Re: Incremental target images

[Claudius Heine <claudius.heine.ext@siemens.com>]

On 2018-08-27 09:25, [ext] Claudius Heine wrote:
> Hi Jan,
> 
> On 2018-08-27 08:41, [ext] Jan Kiszka wrote:
>> Hi all,
>>
>> I was wondering if / how we could model the increasingly common case 
>> of building very similar target images more efficiently.
>>
>> A devel image, e.g., likely consists of almost the same base package 
>> set as the release image. It may only add further packages and maybe 
>> replace very few (like customization packages). When building both, we 
>> could save time - specifically when doing cross - by bootstrapping the 
>> baseline only once. We already do that for the debootstrap step, but 
>> not yet for further packages.
>>
>> What do you think? And how could that be modeled from user perspective?
> 
> That is not very easy.
> 
> A complex way this could be done by having a `common image` recipe that 
> depends on other image recipes to deploy their required package list,

What I meant by that is each image recipe writes its package list into 
its own text file in the 'deploy' directory.

> then figure out the common dependencies of all of them and build the 
> custom image.

s/custom/common/

Problem scenario here is:

  Image A: depends on A which depends on D
  Image B: depends on B which depends on D

Since D is not named in any recipes, but should be installed in the 
`common image` as automatically selected package (not as manual). This 
scripting is a bit tricky.

> Then those other image recipes depend of the `common 
> image` recipe in turn to create it, copy it and base their own 
> customizations on top.
> 
>  From a user perspective they would have to add their image recipes into 
> a global variable or bbappend, so that is available in the `common 
> image` recipe. The rest could be done in the image classes.
> 
> Cheers,
> Claudius

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