Document link:
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/using_image_mode_for_rhel_to_build_deploy_and_manage_operating_systems/creating-bootc-compatible-base-disk-images-with-bootc-image-builder_using-image-mode-for-rhel-to-build-deploy-and-manage-operating-systems#creating-iso-images-by-using-bootc-image-builder_creating-bootc-compatible-base-disk-images-with-bootc-image-builder

Section number and name:
4.8. Creating ISO images by using bootc-image-builder

Describe the issue:
I found the issue while building ISO images but it probably affects all image types.

All examples in docs just assume that building bootc images and converting them to VM images (AMI, ISO, Qcow2, and others) happens on hosts which are properly entitled and connected to the Internet, so they can connect to Red Hat RPM repositories and download packages, and also to Red Hat registries, to download bootc container images.

But for many customers such builds must happen in air-gapped environments, using private container registries, and RPM repository hosted in private web servers (created using reposync) or Red Hat Satellite. In these cases, how will bootc-image-builder (bib) get RPM repository settings?

I had incorrect settings, but my mistake was not apparent because building bootc images and RAW images with bib worked fine, it only failed when building ISO images. And I didn't know which settings were affecting bib, product docs say nothing about this.. Would they be the build host settings? Would bib require its own set of repo settings, like the image builder service does? I didn't know where to search for configuration errors or missing configurations;

Engineering explained that repo settings come from the bootc image itself – the image I'm building and adding to my ISO, not the base images from Red Hat – and from that I was able to find out that one of the /etc/yum.d/*.repo files in my image had an incorrect URL to its GPG key. We assume it worked for other image types becaue they load the GPG key only one, and reuse it for different repos (it's was same key for all of them), but the ISO image build tried to re-load the key for each repository.

For reference, this was my thread with engineering:
https://redhat-internal.slack.com/archives/C02CU30L7GF/p1742848143478569

Impact of this issue:

Inability to crate bootc images and convert them to VM images in air-gapped environments, where build hosts do not connect to the internet to download Red Hat product artifacts.

Suggestions for improvement:

Add to the sections that explain how to build bootc images and how to use bootc-image-builder to convert bootc images to VM images information about how each tool gets RPM repository settings.