Comment # 1 on bug 1093460 from Richard Brown

(In reply to Paul Gonin from comment #0)
> I created a systemd timer with the following file
> 
> /etc/systemd/system/hourly-timer.target
> [Unit]
> Description=Hourly Timer Target
> StopWhenUnneeded=yes

This is not a valid timer. 

 - The filename does not end in .timer
 - The file does not contain a [Timer] nor an [Install] section

> systemd fails to start the timer:
> 
> # systemctl start /etc/systemd/system/hourly-timer.timer

This is not the valid syntax for enabling a timer

systemctl enable $foo.timer would be correct

By using the whole file path (and possibly an invalid one given this path ends
in .timer where your above file does not) systemctl is going to think you are
trying to reference a mount unit.

> Failed to start etc-systemd-system-hourly\x2dtimer.timer.mount: Unit
> etc-systemd-system-hourly\x2dtimer.timer.mount not found.

This is expected when using invalid syntax - systemctrl thought the filepath
was related to a mount point, so tried to find a systemd mount unit related to
that mount point.