Documentation on the images structure/how to debug invalid builds?

[Sergio Schvezov]

On Tue, Jun 09, 2015 at 08:31:10PM +0200, Sebastien Bacher wrote:
> Hey everyone,
> 
> The desktop team continues looking at getting a desktop-next image based
> on snappy going, we managed to get the a first successful build on i386
> today (amd64 fails in what looks like the copy of signed boot bits, that
> needs extra debugging)
> https://launchpad.net/~ubuntu-cdimage/+livefs/ubuntu/wily/ubuntu-desktop-next/+build/29166
> 
> The build is giving us a device and a rootfs tarball, we are having some
> difficulties combining those into a working image though, some help
> would be welcome...
> 
> I've some question:
> 
> - is there any documentation describing what the device and rootfs
> tarballs should contain? that would be useful to valid if the bits
> available at the url mentioned before are valid

I guess the s-i code is your best bet here into transforming these.

> - is there some documentation describing what a "built" image is looking
> like? (like partitions schemes/types, what they should contain to be a
> valid boot medium, etc)

This is the most there is https://developer.ubuntu.com/en/snappy/guides/
and within:

- https://developer.ubuntu.com/en/snappy/guides/filesystem-layout/
- https://developer.ubuntu.com/en/snappy/guides/oem/

> - what's the right way to build an image from those tarball? I've tried
> to build goget-ubuntu-touch with the changes from
> https://code.launchpad.net/~canonical-ci-engineering/goget-ubuntu-touch/local_image/+merge/260531
> then used
> "u-d-f core rolling --channel edge
> --device-part=livecd.ubuntu-desktop-next.device.tar.gz
> --image-part=livecd.ubuntu-desktop-next.rootfs.tar.gz -o wily.img""
> 
> that gives an img but it seems invalid, trying to but it in kvm returns
> a "not a bootable disk" error, trying to use a local kernel/initrd
> (suggested by mvo) doesn't work either, it complains about missing fstab
> and other issues...

It's because of the massaging s-i does which slangasek mentions.

> - should the grub configuration be part of the device tarball or
> generated by the image builder?
> (unsure if having a device tarball there is needed/right, ubuntu-core
> build doesn't have one)

Grub configuration is now done on u-d-f and snappy sides during build or
updates (true for 15.04 at least, subject to change for rolling).