[systemd-devel] Query regarding "EnvironmentFile"

[Andrei Borzenkov]

24.12.2015 03:48, Alex Crawford пишет:
> On 12/23, Jóhann B. Guðmundsson wrote:
>> The usual underlying cause of usage of Environment or EnvironmentFile in 
>> type units is more or less always due to the fact that the 
>> daemon/service cannot read configuration file on startup thus the answer 
>> is you would use a daemon that was written in a such manner it could 
>> read configuration file, generate that file and get rid of the extra 
>> administrator step of having administrators create and use drop-in's or 
>> am I missing something?
> 
> We are effectively using the drop-in to allow the user to map command line
> options to dynamic data. Since the user won't know things like IP addresses,
> they cannot write a traditional configuration file:
> 
>  $ cat static.conf
>  IP=1.2.3.4
> 
> They would instead have to write something like this:
> 
>  $ cat dynamic.conf
>  IP=COREOS_PUBLIC_IPV4
> 

I do not follow. You said that you are using separate service to
generate file that contains correct

IP=1.2.3.4

How does it matter whether this file is now read by systemd or your
daemon directly?

> Of course, the daemon would then need to understand how to follow this mapping
> and do the substitution itself. We instead decided to piggy-back on systemd and
> let it do the mapping for us.
> 

But systemd does not do any mapping - it simply passes along result of
mapping which another program has done.