z"
  generation: 1
  name: cluster
  resourceVersion: "8302"
  selfLink: /apis/config.openshift.io/v1/images/cluster
  uid: e34555da-78a9-11e9-b92b-06d6c7da38dc
spec:
  registrySources: 1
    allowedRegistries: 2
    - example.com
    - quay.io
    - registry.redhat.io
    - reg1.io/myrepo/myapp:latest
    - image-registry.openshift-image-registry.svc:5000
status:
  internalRegistryHostname: image-registry.openshift-image-registry.svc:5000
    1
    Contains configurations that determine how the container runtime should treat individual registries when accessing images for builds and pods. It does not contain configuration for the internal cluster registry.
    2
    Specify registries, and optionally a repository in that registry, to use for image pull and push actions. All other registries are blocked.
    Note

    Either the allowedRegistries parameter or the blockedRegistries parameter can be set, but not both.

    The Machine Config Operator (MCO) watches the image.config.openshift.io/cluster resource for any changes to the registries. When the MCO detects a change, it triggers a rollout on nodes in machine config pool (MCP). The allowed registries list is used to update the image signature policy in the /etc/containers/policy.json file on each node. Changes to the /etc/containers/policy.json file do not require the node to drain.

Verification

  • Enter the following command to obtain a list of your nodes: 

    $ oc get nodes

    Example output 

    NAME               STATUS   ROLES                  AGE   VERSION
<node_name>        Ready    control-plane,master   37m   v1.27.8+4fab27b

    1. Run the following command to enter debug mode on the node: 

      $ oc debug node/<node_name>

    2. When prompted, enter chroot /host into the terminal: 

      sh-4.4# chroot /host

    3. Enter the following command to check that the registries have been added to the policy file: 

      sh-5.1# cat /etc/containers/policy.json | jq '.'

      The following policy indicates that only images from the example.com, quay.io, and registry.redhat.io registries are permitted for image pulls and pushes:

      Example 9.1. Example image signature policy file

      {
   "default":[
      {
         "type":"reject"
      }
   ],
   "transports":{
      "atomic":{
         "example.com":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "image-registry.openshift-image-registry.svc:5000":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "insecure.com":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "quay.io":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "reg4.io/myrepo/myapp:latest":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "registry.redhat.io":[
            {
               "type":"insecureAcceptAnything"
            }
         ]
      },
      "docker":{
         "example.com":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "image-registry.openshift-image-registry.svc:5000":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "insecure.com":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "quay.io":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "reg4.io/myrepo/myapp:latest":[
            {
               "type":"insecureAcceptAnything"
            }
         ],
         "registry.redhat.io":[
            {
               "type":"insecureAcceptAnything"
            }
         ]
      },
      "docker-daemon":{
         "":[
            {
               "type":"insecureAcceptAnything"
            }
         ]
      }
   }
}
Note

If your cluster uses the registrySources.insecureRegistries parameter, ensure that any insecure registries are included in the allowed list.

For example: 

spec:
  registrySources:
    insecureRegistries:
    - insecure.com
    allowedRegistries:
    - example.com
    - quay.io
    - registry.redhat.io
    - insecure.com
    - image-registry.openshift-image-registry.svc:5000

9.2.2. Blocking specific registries

You can block any registry, and optionally an individual repository within a registry, by editing the image.config.openshift.io/cluster custom resource (CR). OpenShift Container Platform applies the changes to this CR to all nodes in the cluster.

When pulling or pushing images, the container runtime searches the registries listed under the registrySources parameter in the image.config.openshift.io/cluster CR. If you created a list of registries under the blockedRegistries parameter, the container runtime does not search those registries. All other registries are allowed.

Warning

To prevent pod failure, do not add the registry.redhat.io and quay.io registries to the blockedRegistries list, as they are required by payload images within your environment.

