[yocto] Image introspection

[Dimitris Tassopoulos]

Hi all,

I was thinking that the mail list shouldn't be only for problems and
questions and that from time to time, it would be nice to see some guides,
tutorials or success stories from people that follow the list.

Anyway, a few days ago someone had an issue with one of the BSPs I'm
maintaining and I wrote him a small guide on how to -try- to resolve future
issues like that. Then I thought that I haven't found a small tutorial
like this. Maybe it already exists, but nevertheless I haven't seen it.
Of course, those things are in the documentation, but they are documented
as individual tools (which is the correct thing to do), but it's not very
clear how to use all those things together to perform more complex tasks.

So, in my case the issue was that ofono was installed in the image and that
needed to be removed. Probably a lot of you already know the answer but for
me that I've never bothered with that I had to track it down how it got in
there.

Everything from now on assumes that you've setup up your bitbake environment
of your build with whatever setup scripts you're using (e.g.
*oe-init-build-env*)

There are several ways to do introspection on an image. For example,
let's say that you found a file in the in rootfs and you want to know which
recipe added that file. Then you can use this command:

oe-pkgdata-util find-path /usr/sbin/ofonod


*oe-pkgdata-util* is a utility in *poky/scripts/oe-pkgdata-util* and
`find-path` is pretty obvious what it does. This will return:

ofono: /usr/sbin/ofonod


So now you know that it's indeed the *ofono* recipe that adds this file.
Next,
you need how this did get in the image (probably some other dependency
because you didn't). Then you can use the `-g` parameter with bitbake like
this:

bitbake -g allwinner-image


This will create a file called `recipe-depends.dot`. This is a dot file that
has all the dependencies in the image. You can use the same command to get
the dependencies for a recipe, but now we care about the image.

Next step is to search in that file, why that key is there. Why is `-w` and
key is `-k`. You can always remember this as "-w-hy that -k-ey is there?"
and you
run this command:

oe-depends-dot -k ofono -w recipe-depends.dot


This will return the recipe that has this as dependency.


> Because: allwinner-image packagegroup-base


That means that the key is there because of allwinner-image (this is the
image
recipe, but it can be any other image) and because the *allwinner-image*
inherits the
*packagegroup-base*. So this packagegroup is the guilty.

Let's find this thing now. Get in the meta layer sources folder and run this

find . | grep packagegroup-base


This will return

> ./poky/meta/recipes-core/packagegroups/packagegroup-base.bb


Great. Open this file to an editor and find where is *ofono*. Gotcha, is in:

RDEPENDS_packagegroup-base-3g


Then it's the *packagegroup-base-3g* that does that. Probably that's a
recipe
or package group file, so you can run:

find . | grep packagegroup-base-3g


But you get nothing... Then probably this is declared somewhere a file with
another name, so let's search inside the files in the poky layer:

grep -nriI ackagegroup-base-3g


And we get:

poky/meta/recipes-core/packagegroups/packagegroup-base.bb:35:
> ${@bb.utils.contains("DISTRO_FEATURES", "3g", "packagegroup-base-3g", "",
> d)} \
> poky/meta/recipes-core/packagegroups/packagegroup-base.bb:73:
> ${@bb.utils.contains('COMBINED_FEATURES', '3g', 'packagegroup-base-3g',
> '',d)} \
> poky/meta/recipes-core/packagegroups/packagegroup-base.bb:122:
> d.setVar("ADD_3G", "packagegroup-base-3g")
> poky/meta/recipes-core/packagegroups/packagegroup-base.bb:316:SUMMARY_packagegroup-base-3g
> = "Cellular data support"
> poky/meta/recipes-core/packagegroups/packagegroup-base.bb:317:RDEPENDS_packagegroup-base-3g
> = "\
> poky/meta/recipes-core/packagegroups/packagegroup-base.bb:320:RRECOMMENDS_packagegroup-base-3g
> = "\



So it's actually in the same file that we already opened. Here you can
facepalm,
but we didn't know that, so this would be the procedure anyways to track it
down.
Now, search for *packagegroup-base-3g* inside the
*poky/meta/recipes-core/packagegroups/packagegroup-base.bb
<http://packagegroup-base.bb>*
and you see this line:

${@bb.utils.contains("DISTRO_FEATURES", "3g", "packagegroup-base-3g", "",
> d)} \


Therefore the *3g* in the *DISTRO_FEATURES* actually added *ofono*. That
means that,
we need to remove the *3g* string from our *DISTRO_FEATURES*.

To do that, add this to your build/conf/local.conf file

DISTRO_FEATURES_remove = " 3g"


Now just to be sure, run this to clean *ofono* from cache and everywhere
else:

bitbake -c cleanall ofono


And then rebuild the image:

bitbake image-name


Now you'll see that *ofono* won't b e downloaded or get built and it won't
be in your image.

I hope the above guide helps a bit.

I would be glad to get better suggestions or other people experience on
how they introspect their images and solve related issues.

Regards,
Dimitris
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