This error occurs when your server can’t resolve domain names into IPs, meaning your DNS settings are broken. It might happen if /etc/resolv.conf is misconfigured or overwritten. Use cat /etc/resolv.conf to check and add a public resolver like 8.8.8.8 or 1.1.1.1. Persistent DNS failures might be caused by iptables rules, firewall blocks, or an overloaded resolver. Restarting the systemd-resolved service or flushing DNS with systemd-resolve --flush-caches can help in some cases.