How to set up a proxy registry

[cornelius]

For installing CAP customers need to download container images on all nodes which run CAP components. To avoid having to download the same images multiple times a proxy registry caching images is required.

It also solves part of the use case where the system where CAP is set up doesn't have access to the Internet and because of this can't directly access the SUSE registry where the images are coming from. The proxy registry still would need to have access to the SUSE registry in this case, though.

We need to document how to set this up.

The terminology is a bit confusing here. We use "proxy registry" to describe a pull-through cache, i.e. a registry which either delivers the requested image if it already has it or first pulls it from another registry. Their also is the term mirror which sometimes is used in the same context. This would mean a registry which is actively populated with all images even before any of them is requested. In the upstream terminology and implementation these terms are mixed.

[cornelius]

More context is in https://bugzilla.suse.com/show_bug.cgi?id=1072941

[gaktive]

Air gap installs should still be looked at but this is only relevant for CaaSP. https://documentation.suse.com/suse-caasp/4.1/single-html/caasp-deployment/#_airgapped_deployment offers some guidance about what needs to be done at their end.