classic mode (v1)

[Mark Shuttleworth]

On 23/11/15 17:28, Gustavo Niemeyer wrote:
> The agreement in the sprint was to use an overlay, IIRC. You might remember
> us discussing this inside the glassy room, where we talked about the fact
> this is similar in nature to how the live CD works.
>
> It sounds like there's a distinction being driven there which I don't quite
> follow, though. The overlay-on-classic-snap-content is still a one-time
> exercise until reset. (?)

Based on Pitti's feedback on overlays, I think we come out at:

 * the classic filesystem is read-write in the "classic" framework's
writeable space
 * this filesystem will initially be close to the current core snap (if
we unpack that plus delta)
 * that filesystem will drift relative to the core snap, based on
relative updates and deb installs
 * that filesystem is persistent until reset
 * for now, no processes persist in the classic dimension when the user
exits the classic shell

I think it's likely that unpacking the core OS snap plus a delta is the
fastest way to make that filesystem given what's available on the
machine (the delta will be a small download). Initially this might be
implemented as a debootstrap or even just unpacking the LXD images we
publish (from which the Core OS snap is derived).

Mark