Improvements to hostname support

[Lukas Märdian]

The Netplan hostname directives ("hostname", "use-hostname", and "send-hostname") are currently only supported by the systemd-networkd renderer.

Since many Ubuntu Core customers end up using the network-manager snap, it would make sense to enhance the network-manager renderer to support the same options.

In addition, Netplan currently lacks support for setting the static hostname (i.e. writing the hostname to /etc/hostname) which is supported by NetworkManager (see nmcli hostname).

Finally, it would be nice to have a way to specify via Netplan that an auto-generated hostname should be configured (e.g. using UUIDs or similar to how LXD auto-generates container names).

See also: FIEL-169 & FIEL-170

[Lukas Märdian (slyon)]

After some more discussion, we came to the impression that cloud-init should be used for managing the (static or auto-generated) hostname instead of netplan: https://cloudinit.readthedocs.io/en/latest/reference/modules.html#set-hostname

Would that work for you?

If not, should Netplan also be managing /etc/hosts?