$ cat /etc/systemd/system/noip-duc.service
[Unit]
Description=No-IP Dynamic Update Client
After=network.target auditd.service

[Service]
EnvironmentFile=/etc/sysconfig/noip-duc
ExecStart=/usr/local/bin/noip-duc
Restart=on-failure
Type=simple

[Install]
WantedBy=multi-user.target

always fails at boot time with the message status=2/INVALIDARGUMENT

Here is an extract from the system log (a fuller extract is attached):

Mar 18 07:57:56 OaklandWeather.localdomain systemd[1]: Started noip-duc.service - No-IP Dynamic Update Client.
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: noip-duc.service: Main process exited, code=exited, status=2/INVALIDARGUMENT
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: noip-duc.service: Failed with result 'exit-code'.
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: noip-duc.service: Scheduled restart job, restart counter is at 1.
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: Stopped noip-duc.service - No-IP Dynamic Update Client.
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: Started noip-duc.service - No-IP Dynamic Update Client.
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: noip-duc.service: Main process exited, code=exited, status=2/INVALIDARGUMENT
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: noip-duc.service: Failed with result 'exit-code'.
Mar 18 07:57:58 OaklandWeather.localdomain systemd[1]: noip-duc.service: Scheduled restart job, restart counter is at 2.

How can I find out what the argument is with which systemd is invoking noip-duc, so I can understand why it is invalid at boot time but valid when the unit is started afterwards from the console? I would simply recompile it to output this, but noip-duc is written in the rust programming language, which I to lazy to learn for this one application.

--

Sincerely Jonathan Ryshpan <jonrysh@pacbell.net>

	We dance around in a ring and suppose
	But the secret sits in the center and knows.
	- Robert Frost