Can you expand on that idea?  For Rumprun, it&#x27;s not very many minutes of work to set things up so that you have a lower readonly file system layer (immutable across restarts) and then a memory file system on top of that (for purposes of applications insisting to modify &quot;readonly&quot; files).  But, of course, it&#x27;s not very many minutes only if you know the ins and outs of the backend system, and that&#x27;s not the level of usability what we&#x27;re aiming for.  So, if writing &quot;readonly&quot; files is a widely desired feature, we should probably somehow support it as part of the general infrastructure in Rumprun so that it just works even if you don&#x27;t know the ins and out of the underlying system.