10 Linux DIG Command Examples for DNS Lookup--reference

;; AUTHORITY SECTION:
redhat.com. 600 IN NS ns1.redhat.com.
redhat.com. 600 IN NS ns4.redhat.com.
redhat.com. 600 IN NS ns3.redhat.com.
redhat.com. 600 IN NS ns2.redhat.com.

;; ADDITIONAL SECTION:
ns1.redhat.com. 600 IN A 209.132.186.218
ns2.redhat.com. 600 IN A 209.132.183.2
ns3.redhat.com. 600 IN A 209.132.176.100
ns4.redhat.com. 600 IN A 209.132.188.218

;; Query time: 160 msec
;; SERVER: 209.132.186.218#53(209.132.186.218)
;; WHEN: Thu Jan 12 10:22:11 2012
;; MSG SIZE rcvd: 180

9. Bulk DNS Query Using dig -f (and command line)

Query multiple websites using a data file:

You can perform a bulk DNS query based on the data from a file.

First,create a sample names.txt file that contains the website that you want to query.

$ vi names.txt
redhat.com
centos.org

Next,execute dig -f as shown below,which will perform DNS query for the websites listed in the names.txt file and display the output.

$ dig -f names.txt +noall +answer
redhat.com.             60      IN      A       209.132.183.81
centos.org.             60      IN      A       72.232.194.162

You can also combine record type with the -f option. The following example displays the MX records of multiple websites that are located in the names.txt file.

$ dig -f names.txt MX +noall +answer
redhat.com.             600     IN      MX      10 mx2.redhat.com.
redhat.com.             600     IN      MX      5 mx1.redhat.com.
centos.org.             3600    IN      MX      10 mail.centos.org.

Query multiple websites from dig command line:

You can also query multiple websites from the dig command line as shown below. The following example queries MX record for redhat.com,and NS record for centos.org from the command line

$ dig redhat.com mx +noall +answer centos.org ns +noall +answer
; <<>> DiG 9.7.3-RedHat-9.7.3-2.el6 <<>> redhat.com mx +noall +answer centos.org ns +noall +answer

;; global options: +cmd

redhat.com.             332     IN      MX      10 mx2.redhat.com.

redhat.com.             332     IN      MX      5 mx1.redhat.com.

centos.org.             3778    IN      NS      ns3.centos.org.

centos.org.             3778    IN      NS      ns4.centos.org.

centos.org.             3778    IN      NS      ns1.centos.org.

10. Use $HOME/.digrc File to Store Default dig Options

If you are always trying to view only the ANSWER section of the dig output,you don’t have to keep typing “+noall +answer” on your every dig command. Instead,add your dig options to the .digrc file as shown below.

$ cat $HOME/.digrc
+noall +answer

Now anytime you execute dig command,it will always use +noall and +answer options by default. Now the dig command line became very simple and easy to read without you have to type those options every time.

$ dig redhat.com
redhat.com.             60      IN      A       209.132.183.81
$ dig redhat.com MX

redhat.com.             52      IN      MX      5 mx1.redhat.com.

redhat.com.             52      IN      MX      10 mx2.redhat.com.

Linux provides several powerful administrative tools and utilities which will help you to manage your systems effectively. If you don’t know what these tools are and how to use them,you could be spending lot of time trying to perform even the basic administrative tasks. The focus of this course is to help you understand system administration tools,which will help you to become an effective Linux system administrator

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