Re: Minimizing isar-image-base

[Alexander Smirnov <asmirnov@ilbers.de>]

Hi Jan,

On 20.08.2018 10:22, Jan Kiszka wrote:
> Hi all,
> 
> a couple of questions on what we pre-install into the de-facto standard 
> base image for everything that builds on Isar:
> 
> - Why do we pre-install init, but only for >= stretch?
> 

IIRC, for jessie and wheezy, the list of pre-installed packages was 
created based on attempt to boot the board. So it's just a result of 
experiment, no references to official Debian sources.

> - Why do we pre-install dbus?
> 

Again, IIRC, without dbus there was dirty boot log in QEMU, some 
services failed to start.

> - Can we make apt optional? Installing it as transient package by
>    default, e.g. What would happen if a downstream image then puts it
>    into PREINSTALL again? Should we filter IMAGE_TRANSIENT_PACKAGES
>    against IMAGE_PREINSTALL?

I could suppose how apt went to isar-image-base recipe, initially it was 
a copy of buildchroot one. So nobody actually cares about the list of 
packages, there was only one requirement - no error and warnings during 
image boot in QEMU.

In buildchroot apt is needed to populate the dependencies.

With current Isar implementation the apt is a must package for image. 
Let me explain why. Below is the whole chain to generate image:

1. At first, isar-debootstrap is called. This recipe fetches minimal 
*pure* Debian suite for specified architecture. It's stored in 
tmp/deploy folder.
2. Image generation is started from copying this pre-fetched suite to 
work folder.
3. Then you chroot to this *pure* minimal suite.
4. And finally all the additional packages in pre-install list are 
installed via apt-get.

So, the only way for current architecture - remove apt in post-build task.

Hope this a bit clarifies your questions.

> 
> Alternatively, we could define some isar-image-tiny that removes 
> packages from the base image, possibly also some that debootstrap pulls in.
> 
> Ideas, suggestions?
> 

I'd support you with this idea. For example sometimes I really need 
minimal QEMU image with just console, let's say 10-20MB of disk space 
and 2-3 minutes to build it.

But my proposal will be to start from requirements - which packages 
should go to tiny image and why. Otherwise we will have the same 
questions as above in 1-2 years :-)

Alex