Comment # 19 on bug 929471 from Thomas Blume

I think this issue is the same as reported here:

https://lists.debian.org/debian-user/2015/03/msg00287.html

The kernel.hostname sysctl is set without domain:

-->--
dg-linux:~ # sysctl -a | grep hostname
kernel.hostname = dg-linux
--<--

This is then used as the transient hostname by systemd.
The hostname call is correcting this:

-->--
dg-linux:~ # hostname -F /etc/hostname
dg-linux:~ # sysctl -a | grep hostname
kernel.hostname = dg-linux.golden-consulting.com
--<--

It is also corrected when you remove the transient hostname via:

hostnamectl --transient set-hostname ""

This will then use the correct static hostname.

The question is, what is setting kernel.hostname to the wrong value?