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Re: An old idea, brought back to life



On Mon, Dec 28, 1998 at 12:51:53AM +0100, Wichert Akkerman wrote:
> Previously Anthony Towns wrote:
> > What we don't have is some way to revoke that decision, say "Okay, that
> > was fun, but I want to go back to frozen. Buggy junk", and downgrade
> > the packages you just installed to ones that work
> A major problem is that dpkg does not support this currently: it does
> not check if all dependencies are still met if a package is downgraded.

Having Apt check that the dependencies are okay and not presenting anything
stupid to dpkg would go some way to solving this, I suppose.
 
> > The new Apt UI may have some support for this, but I'm not sure. (I'm
> > not quite sure what the UI-doc means when it discusses this functionality)
> What exactly don't you understand? Perhaps I can clear it up..

Okay. What seemed to me the best way for handling partial upgrading was
to do something like:

	default-distribution: slink

	libc6: default
	libstdc++-2.9: default
	libgtk1.1: slink
	foobar: unstable

...so that you could say "I want to follow slink, but I want the very latest
version of foobar, oh, and libgtk1.1 is different in potato, don't move away
from the slink one". Then apt would do clever things like, if foobar depends
on a later version of libc6 than that in slink, it'll just upgrade libc6,
but if it requires a later version of libgtk1.1, it'll just use an older
version of foobar (either what you've got, or the version from slink,
whichever's more recent).

Then, if you decide to set foobar back to "default", Apt should probably
notice that your installed version of foobar is more recent than your
requested version and at least give you the option of downgrading it,
and anything else that was forced to upgrade because of it.

So what I guess my question is:

	Apt supports a default distribution to follow, and lets you
	override that choice for various packages, right?

	What are the real choices for the above? Can you say "follow
	slink" or do you have to say "follow frozen", or is there another,
	better way of dealing with that?

	What does Apt do about conflicting suggestions (as in foobar
	requires a more recent version of bazquux)? Can Apt be arranged
	so in one case it upgrades both, and in another it keeps both
	at the old version?

	What support does Apt (the UI) have for downgrading? Will there
	be a dist-downgrade, or does that require a smarter dpkg before
	it's safe enough?

Cheers,
aj

-- 
Anthony Towns <aj@humbug.org.au> <http://azure.humbug.org.au/~aj/>
I don't speak for anyone save myself. PGP encrypted mail preferred.

``Like the ski resort of girls looking for husbands and husbands looking
  for girls, the situation is not as symmetrical as it might seem.''

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