Procedure

  1. Edit the image.config.openshift.io/cluster CR: 

    $ oc edit image.config.openshift.io/cluster

    The following is an example image.config.openshift.io/cluster CR with a blocked list: 

    apiVersion: config.openshift.io/v1
kind: Image
metadata:
  annotations:
    release.openshift.io/create-only: "true"
  creationTimestamp: "2019-05-17T13:44:26Z"
  generation: 1
  name: cluster
  resourceVersion: "8302"
  selfLink: /apis/config.openshift.io/v1/images/cluster
  uid: e34555da-78a9-11e9-b92b-06d6c7da38dc
spec:
  registrySources: 1
    blockedRegistries: 2
    - untrusted.com
    - reg1.io/myrepo/myapp:latest
status:
  internalRegistryHostname: image-registry.openshift-image-registry.svc:5000
    1
    Contains configurations that determine how the container runtime should treat individual registries when accessing images for builds and pods. It does not contain configuration for the internal cluster registry.
    2
    Specify registries, and optionally a repository in that registry, that should not be used for image pull and push actions. All other registries are allowed.
    Note

    Either the blockedRegistries registry or the allowedRegistries registry can be set, but not both.

    The Machine Config Operator (MCO) watches the image.config.openshift.io/cluster resource for any changes to the registries. When the MCO detects a change, it drains the nodes, applies the change, and uncordons the nodes. After the nodes return to the Ready state, changes to the blocked registries appear in the /etc/containers/registries.conf file on each node.

Verification

  • Enter the following command to obtain a list of your nodes: 

    $ oc get nodes

    Example output 

    NAME                STATUS   ROLES                  AGE   VERSION
<node_name>         Ready    control-plane,master   37m   v1.27.8+4fab27b

    1. Run the following command to enter debug mode on the node: 

      $ oc debug node/<node_name>

    2. When prompted, enter chroot /host into the terminal: 

      sh-4.4# chroot /host

    3. Enter the following command to check that the registries have been added to the policy file: 

      sh-5.1# cat etc/containers/registries.conf

      The following example indicates that images from the untrusted.com registry are prevented for image pulls and pushes:

      Example output

      unqualified-search-registries = ["registry.access.redhat.com", "docker.io"]

[[registry]]
  prefix = ""
  location = "untrusted.com"
  blocked = true

9.2.2.1. Blocking a payload registry

In a mirroring configuration, you can block upstream payload registries in a disconnected environment using a ImageContentSourcePolicy (ICSP) object. The following example procedure demonstrates how to block the quay.io/openshift-payload payload registry.

Procedure

  1. Create the mirror configuration using an ImageContentSourcePolicy (ICSP) object to mirror the payload to a registry in your instance. The following example ICSP file mirrors the payload internal-mirror.io/openshift-payload: 

    apiVersion: operator.openshift.io/v1alpha1
kind: ImageContentSourcePolicy
metadata:
  name: my-icsp
spec:
  repositoryDigestMirrors:
  - mirrors:
    - internal-mirror.io/openshift-payload
    source: quay.io/openshift-payload

  2. After the object deploys onto your nodes, verify that the mirror configuration is set by checking the /etc/containers/registries.conf file:

    Example output

    [[registry]]
  prefix = ""
  location = "quay.io/openshift-payload"
  mirror-by-digest-only = true

[[registry.mirror]]
  location = "internal-mirror.io/openshift-payload"

  3. Use the following command to edit the image.config.openshift.io custom resource file: 

    $ oc edit image.config.openshift.io cluster

  4. To block the payload registry, add the following configuration to the image.config.openshift.io custom resource file: 

    spec:
  registrySources:
    blockedRegistries:
     - quay.io/openshift-payload

Verification

  • Verify that the upstream payload registry is blocked by checking the /etc/containers/registries.conf file on the node.

    Example output

    [[registry]]
  prefix = ""
  location = "quay.io/openshift-payload"
  blocked = true
  mirror-by-digest-only = true

[[registry.mirror]]
  location = "internal-mirror.io/openshift-payload"

9.2.3. Allowing insecure registries

You can add insecure registries, and optionally an individual repository within a registry, by editing the image.config.openshift.io/cluster custom resource (CR). OpenShift Container Platform applies the changes to this CR to all nodes in the cluster.

Registries that do not use valid SSL certificates or do not require HTTPS connections are considered insecure.

Warning

Insecure external registries should be avoided to reduce possible security risks.

