Hi, maybe it makes more sense to use "EnvironmentFile" parameter in the OpenDKIM systemd.service file:
--- /lib/systemd/system/opendkim.service.orig 2017-01-21 07:45:58.000000000 +0200 +++ /lib/systemd/system/opendkim.service 2017-06-08 17:02:34.632978678 +0300 @@ -5,10 +5,11 @@ [Service] Type=forking +EnvironmentFile=-/etc/default/opendkim PIDFile=/var/run/opendkim/opendkim.pid User=opendkim UMask=0007 -ExecStart=/usr/sbin/opendkim -P /var/run/opendkim/opendkim.pid -p local:/var/run/opendkim/opendkim.sock +ExecStart=/usr/sbin/opendkim -P /var/run/opendkim/opendkim.pid -p $SOCKET Restart=on-failure ExecReload=/bin/kill -USR1 $MAINPID Uve
