DNS Tools

nslookup

The "name server lookup" tool is used to query name servers to find information about resource records. Let's find where the name server for google.com is:

pete@icebox:~$ nslookup www.google.com
Server:         127.0.1.1
Address:        127.0.1.1#53

Non-authoritative answer:
Name:   www.google.com
Address: 216.58.192.4

dig

Dig (domain information groper) is a powerful tool for getting information about DNS name servers, it is more flexible than nslookup and great for troubleshooting DNS issues.

pete@icebox:~$ dig www.google.com

; <<>> DiG 9.9.5-3-Ubuntu <<>> www.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42376
;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; MBZ: 0005 , udp: 512
;; QUESTION SECTION:
;www.google.com.                        IN      A

;; ANSWER SECTION:
www.google.com.         5       IN      A       74.125.239.147
www.google.com.         5       IN      A       74.125.239.144
www.google.com.         5       IN      A       74.125.239.146
www.google.com.         5       IN      A       74.125.239.145
www.google.com.         5       IN      A       74.125.239.148

;; Query time: 27 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Sun Feb 07 10:14:00 PST 2016
;; MSG SIZE  rcvd: 123

DNS is a small idea with an enormous amount of machinery under it, and this section has stayed firmly on the small idea. Caching, resolvers, zone transfers, DNSSEC and the reasons that "it is always DNS" is a running joke among people who run systems are all past where these six lessons stop. ArchWiki's domain name resolution page is a good next step, since it deals with what is actually configured on a Linux machine.