Existing systems for disconnected data access and reconciliation are monolithic, complex and somewhat ad-hoc. In contrast, we demonstrate here a principled approach based on a general-purpose reconciliation engine. We describe the Reconcilable and Undoable File System, Rufis, implemented on top of the IceCube reconciler. IceCube is generic but supports application-specific reconciliation invariants. Consequently, the code for Rufis is quite small and simple, and the reconciliation logic is well separated from the main file system code. Furthermore, Rufis supports specialised reconciliation for files containing data of known types and enables ad-hoc user scenarios involving multiple applications.