03.02.2021 22:25, Benjamin Berg пишет: > On Wed, 2021-02-03 at 20:47 +0300, Andrei Borzenkov wrote: >> 03.02.2021 00:25, Benjamin Berg пишет: >>> On Tue, 2021-02-02 at 22:50 +0300, Andrei Borzenkov wrote: >>>> 02.02.2021 17:59, Lennart Poettering пишет: >>>>> >>>>> Note that Requires= in almost all cases should be combined with >>>>> an >>>>> order dep of After= onto the same unit. >>>> >>>> Years ago I asked for example when Requires makes sense without >>>> After. >>>> Care to show it? I assume you must have use case if you say "in >>>> almost all". >>> >>> In the GNOME systemd units there are a few places where a Requires= >>> is >>> combined with Before=. >>> >> >> This is functionally completely equivalent to simply using >> Wants+Before. >> At least as long as you rely on *documented* functions. > > Requires= actually has the difference that the unit must become part of > the transaction (if it is not active already). So you get a hard > failure and appropriate logging if the unit cannot be added to the > transaction for some reason. > Oh, I said "documented" :) systemd documentation does not even define what "transaction" is. You really need to know low level implementation details to use it in this way. But thank you, I missed this subtlety. Of course another reason could be stop behavior. >> Care to show more complete example and explain why Wants does not >> work in this case? > > Wants= would work fine. I think it boils down to whether you find the > extra assertions useful. The Requires= documentation actually suggests > using Wants= exactly to avoid this. > > Benjamin >
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