Editing Tornedo.tetrain.com Upgrade Plan (section)

== 5. Rollback per hop ==

* '''If <code><nowiki>leapp preupgrade</nowiki></code> reports inhibitors''': nothing has changed yet — resolve and re-run, or stop and reassess.
* '''If the conversion or reboot fails''': restore from the pre-hop snapshot (virtualized) or disk image (bare metal) — this is why the snapshot in step 1 of every hop is mandatory, not optional.
* '''If validation fails post-reboot''': same — restore the pre-hop snapshot rather than trying to hand-fix a partially-converted IPA install; IPA's directory/PKI state is not something to debug live on a domain controller.
* There is no "keep both old and new running" fallback in this approach (that's what the replica strategy would have given you) — the snapshot '''is''' the rollback mechanism here, so don't proceed past a hop without confirming the snapshot is actually restorable.