our minimal size requirements

[Oliver Grawert]

hi,

we currently recommend at least 4GB for an image, this is based on the
15.04 setup where we had two hardcoded readonly partitions of 1GB ...
plus the writable one.

with the all-snaps model where the two readonly partitons moved to loop
mounted squashfs images along with dropping the two readonly partitions
our size reqs. dropped significanly:

/dev/loop2      108M  108M     0
100% /snaps/canonical-dragon-linux.canonical/4.2.0-2014-generic-dragon410c
/dev/loop3       55M   55M     0
100% /snaps/ubuntu-core.canonical/16.04.0-7.arm64
/dev/loop4      768K  768K     0 100% /snaps/canonical-dragon/0.7.1

as you can see one of the readonly bits gets along with less than 200MB,
so all in all you could probably run a single purpose device (i.e.
something that just runs a single snap for embedded use) on around
1GB ...

i think we should adjust our numbers in docs accordingly for 16.04 ...

ciao
	oli