Add links to pruning for disconnected OLM

Author: adellape

installing/installing-mirroring-installation-images.adoc

@@ -84,7 +84,35 @@ include::modules/olm-mirroring-catalog.adoc[leveloffset=+1]
 
 * xref:../operators/admin/olm-restricted-networks.adoc#olm-restricted-networks[Using Operator Lifecycle Manager on restricted networks]
 
-include::modules/olm-mirroring-catalog-prereqs.adoc[leveloffset=+2]
+[id="olm-mirror-catalog-prerequisites_installing-mirroring-installation-images"]
+=== Prerequisites
+
+Mirroring Operator catalogs for use with disconnected clusters has the following prerequisites:
+
+* Workstation with unrestricted network access.
+* `podman` version 1.9.3 or later.
+* If you want to filter, or _prune_, the default catalog and selectively mirror only a subset of Operators, see the following sections:
+** xref:../cli_reference/opm/cli-opm-install.adoc#cli-opm-install[Installing the opm CLI]
+** xref:../operators/admin/olm-restricted-networks.adoc#olm-pruning-index-image_olm-restricted-networks[Filtering a SQLite-based index image]
+ifndef::openshift-origin[]
+* If you want to mirror a Red Hat-provided catalog, run the following command on your workstation with unrestricted network access to authenticate with `registry.redhat.io`:
++
+[source,terminal]
+----
+$ podman login registry.redhat.io
+----
+endif::[]
+* Access to a mirror registry that supports
+link:https://docs.docker.com/registry/spec/manifest-v2-2/[Docker v2-2].
+* On your mirror registry, decide which namespace to use for storing mirrored Operator content. For example, you might create an `olm-mirror` namespace.
+* If your mirror registry does not have internet access, connect removable media to your workstation with unrestricted network access.
+* If you are working with private registries, including `registry.redhat.io`, set the `REG_CREDS` environment variable to the file path of your registry credentials for use in later steps. For example, for the `podman` CLI:
++
+[source,terminal]
+----
+$ REG_CREDS=${XDG_RUNTIME_DIR}/containers/auth.json
+----
+
 include::modules/olm-mirroring-catalog-extracting.adoc[leveloffset=+2]
 include::modules/olm-mirroring-catalog-colocated.adoc[leveloffset=+3]
 .Additional resources

modules/olm-mirroring-catalog-prereqs.adoc

@@ -23,9 +23,9 @@ ifndef::openshift-origin[]
 endif::[]
 
 [id="olm-pruning-index-image_{context}"]
-= Pruning a SQLite-based index image
+= Filtering a SQLite-based index image
 
-An index image, based on the Operator bundle format, is a containerized snapshot of an Operator catalog. You can prune an index of all but a specified list of packages, which creates a copy of the source index containing only the Operators that you want.
+An index image, based on the Operator bundle format, is a containerized snapshot of an Operator catalog. You can filter, or _prune_, an index of all but a specified list of packages, which creates a copy of the source index containing only the Operators that you want.
 
 ifeval::["{context}" != "olm-managing-custom-catalogs"]
 When configuring Operator Lifecycle Manager (OLM) to use mirrored content on restricted network {product-title} clusters, use this pruning method if you want to only mirror a subset of Operators from the default catalogs.