Thanks @ferdnyc and @dans for the discussion here.
The /usr/share/rpm-ostree/treefile.json that is on the Fedora CoreOS nodes is copied in during the build process when composing the original Fedora CoreOS artifacts. It is not used at all during upgrades. It simply represents the input to rpm-ostree compose tree when originally built.
I’ll break my answer into two parts:
- Composing a custom tree
- You’d do this by executing CoreOS Assembler against the Fedora CoreOS config.
- I don’t think you actually want a custom tree. Looks like you just want to enable password auth via SSH Is that correct?