DNS

Utilities

Utilities

host – DNS lookup utility

Forward query:

$ host dns.google
dns.google has address 8.8.8.8
dns.google has address 8.8.4.4
dns.google has IPv6 address 2001:4860:4860::8844
dns.google has IPv6 address 2001:4860:4860::8888

Reverse query:

$ host 8.8.8.8
8.8.8.8.in-addr.arpa domain name pointer dns.google.

Get MX records (mail server):

$ host -t MX constoso.com
constoso.com mail is handled by 10 mail2.namebrightmail.com.
constoso.com mail is handled by 10 mail1.namebrightmail.com.

Get NS record (who is authoritative for a domain):

$ host -t NS constoso.com
constoso.com name server ns1.namebrightdns.com.
constoso.com name server ns2.namebrightdns.com.

Get TXT records:

$ host -t TXT constoso.com
constoso.com descriptive text "google-site-verification=YourUniqueGoogleVerificationCode"
constoso.com descriptive text "v=spf1 a:smtpout1.namebrightmail.com a:smtpout2.namebrightmail.com ip4:216.87.78.66/31 include:namebrightmail.com -all"

With a specific DNS server:

$ host microsoft.com 8.8.8.8
Using domain server:
Name: 8.8.8.8
Address: 8.8.8.8#53
Aliases: 

microsoft.com has address 104.215.148.63
microsoft.com has address 40.76.4.15
microsoft.com has address 40.112.72.205
microsoft.com has address 40.113.200.201
microsoft.com has address 13.77.161.179
microsoft.com mail is handled by 10 microsoft-com.mail.protection.outlook.com.

resolvectl, resolvconf, systemd-resolve – Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services (SystemD)

query

$ resolvectl query debian.org
debian.org: 130.89.148.77
            149.20.4.15
            128.31.0.62

-- Information acquired via protocol DNS in 20.4ms.
-- Data is authenticated: no

$ resolvectl query 130.89.148.77
130.89.148.77: klecker-misc.debian.org

-- Information acquired via protocol DNS in 25.7ms.
-- Data is authenticated: no

To query DNS connected behind an interface

(for instance tun0 in the case of VPN):

resolvectl -i tun0 query server_behind_VPN

statistics

resolvectl statistics

flush-caches

Flush the DNS cache

resolvectl flush-caches

https://www.man7.org/linux/man-pages/man1/systemd-resolve.1.html

nslookup – query Internet name servers interactively

$ nslookup dns.google
Server:		127.0.0.53
Address:	127.0.0.53#53

Non-authoritative answer:
Name:	dns.google
Address: 8.8.8.8
Name:	dns.google
Address: 8.8.4.4
Name:	dns.google
Address: 2001:4860:4860::8888
Name:	dns.google
Address: 2001:4860:4860::8844

$ nslookup 8.8.8.8
8.8.8.8.in-addr.arpa	name = dns.google.

dig – DNS lookup utility

$ dig @8.8.8.8 debian.org

; <<>> DiG 9.11.3-1ubuntu1.12-Ubuntu <<>> @8.8.8.8 debian.org
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6191
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;debian.org.			IN	A

;; ANSWER SECTION:
debian.org.		124	IN	A	130.89.148.77
debian.org.		124	IN	A	128.31.0.62
debian.org.		124	IN	A	149.20.4.15

;; Query time: 13 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Thu Jun 18 11:07:16 CEST 2020
;; MSG SIZE  rcvd: 87