"Whois" is a tool for querying information bases (called registries) regarding domain names and IP addresses. The data contained in these registries bears no guarantee, but may generally be used to find out who owns a domain name or a machine, particularly if a dispute arises.
Whois has two main purposes:
Command-line Whois tools are available for certain operating systems, including Unix (such as Linux or MacOS X), in which the command syntax is as follows:
whois domain_name_or_ip_addressThere are usually a large number of settings for this command, depending on the operating system. To learn what they are, simply enter:
whois --help
There are also online Whois lookup services for nearly all domain name extensions, most of which are accessible at http://whois.nic.extension, where extension stands for the final part of the domain name. A simple search for "whois" in a search engine also gives the addresses of websites that offer such services.
Administrative information regarding IP addresses are archived by the following organisations (source: IANA):