Does anyone know if the Atomic Host will auto update from 26->27 or is it a manual process?
The location of the F27 bits are separate from the F26 bits, so you'll have to manually add a new remote and then rebase to that new remote.
$ sudo ostree remote add --set=gpgkeypath=/etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-27-primary fedora-atomic-27 https://kojipkgs.fedoraproject.org/atomic/27
$ sudo rpm-ostree rebase fedora-atomic-27:fedora/27/x86_64/atomic-host
Static deltas are enabled from the last F26 commit to the F27 release which should reduce the amount of data you have to ship over. Just make sure your host is at the latest F26 release via `rpm-ostree upgrade` before doing the rebase operation.