[OE-core] Wic and "live" images

[Christopher Larson]

On Tue, May 24, 2016 at 1:16 PM, Ed Bartosh <ed.bartosh at linux.intel.com>
wrote:

> On Tue, May 24, 2016 at 12:56:39PM -0700, Christopher Larson wrote:
> > 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.
>
> I'm not sure I understand why it has to be machine-dependent setting in
> the .wks Can you give some example?


I don't understand the question. The .wks is machine specific by
definition. It includes knowledge of the expectations of the boot process
on the hardware the image is used on, what the boot device name is, etc.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics
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