Procedure

  1. Edit the image.config.openshift.io/cluster CR: 

    $ oc edit image.config.openshift.io/cluster

    The following is an example image.config.openshift.io/cluster CR with an insecure registries list: 

    apiVersion: config.openshift.io/v1
kind: Image
metadata:
  annotations:
    release.openshift.io/create-only: "true"
  creationTimestamp: "2019-05-17T13:44:26Z"
  generation: 1
  name: cluster
  resourceVersion: "8302"
  selfLink: /apis/config.openshift.io/v1/images/cluster
  uid: e34555da-78a9-11e9-b92b-06d6c7da38dc
spec:
  registrySources: 1
    insecureRegistries: 2
    - insecure.com
    - reg4.io/myrepo/myapp:latest
    allowedRegistries:
    - example.com
    - quay.io
    - registry.redhat.io
    - insecure.com 3
    - reg4.io/myrepo/myapp:latest
    - image-registry.openshift-image-registry.svc:5000
status:
  internalRegistryHostname: image-registry.openshift-image-registry.svc:5000
    1
    Contains configurations that determine how the container runtime should treat individual registries when accessing images for builds and pods. It does not contain configuration for the internal cluster registry.
    2
    Specify an insecure registry. You can specify a repository in that registry.
    3
    Ensure that any insecure registries are included in the allowedRegistries list.
    Note

    When the allowedRegistries parameter is defined, all registries, including the registry.redhat.io and quay.io registries and the default OpenShift image registry, are blocked unless explicitly listed. If you use the parameter, to prevent pod failure, add all registries including the registry.redhat.io and quay.io registries and the internalRegistryHostname to the allowedRegistries list, as they are required by payload images within your environment. For disconnected clusters, mirror registries should also be added.

    The Machine Config Operator (MCO) watches the image.config.openshift.io/cluster CR for any changes to the registries, then drains and uncordons the nodes when it detects changes. After the nodes return to the Ready state, changes to the insecure and blocked registries appear in the /etc/containers/registries.conf file on each node.

Verification

  • To check that the registries have been added to the policy file, use the following command on a node: 

    $ cat /etc/containers/registries.conf

    The following example indicates that images from the insecure.com registry is insecure and is allowed for image pulls and pushes.

    Example output

    unqualified-search-registries = ["registry.access.redhat.com", "docker.io"]

[[registry]]
  prefix = ""
  location = "insecure.com"
  insecure = true

9.2.4. Adding registries that allow image short names

You can add registries to search for an image short name by editing the image.config.openshift.io/cluster custom resource (CR). OpenShift Container Platform applies the changes to this CR to all nodes in the cluster.

An image short name enables you to search for images without including the fully qualified domain name in the pull spec. For example, you could use rhel7/etcd instead of registry.access.redhat.com/rhe7/etcd.

You might use short names in situations where using the full path is not practical. For example, if your cluster references multiple internal registries whose DNS changes frequently, you would need to update the fully qualified domain names in your pull specs with each change. In this case, using an image short name might be beneficial.

When pulling or pushing images, the container runtime searches the registries listed under the registrySources parameter in the image.config.openshift.io/cluster CR. If you created a list of registries under the containerRuntimeSearchRegistries parameter, when pulling an image with a short name, the container runtime searches those registries.

Warning

Using image short names with public registries is strongly discouraged because the image might not deploy if the public registry requires authentication. Use fully-qualified image names with public registries.

Red Hat internal or private registries typically support the use of image short names.

If you list public registries under the containerRuntimeSearchRegistries parameter (including the registry.redhat.io, docker.io, and quay.io registries), you expose your credentials to all the registries on the list, and you risk network and registry attacks. Because you can only have one pull secret for pulling images, as defined by the global pull secret, that secret is used to authenticate against every registry in that list. Therefore, if you include public registries in the list, you introduce a security risk.

You cannot list multiple public registries under the containerRuntimeSearchRegistries parameter if each public registry requires different credentials and a cluster does not list the public registry in the global pull secret.

For a public registry that requires authentication, you can use an image short name only if the registry has its credentials stored in the global pull secret.

The Machine Config Operator (MCO) watches the image.config.openshift.io/cluster resource for any changes to the registries. When the MCO detects a change, it drains the nodes, applies the change, and uncordons the nodes. After the nodes return to the Ready state, if the containerRuntimeSearchRegistries parameter is added, the MCO creates a file in the /etc/containers/registries.conf.d directory on each node with the listed registries. The file overrides the default list of unqualified search registries in the /etc/containers/registries.conf file. There is no way to fall back to the default list of unqualified search registries.

