Bug#1057220: Looks like the systemctl links are gone but not the pm-utils ones

[Chris Hofstaedtler]

Hi everyone!

On Tue, Dec 12, 2023 at 03:08:49PM +0100, Helmut Grohne wrote:
[..
> Almost two weeks later, I'm back with what I hope is a solution.
[..]
> At the time of this writing, my preferred solution is restoring the lost
> files in postinst. Fortunately, they are all symlinks in the case of
> systemd-sysv, so restoring them is a rather simple matter. And this is
> what the attached systemd patch does.
[..]
> This is not the option I'm going for now. Rather, given that systemd can
> paper over the loss we can make the loss very unlikely by having
> molly-guard not declare Breaks against systemd-sysv. As a result, apt no
> longer sees a mutual conflict and no longer schedules temporary removal.
> Thus, the loss scenario (usually) does not happen (though systemd-sysv
> still mitigates it).

I think this is a good plan, even though this means quite a few
packages will have to do this in their maintainer scripts. I'll note
that all affected packages will have to cooperate.

[..]
>     /usr/sbin/halt -> /usr/sbin/halt.no-molly-guard

I think this is a bit of a problem. My understanding of
molly-guard's primary feature is to hide dangerous programs from
$PATH, to avoid execution by overworked (or otherwise unattentive)
operators.

Keeping the dangerous programs in $PATH, under a similar-enough name
that TAB-completion works, might be a serious downgrade in
functionality to molly-guard's audience.

I would suspect for other packages, like progress-linux-container,
it might be worse, if they expect to completely disable these
programs.

As said above, this is all speculation, but I want to point this
out, and maybe Francois can comment if this is acceptable for
molly-guard?

[..]
> So now I am attaching the result of my work. I invite people to review
> it (even though I understand that this is a complex matter). In
> particular, I am also interested in what kind of tests I should be
> performing in addition.

I've asked you before on IRC about the test cases I thought to be
the "interesting" ones and you pointed out they are already
covered by the attached testcases and they have a success outcome.

Chris