You can use a 3rd party site or tool such as domainwhitepages.com or our registration site, o2link.com

You can also run "whois" command from an SSH command line like this:

whois yourdomain.com

If you want to look in whois record directly on the whois server at your registrar, you can use -h option to specify the whois server.

For example:
whois -h whois.internic.net o2link.com