Bug#939904: Temporary network disruption during upgrade

[Luca Boccassi]

On Thu, 2022-08-18 at 16:07 +0200, Raphaël Halimi wrote:
> Le 17/08/2022 à 00:36, Luca Boccassi a écrit :
> > > Personally I see this as a regression, since resolved used to be part of
> > > systemd and thus readily available without installing additional packages.
> > 
> > No support was provided before for resolved, it was completely inhert,
> > hence it is not a regression. It is a change in behaviour, and thus
> > noted in the NEWS file as expected.
> > 
> > > Yes, but this goal could be achieved by letting resolved in the main
> > > systemd package, and splitting only systemd-resolvconf in its own package.
> > > 
> > 
> > Having a single-file-package that is confusing and harder to find is
> > not something we want to do, unless there are extremely compelling
> > reasons for it. Supporting resolvconf is not one.
> 
> Could you at least address the temporary break in DNS resolution ? This 
> is still a serious bug, which would deserve its own bug with priority 
> grave (if not critical). Since systemd-resolved is mainly used on 
> servers, it could result in a very bad surprise for sysadmins when 
> bookworm is released.

No, it is not, because no integration nor support was provided before.
It was an inhert and disabled service and binary.
The NEWS file covers the change adequately for custom setups. Custom
setups are always at risk of breakage.

> Perhaps it could be fixed by promoting systemd-resolved to a recommends 
> (instead of suggests) in systemd, so that it's installed during the 
> upgrade ? Or don't stop the service if /etc/resolv.conf is symlinked to 
> /run/systemd/resolve/stub-resolv.conf, so that the admin has the time to 
> read the NEWS entry (which, again, didn't work on my system, whereas it 
> was supposed to be sent in an e-mail by apt-listchanges), and install 
> systemd-resolved before rebooting ?

That would make it de-facto the default resolver on Debian, and we
really don't want that at this stage. There appears to be some bug in
apt-listchanges when showing changelogs is enabled making it skip NEWS
files if a changelog for the same version was already displayed, and
there's not much we can do about it, it's a problem to be solved by
apt-listchanges.

> Also, I understand that you don't wish to revert your changes, but is 
> there a reason why resolvconf, openresolv and thus systemd-resolved 
> could coexist thanks to the alternatives system ? I know it would be 
> more work for maintainers of those three packages, but IMHO it would be 
> worth the effort.

Absolutely not, the alternatives system is a gigantic mess that should
have never existed in the first place. If you want to use openresolv,
install openresolv and remove resolved.

> And, last but not the least, I see that /etc/resolv.conf is now part of 
> systemd-resolved files, which means that it would be deleted when the 
> systemd-resolved package is removed from the system. I think it would 
> also deserve its own bug with some high priority

No, that's working as intended - you remove one resolver, you need to
install another one that provides it.

-- 
Kind regards,
Luca Boccassi
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