WHOIS is a TCP-based query and response protocol that is commonly used to provide information services to Internet users. It returns information about the registered Domain Names, an IP address block, Name Servers and a much wider range of information services.

In Linux, the whois command line utility is a WHOIS client for communicating with the WHOIS server (or database host) which listen to requests on the well-known port number 43, which stores and delivers database content in a human-readable format.

Read Also: 10 Linux Dig (Domain Information Groper) Commands to Query DNS

whois command line utility does not come pre-installed on many Linux distributions, run the appropriate command below for your distribution to install it.

# yum install whois		#RHEL/CentOS
# dnf install whois		#Fedora 22+
$ sudo apt install whois	#Debian/Ubuntu

How to Find IP Address Information

To get the information about specific IP Address issue the command as shown in the below example.

$ whois 216.58.206.46

#
# ARIN WHOIS data and services are subject to the Terms of Use
# available at: https://www.arin.net/whois_tou.html
#
# If you see inaccuracies in the results, please report at
# https://www.arin.net/public/whoisinaccuracy/index.xhtml
#


#
# The following results may also be obtained via:
# https://whois.arin.net/rest/nets;q=216.58.206.46?showDetails=true&showARIN=false&showNonArinTopLevelNet=false&ext=netref2
#

NetRange: 216.58.192.0 - 216.58.223.255
CIDR: 216.58.192.0/19
NetName: GOOGLE
NetHandle: NET-216-58-192-0-1
Parent: NET216 (NET-216-0-0-0-0)
NetType: Direct Allocation
OriginAS: AS15169
Organization: Google LLC (GOGL)
RegDate: 2012-01-27
Updated: 2012-01-27
Ref: https://whois.arin.net/rest/net/NET-216-58-192-0-1



OrgName: Google LLC
OrgId: GOGL
Address: 1600 Amphitheatre Parkway
City: Mountain View
StateProv: CA
PostalCode: 94043
Country: US
RegDate: 2000-03-30
Updated: 2017-12-21
Ref: https://whois.arin.net/rest/org/GOGL
...

How to Find Domain Information

To get the information about the registered domain, simply issue the following command with the domain name. It will retrieve domain data including availability, ownership, creation, expiration details, name servers, etc.

$ whois google.com

Domain Name: GOOGLE.COM
 Registry Domain ID: 2138514_DOMAIN_COM-VRSN
 Registrar WHOIS Server: whois.markmonitor.com
 Registrar URL: http://www.markmonitor.com
 Updated Date: 2011-07-20T16:55:31Z
 Creation Date: 1997-09-15T04:00:00Z
 Registry Expiry Date: 2020-09-14T04:00:00Z
 Registrar: MarkMonitor Inc.
 Registrar IANA ID: 292
 Registrar Abuse Contact Email: [email protected]
 Registrar Abuse Contact Phone: +1.2083895740
 Domain Status: clientDeleteProhibited https://icann.org/epp#clientDeleteProhibited
 Domain Status: clientTransferProhibited https://icann.org/epp#clientTransferProhibited
 Domain Status: clientUpdateProhibited https://icann.org/epp#clientUpdateProhibited
 Domain Status: serverDeleteProhibited https://icann.org/epp#serverDeleteProhibited
 Domain Status: serverTransferProhibited https://icann.org/epp#serverTransferProhibited
 Domain Status: serverUpdateProhibited https://icann.org/epp#serverUpdateProhibited
 Name Server: NS1.GOOGLE.COM
 Name Server: NS2.GOOGLE.COM
 Name Server: NS3.GOOGLE.COM
 Name Server: NS4.GOOGLE.COM
....

The formatting of information will differ based on the WHOIS server used. In addition, one downside of WHOIS is the lack of full access to the data, therefore check out these useful guides for querying DNS information in Linux:

1. Useful ‘host’ Command Examples for Querying DNS Lookups
2. 8 Linux Nslookup Commands to Troubleshoot DNS (Domain Name Server)

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