Teste da resolução de nomes DNS §

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O comando host [HOSTNAME] pode testar a conectividade do servidor de DNS.

[root@host ~]# host classroom.example.com
classroom.example.com has address 172.25.254.254
[root@host ~]# host 172.25.254.254
254.254.25.172.in-addr.arpa domain name pointer classroom.example.com.

O DHCP regrava automaticamente o arquivo /etc/resolv.conf quando as interfaces são iniciadas, a menos que você especifique ignore-auto-dns = yes no arquivo de configuração de interface relevante no diretório /etc/NetworkManager/system-connections/.

Estabeleça essa entrada usando o comando nmcli.

[root@host ~]# nmcli con mod "static-ens3" ipv4.ignore-auto-dns yes

Use o comando dig [HOSTNAME] para testar a conectividade do servidor de DNS.

[root@host ~]# dig classroom.example.com
 
; <<>> DiG 9.16.23-RH <<>> classroom.example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 3451
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 13, ADDITIONAL: 27
 
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: 947ea2a936353423c3bc0d5f627cc1ae7147460e10d2777c (good)
;; QUESTION SECTION:
;classroom.example.com.		IN	A
 
;; ANSWER SECTION:
classroom.example.com.	85326	IN	A	172.25.254.254
...output omitted...

Os comandos host e dig não exibem a configuração no arquivo /etc/hosts. Para testar o arquivo /etc/hosts, use o comando getent hosts [HOSTNAME].

[root@host ~]# getent hosts classroom.example.com
172.25.254.254  classroom.example.com

Referências §

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• Red Hat System Administration I