Re: 'IMAGE_FEATURES' in Isar

[Baurzhan Ismagulov <ibr@radix50.net>]

On Thu, Apr 12, 2018 at 05:35:17PM +0200, Claudius Heine wrote:
> Alex brought up the IMAGE_FEATURES idea and this thread just discuss it and
> to answer the questions: What else could IMAGE_FEATURES be used for? And
> does it make sense to use it to specify if the kernel should be part of the
> image or not?

Ah, now I see your point.

As I understand it, Alex's point is to introduce an additional, breve, binary
porcelain for the user. Adding or removing hairy IMAGE_INSTALL lines should be
hidden in the plumbing.

E.g., poky/meta/recipes-sato/images/core-image-sato.bb:

IMAGE_FEATURES += "splash package-management x11-base x11-sato \
ssh-server-dropbear hwcodecs"

When we have that many optional things, copy-pasting them in multiple recipes
would be an error-prone process and a maintenance problem due to duplication of
IMAGE_INSTALL += lines that have all to be updated if anything changes.

In our case, local.conf would have IMAGE_FEATURES = "kernel" by default. Of
course, we can only go in that direction if something like
IMAGE_FEATURES_isar-image-base = "" would work (maybe it does [1]). It isn't
very Isar-like, since Yocto is focused on one config at a time, and we
explicitly aim at multiple, diverse deliverables from the beginning. Ideally,
I'd like to see such binary porcelain in a recipe (not touching machine and
distro configs being the goal).


> >>   - Cleanup steps like localepurge, and apt-get clean
> >
> >Just do it always, as in your patches?
> 
> You meant the '*-configscripts.sh'?
> 
> AFAIK the purpose is to try to move most of this stuff out of there and into
> a 'system-setup-package' of sorts. At lease for all of those things, that
> don't require doing it at the end of everything.

Agree with the latter (e.g., root password, hostname).

Do I understand correctly that localepurge and apt-get clean have to be done at
the end? If yes, then they aren't suitable for system-setup-package. Then,
where should those go?

Regarding whether that should be done in IMAGE_FEATURES, my opinion is still
that specifically localepurge, apt-get clean should always be performed. IOW, I
don't think they belong to IMAGE_FEATURES.


> The rest of those steps (like those cleanup commands) should be split up
> into smaller scripts each with just one task and then trigger them via
> IMAGE_FEATURES after all packages were installed. Then the difference
> between raspbian and debian might just be some different entries in the
> IMAGE_FEATURES (or DISTRO_FEATURES) variable. At least thats my current idea
> here.

We can discuss those when we have a specific example.


> >>   - Removal of apt and other possible reduction tasks
> >
> >Additional recipe some images depend on?
> 
> Removal of apt and other reduction steps should be done after all packages
> are installed using apt. Doing that in some other recipe/debian package just
> doesn't work.

Ok, so it has to be a task. Yocto does it by default and provides
IMAGE_FEATURES += "package-management". I think mimicking that would be an
advantage here.


> >>The other question might be if having a kernel should be implemented as a
> >>IMAGE_FEATURE or rather a setting in the machine.conf?

I'd like to provide a binary way to customize it for every image without
touching machine or distro confs.


> >We already have it in IMAGE_INSTALL for isar-image-base. Doesn't it work if the
> >kernel is removed from there?
> 
> This is how I do it in the current "Optional kernel" patchset.

After I see the implementation, I think stacking complex lines in multiple
images has disadvantages compared to binary options.


References:

1. https://www.yoctoproject.org/docs/1.6/bitbake-user-manual/bitbake-user-manual.html#conditional-syntax-overrides


With kind regards,
Baurzhan.