protect again time-machine rollbacks?

[moscicki]

An afterthought of #5387: suppose the sync folder is not excluded from the time machine backup and the system is rolled back. All the changes would be propagated to the server which is probably not what the user wants.

Is there a way to protect agains backup rollbacks and let the user decide what to do (start from scratch or propagate current state)?

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[SamuAlfageme]

@moscicki hm, I think preventing this would be a really nice enhancement for the desktop client (not only on OS X) but yeah. Actually found myself in a similar situation not so long ago and ended up having to restore things from server.

This would need some design though, e.g. first solution that occurred to me would be to detect the modification time of the folder sync connections (as they're retained in Time Machine) and compare to server's, but it's not that easy since this metadata might be completely different in both sides.

[ckamm]

Maybe something about seeing mtimes moving backwards?

[moscicki]

Quickly thinking about it I see two mechanisms:

You could have some extra protection if you keep track of the sync client activity in both sync folder and in the configuration directory and correlate them. It would allow you to detect the situation when the sync folder last activity does not match the one stored in the config. That would work for setup which I have seen which is to include config directory in the time machine but exclude sync folder from it.

Another mechanism is also possible but it would require to uniquely identify the client to the server (e.g. with uuid). If you keep the last mtime of the sync journal file of uniquely identified client on the server then you can see that it goes back in time in case of the restore from backup.

[andrewperry]

I have restored my whole computer from a time machine backup from a couple of weeks ago and now there's a lot of frequently used folders that are not completing a sync. I assume this is related to this issue?