Please add a combined_squashfs_sha256 field for LXD consumption of the squashfs images

Stephane,

The root.tar.xz file will go away during the yakkety development cycle and the combined_sha256 value will refer to the squashfs root. Rather than adding combined_squahshfs_sha256 I propose adding an item named 'root_ftype' with a value of 'root.tar.xz' or 'squashfs' to indicates to which the combined_sha256 applies.

rcj: That'd be fine.

And when you say "within the cycle", you mean, "we already did it and everything is blowing up all over the place".

Current LXD and LXC are unable to get cloud images and that's causing test regressions for a lot of people.

The idea behind the separate combined_squashfs_sha256 was to allow for progressive migration from the .tar.xz to .squashfs format as new versions of the tools (LXC and LXD) get SRUed which would have allowed to do this change without breaking anyone.

But since you decided to break everyone anyway, it's indeed not needed.

Oh, one problem with your approach though. It means that we'll be stuck with .tar.xz for pre-Xenial, whereas with my suggested solution, recent LXD would be able to use squashfs on any release publishing the .squashfs and older LXD that doesn't know about squashfs would still work fine.

Not necessarily a problem, but it means that .squashfs for Xenial (and older) will remain effectively unused.

I will add items named 'combined_squashfs_sha256' and 'combined_rootxz_sha256' for the lxd metadata tar entries, the later being the same as combined_sha256.

combined_squashfs_sha256 entries are now available in simplestreams for yakkety @
http://cloud-images.ubuntu.com/daily/streams/v1/com.ubuntu.cloud:daily:download.json

Stephane, please verify the stream content.

Looks functional, my test code does successfully list the yakkety images and can download them fine.

Just spent a few minutes doing our side of this work, tested to be functional, supports all 3 possibles fields, does proper fallback and works when nested too.

https://github.com/lxc/lxd/pull/2146