Monday, 22 May 2023

Re: incoming change to task handling in livecd-rootfs in mantic

On Tue, 23 May 2023 at 03:34, Steve Langasek <> wrote:
On Mon, May 22, 2023 at 01:04:51PM +1200, Michael Hudson-Doyle wrote:
> Thinking about this a bit more... what is germinate actually for in this
> context? :-)

> The way packages from a seed end up in an image goes like this at the
> moment:

> 1. it is listed in the seed
> 2. germinate runs and puts the package and all its dependencies into a text
> file
> 3. live-build reads this text file and uses apt to install the packages
> (4. we run mimimize-manual at some point so removing a seeded package and
> running autoremove does something useful)

> The thing about this is, *apt* obviously knows how to find the dependencies
> of a package. Why don't we just shove the packages listed into the seed
> straight into the file live-build reads?

> (I suppose one answer might be to do with alternatives handling? cf
> -- does germinate do anything clever to
> satisfy alternatives with a minimal number of extra packages or anything
> like that?)

It does not.  Indeed, several of the recent seed changes made while landing
this were to fix the fact that germinate from livecd-rootfs (though not when
run on the archive) was seeding two conflicting implementations one of which
satisfies all the dependencies. 

(Actually this was a virtual package rather
than an alternative, but AFAIK it doesn't do anything clever with
alternatives either!)

Well potato potahto.
I would expect feeding the list directly to apt rather than using germinate
would result in some further changes to the exact packages included, which
would then need to be examined to confirm they're what we want, since there
are often multiple ways to resolve a seed.

There's also the fact that you'd be reimplementing germinate's own parsing
of the seeds and resolution of seed dependencies, so I'm not sure it's worth

Yes it's probably not worth it. But maybe we can lean this way for when we implement things in ubuntu-image (although I think that has support for running germinate already).

(One thing that would be nice, in addition to dropping the time-consuming
use of germinate at runtime,

The slow part IME is downloading the package lists, the computational part germinate only takes a few seconds. 
would be that today germinate silently ignores
listed packages that are unavailable, whereas apt would enforce correctness
of the list...)

That does sound like it would be an improvement.
> ((Clearly we need something like germinate to generate the component
> mismatches reports. But maybe not at image build time?))

That's already run on ubuntu-archive-toolbox independently of the image
builds, so would continue to do so.

Yes, I think my point here was that we can't just delete germinate completely.

Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
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