Linux Pocket Guide, 2nd Edition

Name

host — stdin  stdout  - file  -- opt  --help  --version

Synopsis

host [options] name [server]

The host command looks up the hostname or IP address of a remote machine by querying DNS.

$ host www.ubuntu.org
www.ubuntu.com has address 91.189.90.41
$ host 91.189.90.41
41.90.189.91.in-addr.arpa domain name pointer
 jujube.canonical.com.

It can also find out much more:

$ host -a www.ubuntu.org
Trying "www.ubuntu.org"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16652
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ...

;; QUESTION SECTION:
;www.ubuntu.org.                     IN      ANY

;; ANSWER SECTION:
www.ubuntu.org.      60      IN      CNAME   ubuntu.org.

though a full discussion of this output is beyond the scope of this book. The final, optional “server” parameter specifies a particular nameserver for the query:

$ host www.ubuntu.org ns2.dondominio.com
Using domain server:
Name: ns2.dondominio.com
Address: 93.93.67.2#53
Aliases: 

www.ubuntu.org is an alias for ubuntu.org.
ubuntu.org has address 147.83.195.55
ubuntu.org mail is handled by 10 mx2.upc.es.
ubuntu.org mail is handled by 10 mx1.upc.es.

To see all options, type host by itself.

Useful options

-a	Display all available information.
-t	Choose the type of nameserver query: A, AXFR, CNAME, HINFO, KEY, MX, NS, PTR, SIG, SOA, and so on.

Here’s an example of the -t option to locate MX records:

$ host -t MX redhat.com
redhat.com mail is handled by 5 mx1.redhat.com.
redhat.com mail is handled by 10 mx2.redhat.com.

If the host command doesn’t do what you want, ...