Referencing Other Environment Variables in Systemd

Question

Is is possible to reference other environment variables when setting new ones in systemd?

[Service]
EnvironmentFile=/etc/environment
Environment=HOSTNAME=$COREOS_PRIVATE_IPV4
Environment=IP=$COREOS_PRIVATE_IPV4
Environment=FELIX_FELIXHOSTNAME=$COREOS_PRIVATE_IPV4

The above code does not seem to be working.

Answer 1

In my case, the only way that worked to load the system environment variables into systemd script was to load them inside the script itself, like described here:

https://unix.stackexchange.com/questions/146995/inherit-environment-variables-in-systemd-docker-container

# Import our environment variables from systemd
for e in $(tr "\000" "\n" < /proc/1/environ); do
        eval "export $e"
done