How to register a third-level domain in hostname and hosts on Scaleway servers?

Question

Network administration

How to assign hostname and hosts to a third-level domain ( server.<domain name>.com ) on Scaleway servers ?..
Correcting the hosts and hostname files will not work - they are overwritten when the server is restarted.
Correcting the server name in the Scaleway console also does not work, you can only enter Latin letters and dashes ...
I tried to replace the metadata in the process on the server, then deleted the hosts and hostname - after rebooting everything is the same.
Technical support unsubscribes: We do not provide assistance services ( nah then they are needed at all? )...
In general, specialists, only hope is on you! ..

Answer 1

hostnamectl set-hostname srv.domain.com
reboot

If reset, see cloud-init settings
replace
with
preserve_hostname: true

Answer 2

Replaced
with
command hostnamectl set-hostname ... executed, but after reboot the hostname file was overwritten again
where else to dig?

Answer 3

Disable clod init