[systemd-devel] Antw: Re: Antw: Re: Re: [EXT] Re: Q: Querying units for "what provides" a target

[Ulrich Windl]

>>> Andrei Borzenkov <arvidjaar at gmail.com> schrieb am 09.09.2022 um 13:41 in
Nachricht
<CAA91j0VQADw8g5mmoFUOvy=YLF666Z_Y9uqYDgTfnmhSBne3rw at mail.gmail.com>:
> On Fri, Sep 9, 2022 at 2:13 PM Ulrich Windl
> <Ulrich.Windl at rz.uni-regensburg.de> wrote:
> ...
>> >
>> > If you are interested in services that pull in e.g. time-sync.target
>> > via Wants (or Requires) and order themselves before the target, you
>> > can use something like
>> > $ systemctl show time-sync.target -p WantedBy -p RequiredBy -p After
>> > RequiredBy=
>> > WantedBy=chrony.service
>> > After=chrony.service time-set.target
>>
>> It seems what I wanted to know is output by
>> # systemctl show -p After time-set.target
>> After=systemd-timesyncd.service
>> # systemctl show -p After time-sync.target
>> After=time-set.target ntp-wait.service
>>
>> However the "After=" is somewhat unexpected.
> 
> This is exactly what targets are about. The only usage for targets is
> to wait until something else becomes active and to do it they must
> come After something.
> 
>> And "-p WantedBy" is definitely
>> wrong (it will output units that "require the target", not the units 
> "providing
>> the target").
>>
> 
> There is no such thing as "units providing the target". Systemd
> documentation makes distinction between targets that Want other units
> ("active") and targets that are WantedBy other units ("passive"). It
> is expected that services "providing" passive targets have
> WantedBy=this-passive.target, otherwise passive targets will not be
> activated at all. So WantedBy is exactly correct in this case.

Hi!

But when I include it (as suggested) I get:
# systemctl show  -p WantedBy -p RequiredBy -p After time-sync.target
RequiredBy=
WantedBy=iotwatch at ROOT.service iotwatch at VPM.service iotwatch-generator.service ntp-wait.service systemd-timesyncd.service
After=time-set.target ntp-wait.service
---

Those iotwatch* units use "Before="; so is the WantedBy= incorrect for those?

Those units use:
Wants=nss-user-lookup.target time-sync.target paths.target
After=nss-user-lookup.target time-sync.target paths.target

Regards,
Ulrich