[systemd-devel] How to source a variable file using systemd

[Soumya Koduri]

Thank you so much for your inputs.

-Soumya

On 10/27/2015 05:49 PM, Lennart Poettering wrote:
> On Tue, 27.10.15 16:05, Soumya Koduri (skoduri at redhat.com) wrote:
>
>> Hi,
>>
>> We have a use-case where in we have to read an environment variable (say
>> ${MY_ENV_FILE}) from a file (say /etc/myconfig) and source ${MY_ENV_FILE} to
>> read yet another environment variable (say ${MY_ENV_VAR} in our systemd
>> service file.
>
> Please use a shell script if you actually want the power of a
> shell. Unit files are explicitly designed to be a simple, non-turing
> complete language, with only minimal templating, and we have no
> intention to change that.
>
> If you want a scripting language, then please go for one, there's
> nothing wrong with invoking a shell script from ExecStart= that then
> does an "exec" for the real binary as last step.
>
> Of course, I think well written software doesn't require doing this,
> and supports good configuration files on its own, but if you have
> software that isn't that way, then by all means go ahead and write a
> shell script around it.
>
>>
>> I first tried out below --
>>
>> EnvironmentFile=/etc/myconfig
>> EnvironmentFile=${MY_ENV_FILE}
>> ...
>> ...
>> ExecStart='/bin/echo ${MY_ENV_VAR}'
>
> env vars are *only* expanded in ExecXYZ= lines. This is because they
> are determined at execution time from everything passed in from the
> manager, runtime env vars, env vars from the unit file and env vars
> from EnvironmentFile=.
>
> Lennart
>