[OE-core] Best practices: Multiple images on one partition.

[Paul Barker]

On Wed, 15 Jan 2020 at 13:05, Ricardo Ribalda Delgado
<ricardo.ribalda at gmail.com> wrote:
>
> Hello
>
> I am trying to figure out the best way to achieve this. I have a
> system with a host and a target. The target netboots form the host and
> have a different package architecture.
>
> Usually I was solving this with one partition per image/machine,
> combined using a .wks file like:
>
> part /export --source rootfs --rootfs-dir=target-image  --fstype=ext4
> --label export --align 1024 --use-uuid --fsoptions defaults,ro
> --extra-space 400M
> part / --source rootfs --fstype=ext4 --label rootfs --align 1024
> --use-uuid --fsoptions defaults,ro --extra-space 400M
>
> and then calling wic file after generating both images. ("wic create....")
>
> This works fine, but now I need to combine both partitions into one.
> The reason is that the partition needs to play nice with the current
> OTA upgrade system.
>
> What would be the best way to do this?
>
> 1) Implement a new wic plugin, called something like muli-rootfs,
> where I can specify multiple rootfs and in which directory to unpack
> them
>
> 2) Implement a .bb file that combines the two images in one.
>
> do_install() {
>     tar -mzxf $HOST/host-image.tar.gz  -C ${D}/
>     tar -mzxf $HOST/target-image.tar.gz  -C ${D}/export
> }
>
> 3) Another way that I am not aware :)

I've recently added the `--include-path` option to wic on master which
may be helpful here:
https://git.openembedded.org/openembedded-core/commit/?id=d4cd27a9837426e809190548a83c6c7c76505114.
My use case was multiple rootfs copies on different partitions, with
extra files added to just one copy of the rootfs. But it may also be
useful for this case.

Thanks,
Paul