Using The Dig Command
The command dig is a tool for querying DNS nameservers for information about host addresses, mail exchanges, nameservers, and related information. This tool can be used from any Linux (Unix) or Macintosh OS X operating system. The most typical use of dig is to simply query a single host.
Run The Command
dig crucialwebhost.com
View The Output
; <<>> DiG 9.3.4-P1 <<>> crucialwebhost.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35785
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 3
;; QUESTION SECTION:
;crucialwebhost.com. IN A
;; ANSWER SECTION:
crucialwebhost.com. 14400 IN A 208.43.148.151
;; Query time: 63 msec
;; SERVER: 67.228.89.10#53(67.228.89.10)
;; WHEN: Fri Apr 17 17:37:34 2009
;; MSG SIZE rcvd: 154
Understanding The Results
The opening section of dig's output tells us a little about itself (version 9.3.4) and the global options that are set (in this case, printcmd):
; <<>> DiG 9.3.4-P1 <<>> crucialwebhost.com
;; global options: printcmd
Here, dig tells us some technical details about the answer received from the DNS server. This section of the output can be toggled using the +[no]comments option—but beware that disabling the comments also turns off many section headers:
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35785
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 3
In the question section, dig reminds us of our query. The default query is for an Internet address (A):
;; QUESTION SECTION:
;crucialwebhost.com. IN A
Now we have our anwser, the address of crucialwebhost.com is 208.43.148.151:
;; ANSWER SECTION:
crucialwebhost.com. 14400 IN A 208.43.148.151
The final section of the default output contains statistics about the query; it can be toggled with the +[no]stats option:
;; Query time: 63 msec
;; SERVER: 67.228.89.10#53(67.228.89.10)
;; WHEN: Fri Apr 17 17:37:34 2009
;; MSG SIZE rcvd: 154
What can I find using the dig command?
dig will let you perform any valid DNS query, the most common of which are A (the IP address), TXT (text annotations), MX (mail exchanges), and NS nameservers.
Use the following command to get the addresses for crucialwebhost.com:
dig crucialwebhost.com A +noall +answer
Use the following command to get a list of all the mailservers for crucialwebhost.com:
dig crucialwebhost.com MX +noall +answer
Use the following command to get a list of authoritative DNS servers for crucialwebhost.com:
dig crucialwebhost.com NS +noall +answer
Use the following command to get a list of all the above in one set of results:
dig crucialwebhost.com ANY +noall +answer
Use the following command to query using a specific nameserver:
dig @ns1.crucialwebhost.com crucialwebhost.com
Use the following to trace the path taken:
dig crucialwebhost.com +trace
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