[yocto] Yocto Doubts

[Nicolas Dechesne]

On Tue, May 14, 2013 at 6:11 PM, varun bhatnagar <varun292006 at gmail.com>wrote:

> I am trying to understand Yocto build process and I have couple of
> doubts.....
>

based on your questions, i think you need to read a bit more about the
Yocto documentation. I definitely recommend that you carefully watch (or
read) at least the following links:

-
https://www.yoctoproject.org/tools-resources/videos/yocto-project-update-elc-2012
-
https://www.yoctoproject.org/docs/current/yocto-project-qs/yocto-project-qs.html
- http://www.slideshare.net/marcelolorenzati/yocto-iua-2012
- http://www.slideshare.net/rossburton/the-yocto-project



> 1) After specifying the architecture in local.conf when I give bitbake -k
> core-image-minimal the build process gets kicked off.
>                                     My doubt is how are the executables
> getting cross compiled. Is cmake getting called anywhere? How is the whole
> process linked?
>

based on your configuration, the cross compiler is either compiled on the
host first from source , or an 'external' toolchain is downloaded first.
the default configuration is to build the cross compiler first. Then all
components are cross compiled using the cross compiler. It doesn't matter
if you have another cross compiler *already* installed on your machine,
this one won't be used. how components are built is dictated by their
'recipe'. it could be cmake, make, autoconf, or anything else.


>
> 2) While building it executes some 1465 tasks which are packages written
> in recipe files and fetches them from internet. Will these be included in
> the image which will be created? If I want to restrict any package from
> getting downloaded how can I do that?
>

an 'image' is generated by 'aggregating' (binary) packages. packages are
built from recipes. there is generally 1 recipe for each 'source'
component, that can generate 1 or more 'packages'. in order to build a
recipe there are many 'tasks' needed like fetching the source code,
applying patches, configuration , compiling, packaging, ... so 1465 is the
sum of all the tasks, it doesn't mean that there are 1465 packages in the
image.

you can control very precisely what you want to put in your image.
'core-image-minimal' is a sample image provided in OE/yocto, but you are
free to either customize this image, or create your own image. For that, I
recommend looking at
http://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html, and
more precisely if you care about customizing images at
http://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html#usingpoky-extend-customimage
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