78 mount points on armhf image

[Oliver Grawert]

hi,
Am Mittwoch, den 09.03.2016, 11:30 -0500 schrieb Mike Carifio:
> I might be sending this email to wrong list. Won't be the first time.
> Sorry if so.
> 
> Using these ubuntu section of these directions 
> https://developer.ubuntu.com/en/snappy/start/raspberry-pi-2/ and this
> image 
> https://people.canonical.com/~mvo/all-snaps/rpi2-all-snap.img.xz,
> I was able to install snappy on an rpi 2 model b. Other than some 
> fumbling around with sdcards, getting the display to show hdmi, etc, 
> this was easy enough for even me. Thank you.
> 
> Some follow on questions:
> 
> * mount | wc -l shows 78 (!) mount points. Yikes. Why? Guess I'll
> need 
> to brush up on partition mounting.
snappy uses a readonly image ... to have some files and dirs writable
we ue a "bind mount farm" (the alternative would be some kind of
overlayfs but this would enforce support for the chosen fs type in teh
kernel which we want to avoid) to actually mount these files into the
writable file space. while this is a bit ugly in the mount output, it
is very fine grained (so very secure) and also avoids extra filesystem
layers that potentially could affect performance.

> 
> * Unless I'm confused, it looks like /dev/mmcblk0p2 is mounted
> multiple 
> times.
> 
yes, this is how bind mounts are represented in the mount output.

> * Is there a rpi 3 model b image? As I understand it, 3 is armhf but
> 64 
> bits, so rpi2-all-snap won't work (although I did try).
the rpi3 while being a 64bit arch does not support 64bit at all yet,
you need to run 32bit userspace on it until the binary bootloader can
actually initialize the hardware in a 64bit mode, i assume broadcom
will soon provide the binary blobs for this.

as the person currently caring for the rpi images i took a brief look
last weekend.
 
snappy makes heavy use of u-boot features, the port of u-boot to the
rpi3 is still in very early stages (i assume it is only a matter of
weeks though). we also use a "close to mainline" kernel in snappy that
is currently missing some patches for the rpi3 i think. once these bits
are available i will try to make an rpi3 image (or even try to get the
current 32bit image to work on both devices).

ciao
	oli
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