[OE-core] Wic and "live" images

[Christopher Larson]

On Tue, May 24, 2016 at 12:51 PM, Ed Bartosh <ed.bartosh at linux.intel.com>
wrote:

> On Mon, May 23, 2016 at 08:13:28AM -0400, Ian Geiser wrote:
> >  > On Thu, May 19, 2016 at 05:52:45AM -0400, Ian Geiser wrote:
> >  > > Greetings, I am trying to learn "wic" and have been confused as how
> to create a "live" style image.  I am following "
> http://www.yoctoproject.org/docs/1.5.2/dev-manual/dev-manual.html#creating-partitioned-images"
> but am getting confused on the target to use to create the a file system
> that has a single squashfs file containing my root file system.
> >  > >
> >  > > My desired partition layout is as follows:
> >  > >       40MiB                 40MiB               300MiB
> >  > >
> +--------------------+-----------------+-----------------------------+
> >  > > |      BOOT (esp)    |    DATA (fat)   |          ROOT (live)
>   |
> >  > >
> +--------------------+-----------------+-----------------------------+
> >  > >
> >  > > BOOT - efi boot partition with kernel and initramfs
> >  > > DATA - generic fat filesystem to hold configuration files
> >  > > ROOT - an ext4 filesystem that contains a single os.img, which is a
> squashfs file.
> >  > >
> >  > > I have ROOT and DATA figured out but I am at a loss as how to
> generate the os.img file and copy it into ROOT.  If I generate the os.img
> file with bitbake and then use the "-r" option to manually supply a
> directory structure it works, but I would rather have it done from a wks
> file for automation reasons.
> >  > >
> >  > > Any hints?
> >  > I'd suggest to use wic image type and generate your image by bitbake.
> >  > You can find example wic-image-minimal.bb and wic-image-minimal.wks
> in ../meta-selftest/recipes-test/images/
> >  >
> > This is where I started.  I was able to make it work but not with my
> configuration above.  It looks like I can use a type of "fsimage" for my
> "ROOT" partition, but I have not been able to figure out the syntax there
> yet.  For "BOOT" I am at a complete loss.  In theory "bootimg-efi" but
> there doesn't seem to be a way to provide an initramfs.
>
> How about creating recipe to prepare content or your boot partition and
> then using --source rootfs --rootfs-dir=<your recipe> ?
> This is much more generic way of creating partitioned images from my
> point of view. Image recipes should take care of content and wic takes
> care of
> putting that content into partitions according to the partitioning
> scheme described in .wks
>
> Does it make sense for you?
>
> >
> >  > You can probably do the same by using wic plugins, but I'd not suggest
> >  > to go this way. Using wic image type is simpler, more consistent,
> easier to do and provides higher level of automation.
> >
> > Is using the wic image type and a plugin mutually exclusive?
> No, not at all. However, I personally found the way I described above
> more consistent, flexible and easy to implement and maintain.
>

The thing is, it's likely the machine/bsp setting the WKS_FILE, yet in
OE/yocto we prefer machine/distro/image to be orthogonal. If you're
injecting machine specific logic into an image, that image isn't going to
be generally useful for all machines, and so violates our philosophy.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics
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