Whois is a protocol which runs on port no. 43 and it is also act as query. Whois helps to get the information regarding internet resources like domain name and IP Address network blocks.
Mostly it is widely used for getting information about domain like owner of domain name,its registrar,Date of expiry etc.

Install whois on CentOS 8 and RHEL 8

To install whois in CentOS 8 or RHEL 8 use the given below command.

sudo dnf install whois

Given below is the output of installing whois in our system.

[sharad@localhost ~]$ sudo dnf install whois
CentOS-8 - AppStream                                                                            260 kB/s | 5.8 MB     00:22    
CentOS-8 - Base                                                                                  26 kB/s | 2.2 MB     01:27    
CentOS-8 - Extras                                                                               1.8 kB/s | 6.7 kB     00:03    
Dependencies resolved.
================================================================================================================================
 Package                       Arch                       Version                           Repository                     Size
================================================================================================================================
Installing:
 whois                         x86_64                     5.5.1-2.el8                       AppStream                      78 k
Installing dependencies:
 whois-nls                     noarch                     5.5.1-2.el8                       AppStream                      38 k

Transaction Summary
================================================================================================================================
Install  2 Packages

Total download size: 116 k
Installed size: 341 k
Is this ok [y/N]: y
Downloading Packages:
(1/2): whois-nls-5.5.1-2.el8.noarch.rpm                                                          17 kB/s |  38 kB     00:02    
(2/2): whois-5.5.1-2.el8.x86_64.rpm                                                             9.1 kB/s |  78 kB     00:08    
--------------------------------------------------------------------------------------------------------------------------------
Total                                                                                            12 kB/s | 116 kB     00:09     
warning: /var/cache/dnf/AppStream-fd636d66ef3d60cc/packages/whois-5.5.1-2.el8.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 8483c65d: NOKEY
CentOS-8 - AppStream                                                                            321 kB/s | 1.6 kB     00:00    
Importing GPG key 0x8483C65D:
 Userid     : "CentOS (CentOS Official Signing Key) "
 Fingerprint: 99DB 70FA E1D7 CE22 7FB6 4882 05B5 55B3 8483 C65D
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
Is this ok [y/N]: y
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                        1/1 
  Installing       : whois-nls-5.5.1-2.el8.noarch                                                                           1/2 
  Installing       : whois-5.5.1-2.el8.x86_64                                                                               2/2 
  Running scriptlet: whois-5.5.1-2.el8.x86_64                                                                               2/2 
  Verifying        : whois-5.5.1-2.el8.x86_64                                                                               1/2 
  Verifying        : whois-nls-5.5.1-2.el8.noarch                                                                           2/2 

Installed:
  whois-5.5.1-2.el8.x86_64                                     whois-nls-5.5.1-2.el8.noarch                                    

Complete!
[sharad@localhost ~]$ 

Now you can use the whois command in system

whois domainname eg. whois example.com
whois ip-address eg. whois 93.184.216.119

Note: Port no. 43 should be opened for connecting to whois database.

Install whois on CentOS 7/6 and Red Hat 7/6

In CentOS 7/6 and RHEL 7/6 , we will install the jwhois package which will provide the whois command.

sudo yum install jwhois

Know about whois: http://en.wikipedia.org/wiki/Whois