OCPBUGS-10270: Add a note that you have to include the default channel

Author: bergerhoffer

modules/oc-mirror-creating-image-set-config.adoc

@@ -52,9 +52,9 @@ mirror:
     packages:
     - name: serverless-operator                                     <7>
       channels:
-      - name: stable
+      - name: stable                                                <8>
   additionalImages:
-  - name: registry.redhat.io/ubi8/ubi:latest                        <8>
+  - name: registry.redhat.io/ubi8/ubi:latest                        <9>
   helm: {}
 ----
 <1> Add `archiveSize` to set the maximum size, in GiB, of each file within the image set.
@@ -63,8 +63,9 @@ mirror:
 <4> Set the channel to retrieve the {product-title} images from.
 <5> Add `graph: true` to generate the OpenShift Update Service (OSUS) graph image to allow for an improved cluster update experience when using the web console. For more information, see _About the OpenShift Update Service_.
 <6> Set the Operator catalog to retrieve the {product-title} images from.
-<7> Specify only certain Operator packages and channels to include in the image set. Remove this field to retrieve all packages in the catalog.
-<8> Specify any additional images to include in image set.
+<7> Specify only certain Operator packages to include in the image set. Remove this field to retrieve all packages in the catalog.
+<8> Specify only certain channels of the Operator packages to include in the image set. You must always include the default channel for the Operator package even if you do not use the bundles in that channel. You can find the default channel by running the following command: `oc mirror list operators --catalog=<catalog_name> --package=<package_name>`.
+<9> Specify any additional images to include in image set.
 +
 See _Image set configuration parameters_ for the full list of parameters and _Image set configuration examples_ for various mirroring use cases.