[[!comment format=mdwn
 username="joey"
 subject="""comment 3"""
 date="2016-06-14T04:04:50Z"
 content="""
It might also be worth making the Sbuild properties know 
whether overlays are desired. Then they could make sure to set up the
config file with the needed lines, even if the wrong kernel is running.

I assume schroot fails to work in that configuration, so the properties
for it would fail and then the user would notice they need to add a
property to get a new enough kernel version..

It could be specified with another parameter to the Sbuild properties.
Or, you could add a pure Info property `useOverlays` and have the
Sbuild properties check if the Info has that set. This would also
let Schroot.overlaysInTmpfs require useOverlays and auto-enable them.

Most of the implementation of that:

	useOverlays :: Property (HasInfo + UnixLike)
	useOverlays = pureInfoProperty "use schroot overlays" (InfoVal UseOverlays)
	
	data UseOverlays = UseOverlays

	useOverlays :: Propellor Bool
	useOverlays = isJust . fromInfoVal
		<$> (askInfo :: Propellor (InfoVal UseOverlays))
"""]]
