[systemd-devel] systemctl start second.service first.service

[Reindl Harald]

Am 11.01.2018 um 16:52 schrieb Uoti Urpala:
> On Thu, 2018-01-11 at 15:34 +0100, Reindl Harald wrote:
>> Am 11.01.2018 um 15:25 schrieb Uoti Urpala:
>>> I'd guess this is due to systemctl starting each listed unit
>>> independently rather than as a single transaction. Thus, the second
>>> version first starts second.service without first.service being active
>>> at all. Since there's only an After relationship, not Wants/Requires,
>>> second.service will immediately start. Then systemctl starts
>>> first.service; since second.service is already running, there's nothing
>>> the After relationship could affect
>>
>> but why?
>>
>> the one "After=" should be enough to have a clear ordering of stop/start
>> both as it happens in shutdown/boot
> 
> At boot, both would be started as part of the same transaction (same
> would happen here if you started a third.service that depended on both
> first.service and second.service, then second.service would always
> wait). Here second.service is just started individually, and systemd
> has no idea at that time that first.service is going to be running at
> all

that's a design error and don't follow the least surprise principle and 
until today i did not even consider that to be possible at all

> Given that, it really can't behave any differently (it can't delay
> the start of second.service to wait for first.service, when as far as
> it knows first.service may well never get started at all!). It's only
> after second.service is already running that it sees that first.service
> will be started, and at that point it's too late to make second.service
> wait. There really is nothing the init portion could do differently
> given the semantics of bare "After" (the behavior could be changed in
> the systemctl binary)
surely - systemctl could tell PID1 the whole list at once instead 
blindly fire up individual restart commands or *at least* it could make 
a ordering between the listed units from the restart command

it complete unexpected nonsense when i have two services which have a 
clear start ordering and may depend one from the other because you are 
even not able to do the right thing in your systemcl command because 
stop and start need the reverse ordner and so "restat a b c" is always 
wrong in one of both cases