The containerRuntimeSearchRegistries parameter works only with the Podman and CRI-O container engines. The registries in the list can be used only in pod specs, not in builds and image streams.

Procedure

  1. Edit the image.config.openshift.io/cluster CR: 

    $ oc edit image.config.openshift.io/cluster

    The following is an example image.config.openshift.io/cluster CR: 

    apiVersion: config.openshift.io/v1
kind: Image
metadata:
  annotations:
    release.openshift.io/create-only: "true"
  creationTimestamp: "2019-05-17T13:44:26Z"
  generation: 1
  name: cluster
  resourceVersion: "8302"
  selfLink: /apis/config.openshift.io/v1/images/cluster
  uid: e34555da-78a9-11e9-b92b-06d6c7da38dc
spec:
  allowedRegistriesForImport:
    - domainName: quay.io
      insecure: false
  additionalTrustedCA:
    name: myconfigmap
  registrySources:
    containerRuntimeSearchRegistries: 1
    - reg1.io
    - reg2.io
    - reg3.io
    allowedRegistries: 2
    - example.com
    - quay.io
    - registry.redhat.io
    - reg1.io
    - reg2.io
    - reg3.io
    - image-registry.openshift-image-registry.svc:5000
...
status:
  internalRegistryHostname: image-registry.openshift-image-registry.svc:5000
    1
    Specify registries to use with image short names. You should use image short names with only internal or private registries to reduce possible security risks.
    2
    Ensure that any registries listed under containerRuntimeSearchRegistries are included in the allowedRegistries list.
    Note

    When the allowedRegistries parameter is defined, all registries, including the registry.redhat.io and quay.io registries and the default OpenShift image registry, are blocked unless explicitly listed. If you use this parameter, to prevent pod failure, add all registries including the registry.redhat.io and quay.io registries and the internalRegistryHostname to the allowedRegistries list, as they are required by payload images within your environment. For disconnected clusters, mirror registries should also be added.

Verification

  • Enter the following command to obtain a list of your nodes: 

    $ oc get nodes

    Example output 

    NAME                STATUS   ROLES                  AGE   VERSION
<node_name>         Ready    control-plane,master   37m   v1.27.8+4fab27b

    1. Run the following command to enter debug mode on the node: 

      $ oc debug node/<node_name>

    2. When prompted, enter chroot /host into the terminal: 

      sh-4.4# chroot /host

    3. Enter the following command to check that the registries have been added to the policy file: 

      sh-5.1# cat /etc/containers/registries.conf.d/01-image-searchRegistries.conf

      Example output

      unqualified-search-registries = ['reg1.io', 'reg2.io', 'reg3.io']

9.2.5. Configuring additional trust stores for image registry access

The image.config.openshift.io/cluster custom resource can contain a reference to a config map that contains additional certificate authorities to be trusted during image registry access.

Prerequisites

  • The certificate authorities (CA) must be PEM-encoded.

Procedure

You can create a config map in the openshift-config namespace and use its name in AdditionalTrustedCA in the image.config.openshift.io custom resource to provide additional CAs that should be trusted when contacting external registries.

The config map key is the hostname of a registry with the port for which this CA is to be trusted, and the PEM certificate content is the value, for each additional registry CA to trust.

Image registry CA config map example

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-registry-ca
data:
  registry.example.com: |
    -----BEGIN CERTIFICATE-----
    ...
    -----END CERTIFICATE-----
  registry-with-port.example.com..5000: | 1
    -----BEGIN CERTIFICATE-----
    ...
    -----END CERTIFICATE-----

1
If the registry has the port, such as registry-with-port.example.com:5000, : should be replaced with ...

You can configure additional CAs with the following procedure.

  1. To configure an additional CA: 

    $ oc create configmap registry-config --from-file=<external_registry_address>=ca.crt -n openshift-config
    $ oc edit image.config.openshift.io cluster
    spec:
  additionalTrustedCA:
    name: registry-config

9.2.6. Configuring image registry repository mirroring

Setting up container registry repository mirroring enables you to do the following:

  • Configure your OpenShift Container Platform cluster to redirect requests to pull images from a repository on a source image registry and have it resolved by a repository on a mirrored image registry.
  • Identify multiple mirrored repositories for each target repository, to make sure that if one mirror is down, another can be used.

