Re: [poky] [question]: Creating tailored image without standard rootfs files?

On Wed, 13 Dec 2023 at 19:11, Ross Burton <[email protected]> wrote:

> On 13 Dec 2023, at 15:57, Einar Gunnarsson via lists.yoctoproject.org
> <[email protected]> wrote:
> >
> > Hello,
> >
> > I basically want to be able to build an ext4 image for an extra
> partition that is not a rootfs.
> >
> > So I don't need the kernel, or /run /var /etc folders or anything like
> that.
> > Just a few packages are needed, but with a QT app on that partition,
> loads of dependencies are pulled in and I end up with +80 entries in the
> manifest.
> >
> > This was asked 10 years ago, but I still have the same issue now.
> > https://docs.yoctoproject.org/pipermail/yocto/2013-March/012804.html
> >
> > This image would then be used by wic as well as swupdate, as a non-root
> partition.
> > Are there some tweaks to actually build an image without pulling in
> everything needed for a rootfs*?
> > I tried making my own tweaked version of image.bbclass, but I got lost
> in the abstraction.
> >
> >
> > *) Building a basic container-test-image with a linux-dummy still has
> all the folders /bin /boot /dev /etc /home /lib /media /mnt /proc /run
> /sbin /sys /tmp /usr /var
> > and +20 entries in the manifest (17MB of stuff), just for a 12KB binary
> (/usr/bin/theapp).
>
> If you set PACKAGE_INSTALL in your image then you override the implicit
> packages which can pull in dependencies.
>

Right. I had packagegroup-core-ssh-openssh there, coming through
IMAGE_FEATURES.

Unsetting IMAGE_LINGUAS and IMAGE_FEATURES will ensure that you don’t get
> any surprising features or locales installed.
>

poky/meta-selftest/recipes-test/container-image/container-test-image.bb
does unset IMAGE_LINGUAS.
Clearing IMAGE_FEATURES was the issue, and that pulled in these 20+
packages.

With IMAGE_FEATURES="" there's only one package in the manifest, and the
only extra files are
./etc/ld.so.cache ./etc/timestamp   ./etc/version

The /var/{cache,lib} and /run and folders are still there, but the manifest
is clean and the uncompressed tarball went from 17MB to 20KB.
These I can just get rid of with some  ROOTFS_POSTPROCESS_COMMAND
shenanigans.

However, if you have a non-statically linked Qt app that will obviously
> depend on other pieces of the system (such as libqt, so libx11, etc etc).
> This is a policy choice for you though: should apps in this partition be
> self-contained (so they either pull in their deps, or are statically
> linked), or depend on the contents of the main rootfs?
>
> If the latter then you can either actually build one rootfs and use wic to
> split it into separate partitions, or define a dummy recipe that defines
> the “ABI” that your rootfs provides: this can RPROVIDES the names that you
> don’t want in the second partition (like libx11) and by installing that the
> dependencies will be satisfied.
>

I do want them to depend on the contents of the main rootfs. But splitting
them up only in the wic puts them in the rootfs.ext4.
That creates issues for dm-verity, swupdate and more. I would not like to
deal with those issues.

But at least I have a starting point with container-test-image.bb and
clearing those variables.
Thanks.


> Ross


-- 
Regards
Einar Jón