Re: Incremental target images

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2018-08-27 09:44, Claudius Heine wrote:
> 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
> 

Hmm, I'm not seeing yet where the complication could come from. I would 
have expected the following:

- write a new image recipe include that takes a preexisting image in
   form of a rootfs as input (rather than using setup_root_file_system)

- create specialized images on top of that which depend on some base
   image recipe as well as additional IMAGE_INSTALL recipes and may come
   with own IMAGE_PREINSTALLs (always on top of base images)

- push all common IMAGE_PREINSTALLs into base image recipes, same for
   all IMAGE_INSTALLs

And done. What am I missing?

Jan