Document URL: 

* Gathering data about your cluster
  [ https://docs.openshift.com/container-platform/4.5/support/gathering-cluster-data.html ]

Section Number and Name: 

* Gathering data about your cluster for Red Hat Support
  [ https://docs.openshift.com/container-platform/4.5/support/gathering-cluster-data.html#support_gathering_data_gathering-cluster-data ]

Describe the issue: 

There is no mention about adding the required trusted CAs for the mirror before using ImageStream on the restricted network environments.
It's going to cause the import image command failure.

~~~
If your cluster is using a restricted network you must import the default must-gather image before running the oc adm must-gather command.

$ oc import-image is/must-gather -n openshift
~~~

Suggestions for improvement: 

Notify a procedure to add the required trusted CAs for the mirror together at the same section for must-gather.
The similar procedure is already provided in the other section[0], the procedure is also required for the section for must-gather.

[0] Using Cluster Samples Operator imagestreams with alternate or mirrored registries
    [ https://docs.openshift.com/container-platform/4.5/openshift_images/samples-operator-alt-registry.html#installation-restricted-network-samples_samples-operator-alt-registry ]
~~~
The cli, installer, must-gather, and tests imagestreams, while part of the install payload, are not managed by the Cluster Samples Operator.
These are not addressed in this procedure.
:

4. Add the required trusted CAs for the mirror in the cluster’s image configuration object:

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

Additional information: 

This issue is reported by CU.