nslookup is a network administration tool for querying DNS servers. nslookup is very useful tool for debugging DNS record.
Query a domain name
Using the current ‘default’ DNS server:
# nslookup debian.org
Server: 62.210.16.6
Address: 62.210.16.6#53
Non-authoritative answer:
Name: debian.org
Address: 5.153.231.4
Using a specific DNS server:
# nslookup debian.org 8.8.8.8
Server: 8.8.8.8
Address: 8.8.8.8#53
Non-authoritative answer:
Name: debian.org
Address: 5.153.231.4
Query the MX Record
# nslookup -query=mx debian.org
Server: 62.210.16.6
Address: 62.210.16.6#53
Non-authoritative answer:
debian.org mail exchanger = 0 muffat.debian.org.
debian.org mail exchanger = 0 mailly.debian.org.
Here we have two MX (mail exchange) server for the zone debian.org
Query the NS Record
# nslookup -query=ns debian.org
Server: 62.210.16.6
Address: 62.210.16.6#53
Non-authoritative answer:
debian.org nameserver = dns1.easydns.com.
debian.org nameserver = debian1.dnsnode.net.
debian.org nameserver = dns4.easydns.info.
debian.org nameserver = sec1.rcode0.net.
debian.org nameserver = sec2.rcode0.net.
The NS record give the domain’s authoritative DNS servers list.
Query the SOA Record
# nslookup -query=soa debian.org
Server: 62.210.16.6
Address: 62.210.16.6#53
Non-authoritative answer:
debian.org
origin = denis.debian.org
mail addr = hostmaster.debian.org
serial = 2016092612
refresh = 1800
retry = 600
expire = 1814400
minimum = 600
The SOA record (start of authority) give information about the domain, it TTL, the e-mail address of the domain administrator, the domain serial number, etc…
Further Reading and sources