The attributes of repository mirroring in OpenShift Container Platform include:

  • Image pulls are resilient to registry downtimes.
  • Clusters in disconnected environments can pull images from critical locations, such as quay.io, and have registries behind a company firewall provide the requested images.
  • A particular order of registries is tried when an image pull request is made, with the permanent registry typically being the last one tried.
  • The mirror information you enter is added to the /etc/containers/registries.conf file on every node in the OpenShift Container Platform cluster.
  • When a node makes a request for an image from the source repository, it tries each mirrored repository in turn until it finds the requested content. If all mirrors fail, the cluster tries the source repository. If successful, the image is pulled to the node.

Setting up repository mirroring can be done in the following ways:

  • At OpenShift Container Platform installation:

    By pulling container images needed by OpenShift Container Platform and then bringing those images behind your company’s firewall, you can install OpenShift Container Platform into a datacenter that is in a disconnected environment.

  • After OpenShift Container Platform installation:

    Even if you don’t configure mirroring during OpenShift Container Platform installation, you can do so later using the ImageContentSourcePolicy object.

The following procedure provides a postinstallation mirror configuration, where you create an ImageContentSourcePolicy object that identifies:

  • The source of the container image repository you want to mirror.
  • A separate entry for each mirror repository you want to offer the content requested from the source repository.
Note

You can only configure global pull secrets for clusters that have an ImageContentSourcePolicy object. You cannot add a pull secret to a project.

Prerequisites

  • Access to the cluster as a user with the cluster-admin role.

Procedure

  1. Configure mirrored repositories, by either:

    • Setting up a mirrored repository with Red Hat Quay, as described in Red Hat Quay Repository Mirroring. Using Red Hat Quay allows you to copy images from one repository to another and also automatically sync those repositories repeatedly over time.

    • Using a tool such as skopeo to copy images manually from the source directory to the mirrored repository.

      For example, after installing the skopeo RPM package on a Red Hat Enterprise Linux (RHEL) 7 or RHEL 8 system, use the skopeo command as shown in this example: 

      $ skopeo copy \
docker://registry.access.redhat.com/ubi8/ubi-minimal@sha256:5cfbaf45ca96806917830c183e9f37df2e913b187adb32e89fd83fa455ebaa6 \
docker://example.io/example/ubi-minimal

      In this example, you have a container image registry that is named example.io with an image repository named example to which you want to copy the ubi8/ubi-minimal image from registry.access.redhat.com. After you create the registry, you can configure your OpenShift Container Platform cluster to redirect requests made of the source repository to the mirrored repository.

  2. Log in to your OpenShift Container Platform cluster.

  3. Create an ImageContentSourcePolicy file (for example, registryrepomirror.yaml), replacing the source and mirrors with your own registry and repository pairs and images: 

    apiVersion: operator.openshift.io/v1alpha1
kind: ImageContentSourcePolicy
metadata:
  name: ubi8repo
spec:
  repositoryDigestMirrors:
  - mirrors:
    - example.io/example/ubi-minimal 1
    - example.com/example/ubi-minimal 2
    source: registry.access.redhat.com/ubi8/ubi-minimal 3
  - mirrors:
    - mirror.example.com/redhat
    source: registry.redhat.io/openshift4 4
  - mirrors:
    - mirror.example.com
    source: registry.redhat.io 5
  - mirrors:
    - mirror.example.net/image
    source: registry.example.com/example/myimage 6
  - mirrors:
    - mirror.example.net
    source: registry.example.com/example 7
  - mirrors:
    - mirror.example.net/registry-example-com
    source: registry.example.com 8
    1
    Indicates the name of the image registry and repository.
    2
    Indicates multiple mirror repositories for each target repository. If one mirror is down, the target repository can use another mirror.
    3
    Indicates the registry and repository containing the content that is mirrored.
    4
    You can configure a namespace inside a registry to use any image in that namespace. If you use a registry domain as a source, the ImageContentSourcePolicy resource is applied to all repositories from the registry.
    5
    If you configure the registry name, the ImageContentSourcePolicy resource is applied to all repositories from a source registry to a mirror registry.
    6
    Pulls the image mirror.example.net/image@sha256:…​.
    7
    Pulls the image myimage in the source registry namespace from the mirror mirror.example.net/myimage@sha256:…​.
    8
    Pulls the image registry.example.com/example/myimage from the mirror registry mirror.example.net/registry-example-com/example/myimage@sha256:…​. The ImageContentSourcePolicy resource is applied to all repositories from a source registry to a mirror registry mirror.example.net/registry-example-com.

