Preparing for DNS outages

Create a resolved.conf.d file:

sudo mkdir /etc/systemd/resolved.conf.d/
sudo nano /etc/systemd/resolved.conf.d/dns_servers.conf

Add multiple fallback DNS:

[Resolve]
DNS=1.1.1.1 1.0.0.1 8.8.8.8 8.8.4.4

Then restart systemd-resolved:

sudo systemctl restart systemd-resolved

Now even if your provider messes up DNS setup or decides to block some addresses your servers will continue to function.