[yocto] creating a ubuntu rootfs

[Christopher Hossack]

Hi,
I'm trying to create a Yocto kernel with a ubuntu-core rootfs. At the moment
I'm creating a core-image-base and then splatting an
ubuntu-core-12.04.5-core-armhf.tar.gz over the rootfs on the image. eg

Create a core-image-base image
$ bitbake core-image-base

Insert a sdcard and copy the core image on to it and then mount the rootfs
$ sudo dd if=~/core-image-base-imx6qsabresd.sdcard of=/dev/sdb bs=1M && sync
sudo mount /dev/sdb2 /mnt/sdcard/

Remove all files on the sdcard rootfs (eg sdb2) and then untar the unbuntu
core over the old rootfs, eg
$ cd /mnt/sdcard
$ sudo tar -xf ~/ubuntu-precise-12.04.3-armhf.com-20131129.tar.xz

Then copy the original fsl-image-base lib/modules/* & boot/* over the ubuntu
core rootfs
$ cd ~
$ sudo  mount -o loop -t ext3 core-image-base-imx6qsabresd.ext3 rootfs 
$ sudo rsync -artv rootfs/lib/modules/ /mnt/sdcard/lib/modules/
$ sudo rsync -artv rootfs/boot/ /mnt/sdcard/boot/

This all works, but I would really like to create a recipe that does all of
this work for me. But I believe my new recipe can't delete anything already
installed on the rootfs.

So I need to create a recipe that only installs /lib/modules/* /boot/* and
kernel source files (I also want to build kernel drivers on the target so I
guess I will also need recipe kernel-devsrc) on the rootfs.

I've looked at core-image-base (and others) and this seems to inherit
image.bbclass, but this adds a basic rootfs which will stop me from
splatting my ubuntu-core over it.

Can Yocto be configured to achieve this or should I stick to my current
hack?

Cheers

Chris



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