Linux / Unix: Find Out DNS Server IP Address / Names

by on October 3, 2012 · 6 comments· LAST UPDATED October 3, 2012

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How do I find out my DNS server IP address assiged my my ISP under Unix or Linux operating system using command prompt? How do I find preferred dns server under Debian / Ubuntu / Fedora Linux desktop system?

Tutorial details
DifficultyEasy (rss)
Root privilegesNo
RequirementsNone
Estimated completion timeN/A

Under Unix or Linux operating systems the resolver is used (set of routines in the C library) that provide access to the Internet Domain Name System (DNS). The resolver configuration file is located at /etc/resolv.conf location and it contains information that is read by the resolver routines the first time they are invoked by a process. Use the cat command or grep command to find out your dns server addresses as follows:

 
cat /etc/resolv.conf
 

Sample outputs:

# Generated by NetworkManager
nameserver 192.168.1.2
nameserver 192.168.1.3

In this example my dns server address are 192.168.1.2 and 192.168.1.3 in dot notation that the resolver should query. Currently name servers may be listed, one per keyword. If there are multiple servers, the resolver library queries them in the order listed. If no nameserver entries are present, the default is to use the name server on the local machine. The grep command can be used as follows:
$ grep --color nameserver /etc/resolv.conf
Sample outputs:

Linux / Unix: Ffind Preferred Dns Server Command

Fig.01: Linux / Unix: Find Preferred Dns Server Command

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{ 6 comments… read them below or add one }

1 Thad E Ginathom October 3, 2012 at 8:01 pm

For the cynical, who might think, “That is what the configuration file is telling the system to do, how can I be sure what it *is* doing, you can find out how your system resolves any given name using dig

$ dig http://www.ibm.com

; <> DiG 9.8.1-P1 <> http://www.ibm.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 46538
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.ibm.com. IN A

;; ANSWER SECTION:
http://www.ibm.com. 981 IN CNAME http://www.ibm.com.cs186.net.
http://www.ibm.com.cs186.net. 60 IN A 129.42.60.216

;; Query time: 870 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Thu Oct 4 01:26:31 2012
;; MSG SIZE rcvd: 80

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2 Jalal Hajigholamali October 4, 2012 at 12:11 pm

Hi,

Thanks a lot

simple and useful ..

Reply

3 Mac October 4, 2012 at 2:36 pm

Can someone help to explain to how use the color option but without using the case sensitive requirement like for example:

grep –color hostname /etc/sysconfig/network
no data output

grep –color HOSTNAME /etc/sysconfig/network
HOSTNAME=acct2.acme.com

is there a way in grep to get it to display regardless of case sensitive?

any help/advice would be great

Reply

4 JBruyet October 4, 2012 at 7:33 pm

man grep
that will give you -i, –ignore-case
Ignore case distinctions in both the PATTERN and the input files. (-i is specified by POSIX.)

man pages are your friend.

Thanks,

Joe B

Reply

5 Thad E Ginathom October 4, 2012 at 7:36 pm

$ man grep

… … ..

-i, –ignore-case
Ignore case distinctions in both the PATTERN and the input
files. (-i is specified by POSIX.)

… … …
$

Is that what you wanted?
$ grep -i PEAFOWL hosts
127.0.0.1 peafowl
$ grep -i peafowl hosts
127.0.0.1 peafowl

Reply

6 Mac October 5, 2012 at 3:59 pm

Thanks Thad I will check that out.

:)

Reply

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