[systemd-devel] systemd-inhibit fails when run from a service file

[Amish]

(Resending because earlier one, date 26/11/2019, did not get any response)

Hello,

I have a small perl program which downloads something. While downloading 
it inhibits (blocks) shutdown, reboot etc.

The program runs as user "foo".

Roughly the code is something like this:

$ cat /home/foo/downloads/dnld.sh
#!/bin/bash
/usr/bin/systemd-inhibit 
--what=shutdown:sleep:idle:handle-power-key:handle-suspend-key:handle-hibernate-key:handle-lid-switch 
--who=Downloader '--why=Important download in progress' --mode=block 
/home/foo/downloads/dnld.pl

This works fine when I run from a user foo's shell.

$ /home/foo/downloads/dnld.sh &
$ systemctl --dry-run suspend
Operation inhibited by "Downloader" (PID 27441 "systemd-inhibit", user 
foo), reason is "Important download in progress".

But now I call same script via dnld.service file.

$ cat /etc/systemd/system/dnld.service
[Unit]
Description=Download files
After=network.target

[Service]
User=foo
Type=simple
WorkingDirectory=/home/foo/downloads
ExecStart=/home/foo/downloads/dnld.sh

When I start the service it gives "Failed to inhibit: Access denied" error.

# systemctl start dnld.service
# journalctl -u dnld.service
Nov 26 13:33:30 foo systemd[1]: Started Download files.
Nov 26 13:33:30 foo dnld.sh[27745]: Failed to inhibit: Access denied
Nov 26 13:33:30 foo systemd[1]: dnld.service: Main process exited, 
code=exited, status=1/FAILURE
Nov 26 13:33:30 foo systemd[1]: dnld.service: Failed with result 
'exit-code'.

If I change code to not call systemd-inhibit:

$ cat /home/foo/downloads/dnld.sh
#!/bin/bash
/home/foo/downloads/dnld.pl

Then service file runs fine.

# systemctl start dnld.service; sleep 30
# journalctl -u dnld.service
Nov 26 13:50:17 foo systemd[1]: Started Download files.
Nov 26 13:50:37 foo systemd[1]: dnld.service: Succeeded.

So how do I allow systemd-inhibit call when a script is called via 
systemd instead of directly?

Is this systemd bug or am I missing something in dnld.service file?

Amish