Ubuntu 20.04 and the netplan that is now normal

20.04 arrived in April and netplan is no longer the new thing — which means the older configuration people still copy from notes does nothing at all.

# /etc/netplan/01-netcfg.yaml
network:
  version: 2
  ethernets:
    ens3:
      addresses: [203.0.113.10/24]
      gateway4: 203.0.113.1
      nameservers: { addresses: [1.1.1.1, 9.9.9.9] }

# netplan try     applies, and reverts in 120s unless confirmed
# netplan apply

netplan try is the command that saves you on a remote machine: it applies the change and rolls back automatically if you do not confirm, so a mistake in an address does not lock you out. YAML indentation errors are the main failure mode and are reported reasonably well. 20.04 also moved to systemd-resolved by default, so /etc/resolv.conf is a symlink and editing it is undone on the next boot.