Discovering

How To Know Your DNS Server?

1. GNU/Linux

1.1. First Attempt

In your command line, it’s just needed to type the following command which is the universal method for every distribution:

cat /etc/resolv.conf

Here’s the sample output on the end of the terminal:

   nameserver 8.8.8.8
   nameserver 192.168.0.1

Nevertheless, on many modern Linux distributions, the resolv.conf file might point to a local caching server, like the following output:

   # This is /run/systemd/resolve/stub-resolv.conf managed by man:systemd-resolved(8).
   # Do not edit.
   #
   # This file might be symlinked as /etc/resolv.conf. If you're looking at
   # /etc/resolv.conf and seeing this text, you have followed the symlink.
   #
   # This is a dynamic resolv.conf file for connecting local clients to the
   # internal DNS stub resolver of systemd-resolved. This file lists all
   # configured search domains.
   #
   # Run "resolvectl status" to see details about the uplink DNS servers
   # currently in use.
   #
   # Third party programs should typically not access this file directly, but only
   # through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
   # different way, replace this symlink by a static file or a different symlink.
   #
   # See man:systemd-resolved.service(8) for details about the supported modes of
   # operation for /etc/resolv.conf.

   nameserver 127.0.0.53
   options edns0 trust-ad
   search .

O endereço 127.0.0.53 é um IP de loopback local usado por sistemas Linux modernos (como Ubuntu) para o serviço systemd-resolved, que atua como um resolvedor DNS de cache local.

Ele substitui o antigo servidor DNS configurado diretamente no /etc/resolv.conf, agindo como um intermediário que encaminha consultas para servidores upstream, melhorando a eficiência e o cache local.

É um DNS stub listener que gerencia as requisições de DNS do sistema, sendo parte da rede local (127.0.0.0/8).

systemd-resolved: Este serviço escuta na porta 53 (127.0.0.53#53) para processar as consultas.

Conflitos: Pode causar conflitos se você tentar rodar outro servidor DNS local (como BIND ou Pi-hole) na mesma porta.

Como verificar: O comando resolvectl status mostra o status do resolvedor.

Como alterar: Para desativar e usar um servidor DNS tradicional, o serviço systemd-resolved deve ser desativado, o link simbólico /etc/resolv.conf desfeito e configurado manualmente.

1.2. Second Attempt

systemd-resolved is a systemd service that provides network name resolution to local applications via a D-Bus interface, stub resolver (127.0.0.53), and NSS service.

It improves performance with caching, supports DNSSEC validation, and handles split DNS for VPNs.

It is commonly enable by default replacing traditional /etc/resolv.conf manegament.

Also it is common in modern Ubuntu-based (Linux Mint, Pop!_OS, ZorinOS, and ElementaryOS) Fedora, and Debian.

Anyhoo, the resolvectl command provides detaild DNS information for all network interfaces:

resolvectl status

Output:

   Global
            Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
   resolv.conf mode: stub

   Link 2 (enp2s0f1)
      Current Scopes: none
            Protocols: -DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported

   Link 3 (wlp3s0)
      Current Scopes: DNS
            Protocols: +DefaultRoute -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
   Current DNS Server: 1.1.1.1
         DNS Servers: 1.1.1.1

It is also possible to filter the output for just the DNS information using grep:

   resolvectl status | grep "DNS Servers"

Output:

   DNS Servers: 1.1.1.1