Add hostname customization to config.toml

[yweiser-redseal]

Feature Request

Add support for setting the hostname of a bootc disk image via the config.toml customization file.

Current behavior

The config.toml customization schema does not support a hostname field.
Users cannot set a static hostname at image build time through bootc-image-builder.

Workarounds are fragile:

• Writing /etc/hostname in the Containerfile via RUN echo does not reliably
  survive the ostree /etc management layer
• tmpfiles.d works but requires knowledge of ostree internals
• cloud-init preserve_hostname still requires the file to exist at install time

Expected behavior

[customizations]
hostname = "myhost.domain"

Proposed implementation

bootc install supports injecting files into the target deployment before first
boot via the ostree deployment API. A hostname customization could write directly
to the deployment's /etc/hostname post-install, similar to how root-ssh-authorized-keys
is handled today.

Environment

• bootc-image-builder
• build_revision: a686afe
• build_time: 2026-06-18T11:23:37Z

[supakeen]

I'm confused; your 'expected behavior' and description is about the blueprints as used in image-builder but your proposed implementation references bootc (which is a different project)?

You also haven't actually provided your environment. Are you using image-builder or bootc-image-builder?

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Aside from this and assuming you want us to enable the customizations.hostname for bootc-based image builds. I don't recall why we didn't do that in the past. @achilleas-k do you remember, or is it someone we can just turn on?

[yweiser-redseal]

Aside from this and assuming you want us to enable the customizations.hostname for bootc-based image builds.

Yes, you are correct. My appologies, I thought i read bootc-image-builder was merged into image-builder. didnt realize they are still separate tools.

[supakeen]

Aside from this and assuming you want us to enable the customizations.hostname for bootc-based image builds.

Yes, you are correct. My appologies, I thought i read bootc-image-builder was merged into image-builder. didnt realize they are still separate tools.

Your bug report talks about bootc itself and its ostree backend, not that much about bootc-image-builder but now its clear 🙂