  4. Create the new ImageContentSourcePolicy object: 

    $ oc create -f registryrepomirror.yaml

    After the ImageContentSourcePolicy object is created, the new settings are deployed to each node and the cluster starts using the mirrored repository for requests to the source repository.

  5. To check that the mirrored configuration settings, are applied, do the following on one of the nodes.

    1. List your nodes: 

      $ oc get node

      Example output

      NAME                           STATUS                     ROLES    AGE  VERSION
ip-10-0-137-44.ec2.internal    Ready                      worker   7m   v1.25.0
ip-10-0-138-148.ec2.internal   Ready                      master   11m  v1.25.0
ip-10-0-139-122.ec2.internal   Ready                      master   11m  v1.25.0
ip-10-0-147-35.ec2.internal    Ready                      worker   7m   v1.25.0
ip-10-0-153-12.ec2.internal    Ready                      worker   7m   v1.25.0
ip-10-0-154-10.ec2.internal    Ready                      master   11m  v1.25.0

      The Imagecontentsourcepolicy resource does not restart the nodes.

    2. Start the debugging process to access the node: 

      $ oc debug node/ip-10-0-147-35.ec2.internal

      Example output

      Starting pod/ip-10-0-147-35ec2internal-debug ...
To use host binaries, run `chroot /host`

    3. Change your root directory to /host: 

      sh-4.2# chroot /host

    4. Check the /etc/containers/registries.conf file to make sure the changes were made: 

      sh-4.2# cat /etc/containers/registries.conf

      Example output

      unqualified-search-registries = ["registry.access.redhat.com", "docker.io"]
short-name-mode = ""

[[registry]]
  prefix = ""
  location = "registry.access.redhat.com/ubi8/ubi-minimal"
  mirror-by-digest-only = true

  [[registry.mirror]]
    location = "example.io/example/ubi-minimal"

  [[registry.mirror]]
    location = "example.com/example/ubi-minimal"

[[registry]]
  prefix = ""
  location = "registry.example.com"
  mirror-by-digest-only = true

  [[registry.mirror]]
    location = "mirror.example.net/registry-example-com"

[[registry]]
  prefix = ""
  location = "registry.example.com/example"
  mirror-by-digest-only = true

  [[registry.mirror]]
    location = "mirror.example.net"

[[registry]]
  prefix = ""
  location = "registry.example.com/example/myimage"
  mirror-by-digest-only = true

  [[registry.mirror]]
    location = "mirror.example.net/image"

[[registry]]
  prefix = ""
  location = "registry.redhat.io"
  mirror-by-digest-only = true

  [[registry.mirror]]
    location = "mirror.example.com"

[[registry]]
  prefix = ""
  location = "registry.redhat.io/openshift4"
  mirror-by-digest-only = true

  [[registry.mirror]]
    location = "mirror.example.com/redhat"

    5. Pull an image digest to the node from the source and check if it is resolved by the mirror. ImageContentSourcePolicy objects support image digests only, not image tags. 

      sh-4.2# podman pull --log-level=debug registry.access.redhat.com/ubi8/ubi-minimal@sha256:5cfbaf45ca96806917830c183e9f37df2e913b187adb32e89fd83fa455ebaa6

Troubleshooting repository mirroring

If the repository mirroring procedure does not work as described, use the following information about how repository mirroring works to help troubleshoot the problem.

  • The first working mirror is used to supply the pulled image.
  • The main registry is only used if no other mirror works.
  • From the system context, the Insecure flags are used as fallback.
  • The format of the /etc/containers/registries.conf file has changed recently. It is now version 2 and in TOML format.

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