DNS lookup utility.

# To lookup the IP(s) associated with a hostname (A records):
dig +short <hostname.com>

# To lookup the mail server(s) associated with a given domain name (MX record):
dig +short <hostname.com> MX

# To get all types of records for a given domain name:
dig <hostname.com> ANY

# To specify an alternate DNS server to query (8.8.8.8 is google's public DNS):
dig @<8.8.8.8> <hostname.com>

# To perform a reverse DNS lookup on an IP address (PTR record):
dig -x <8.8.8.8>

# To find authoritative name servers for the zone and display SOA records:
dig +nssearch <hostname.com>

# To perform iterative queries and display the entire trace path to resolve a domain name:
dig +trace <hostname.com>