[OE-core] Contents of non-rootfs partitions

[Ed Bartosh]

On Tue, Nov 22, 2016 at 12:54:52PM +0100, Kristian Amlie wrote:
> On 22/11/16 12:10, Patrick Ohly wrote:
> >> ...
> > 
> > All of these introduce some special mechanism. Let me propose something
> > that might integrate better with the existing tooling:
> > 
> > The "rootfs" directory gets redefined as representing the entire virtual
> > file system. When creating a disk image, it gets split up into different
> > partitions based on the image configuration.
> > 
> > For example, the /home or /data directories in the rootfs could hold the
> > content that in some image configurations goes into separate partitions.
> > 
> > The advantage of this approach is that the tooling for staging content
> > for image creation does not need to be changed. The same staged content
> > then can be used to create different images, potentially even using
> > different partition layouts.
> 
> That's a very good idea. I think it beats all of my suggestions!
> 
> > To implement this approach with wic, wic needs to be taught how to
> > exclude directories from the main rootfs. Ideally, the mkfs.* tools
> > should also support that without having to make an intermediate copy of
> > the files for a certain partition, but initially wic could create
> > temporary directory trees.
> 
> Yes, some work would be needed here, but ultimately it would be contained within wic and related tools, which is a good thing.
>

I support the idea. Let's discuss the details of implementation and
create a bug in bugzilla to track the development 

This can be done by extending existing rootfs plugin. It should be able
to do 2 things:

- populate content of one rootfs directory to the partition. We can
  extend syntax of --rootfs-dir parameter to specify optional directory path to use

- exclude rootfs directories when populating partitions. I'd propose to
  introduce --exclude-dirs wks parser option to handle this.

Example of wks file with proposed new options:
part /     --source rootfs --rootfs-dir=core-image-minimal       --ondisk sda --fstype=ext4 --label root --align 1024 --exclude-dirs data --exclude-dirs home
part /data --source rootfs --rootfs-dir=core-image-minimal:/home --ondisk sda --fstype=ext4 --label data --align 1024
part /home --source rootfs --rootfs-dir=core-image-minimal:/data --ondisk sda --fstype=ext4 --label data --align 1024

Does this make sense?

Any other ideas?

--
Regards,
Ed