[Samba] Upgrading Samba and Ubuntu: how to proceed?

[Giovanni Caini]

We have a DC with Ubuntu Server 16.04 and Samba 4.9.1 self-compiled. We
would like to update both Samba (to 4.11.6) and Ubuntu (to 18.04). Do you
have any advice on how to proceed, especially regarding the configuration
of the network interfaces, resolv.conf, etc...? First Samba or Ubuntu?
Ubuntu with do-release-upgrade?
Thanks so much,
Giovanni Caini