13.6 Performing DNS Lookups

The host utility is recommended for performing DNS lookups. Without any arguments, host displays a summary of its command-line arguments and options. For example, look up the IP address for host01:

$ host host01

Perform a reverse lookup for the domain name that corresponds to an IP address:

$ host 192.168.2.101

Query DNS for the IP address that corresponds to a domain:

$ host dns.us.mydoc.com

Use the -v and -t options to display verbose information about records of a certain type:

$ host -v -t MX  www.mydom.com
Trying "www.mydom.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49643
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;www.mydom.com.			IN	MX

;; ANSWER SECTION:
www.mydom.com.		135	IN	CNAME	www.mydom.com.acme.net.
www.mydom.com.acme.net. 1240 IN	CNAME	d4077.c.miscacme.net.

;; AUTHORITY SECTION:
c.miscacme.net.	2000	IN	SOA	m0e.miscacme.net. hostmaster.misc.com. ...

Received 163 bytes from 10.0.0.1#53 in 40 ms

The –a option (equivalent to -v -t ANY) displays all available records for a zone:

$ host -a www.us.mydom.com
Trying "www.us.mydom.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40030
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.us.mydom.com.			IN	ANY

;; ANSWER SECTION:
www.us.mydom.com.		263	IN	CNAME	www.us.mydom.acme.net.

Received 72 bytes from 10.0.0.1#53 in 32 ms

For more information, see the host(1) manual page.