Bug#1014115: uninstall does not properly remove enablement symlinks

[Michael Biebl]

Am 30.06.22 um 16:13 schrieb Luca Boccassi:
> On Thu, 30 Jun 2022 at 15:08, Michael Biebl <biebl at debian.org> wrote:
>>
>> Am 30.06.22 um 14:26 schrieb Michael Biebl:
>>> This might be a bug in i-s-h, but filing against systemd-homed for
>>> now.
>>>
>>> systemd-homed.service:
>>> [Install]
>>> WantedBy=multi-user.target
>>> Alias=dbus-org.freedesktop.home1.service
>>> Also=systemd-homed-activate.service systemd-userdbd.service
>>>
>>> systemd-homed-activate.service:
>>> [Install]
>>> WantedBy=systemd-homed.service
>>> Also=systemd-homed.service
>>>
>>> → we have a circular dependency here, maybe deb-systemd-helper get's
>>> confused by that
>>
>>
>> I just checked that we can mitigate this issue by removing this circular
>> Also= dependency. It is indeed deb-systemd-helper getting confused by
>> that and as a result not writing proper state files to
>> /var/lib/systemd/deb-systemd-helper.
>> So the damage is already done during installation in postinst.
>> Thus raising to RC to warn users from installing systemd-homed atm.
>>
>> I propose a patch like the attached one, i.e. dropping the Also= from
>> systemd-homed-active.service. WDYT?

Are you against shipping this patch for the time being until we have a 
proper fix?

>> I've also cloned the issue for i-s-h, as we might want to fix that
>> properly. My perl is a bit rusty, so would appreciate help with that.
>>
>> @bluca: do you think the attached patch is suitable for upstream?
>>
>> I find this circular Also= dependency kinda odd, I have to admit.
> 
> I don't think so, this seems clearly a bug in i-s-h. Ideally we should
> really drop all of that and just use presets as RPMs do... but it's a
> lot of work.

We have i-s-h/deb-systemd-helper for a couple of reasons (none of which 
can be solved by presets afaics)

- distinction between uninstalled/purged state in Debian.
We want to ensure that if you have a install/remove/install sequence, 
the enablement state of the service is preserved.
For that we need to keep additional state, that is only removed on purge.
If we remove the enablement symlinks on remove, we can't preserve the state.
If we remove the enablement symlinks on purge, the service files are no 
longer around, so we can't do a proper cleanup.

- masking a service upon uninstallation
This is a sad reality, as packages still ship legacy SysV init scripts 
which are conffiles and would suddenly become active if a package is 
removed but not purged.

I certainly would like to get rid of i-s-h, but I don't see how that is 
doable.

Regards,
Michael


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