Merge pull request #87839 from rohennes/OCPBUGS-34880

OCPBUGS-34880: Clarifying flow for disconnected with different registries for seed and target

Author: mburke5678

edge_computing/image_based_upgrade/cnf-image-based-upgrade-base.adoc

@@ -18,6 +18,8 @@ include::modules/cnf-image-based-upgrade-prep.adoc[leveloffset=+1]
 
 * xref:../../edge_computing/image_based_upgrade/preparing_for_image_based_upgrade/cnf-image-based-upgrade-prep-resources.adoc#cnf-image-based-upgrade-prep-resources[Creating ConfigMap objects for the image-based upgrade with {lcao}]
 
+* xref:../../openshift_images/image-configuration.adoc#images-configuration-registry-mirror-configuring_image-configuration[Configuring image registry repository mirroring]
+
 include::modules/cnf-image-based-upgrade-with-backup.adoc[leveloffset=+1]
 
 [role="_additional-resources"]

modules/cnf-image-based-upgrade-prep.adoc

@@ -10,6 +10,18 @@ When you deploy the {lcao} on a cluster, an `ImageBasedUpgrade` custom resource
 After you created all the resources that you need during the upgrade, you can move on to the `Prep` stage.
 For more information, see the "Creating ConfigMap objects for the image-based upgrade with {lcao}" section.
 
+[NOTE]
+====
+In a disconnected environment, if the seed cluster's release image registry is different from the target cluster's release image registry, you must create an `ImageDigestMirrorSet` (IDMS) resource to configure alternative mirrored repository locations. For more information, see "Configuring image registry repository mirroring". 
+
+You can retrieve the release registry used in the seed image by running the following command:
+
+[source,terminal]
+----
+$ skopeo inspect docker://<imagename> | jq -r '.Labels."com.openshift.lifecycle-agent.seed_cluster_info" | fromjson | .release_registry'
+----
+====
+
 .Prerequisites
 
 * You have created resources to back up and restore your clusters.