Query domain information with RDAP
At Your Fingertips
RDAP provides structured information about domains. Besides practical command-line query tools, there are also libraries for integrating the protocol into your own programs.
Since the early days of the Internet and its division into different organizational areas, users have needed a way to obtain information about domains, the IP addresses they use, their owners, and a way of mapping them to each other. The WHOIS protocol was devised for this purpose in 1982 and introduced in RFC 812 [1]. The service can be accessed using a command-line tool of the same name, whois
. The age and importance of the protocol are evident from, among other things, its very low number – 43 – in the list of standardized ports for network services [2], which can be found in the file /etc/services
[3].
Thus far, this plain-text protocol has proven its value thanks to its simplicity, even if only request and response have been standardized in a fairly rough framework. The last update in RFC 3912 dates back to 2004 [4]. (See the "Regulations on WHOIS in Europe" box for details on that topic.) The search for a replacement has been underway for some time. The ideal candidate is the Registration Data Access Protocol (RDAP) [6], which is defined in more detail in RFC 9082 [7].
RDAP
The idea is for RDAP to completely replace WHOIS. It provides information about a domain via the HTTP protocol. This eliminates the need to open port 43 in the firewall. RDAP was standardized back in 2015 by an Internet Engineering Task Force (IETF) working group.
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.

News
-
System76 Releases COSMIC Alpha 7
With scores of bug fixes and a really cool workspaces feature, COSMIC is looking to soon migrate from alpha to beta.
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.
-
What Open Source Pros Look for in a Job Role
Learn what professionals in technical and non-technical roles say is most important when seeking a new position.
-
Asahi Linux Runs into Issues with M4 Support
Due to Apple Silicon changes, the Asahi Linux project is at odds with adding support for the M4 chips.
-
Plasma 6.3.4 Now Available
Although not a major release, Plasma 6.3.4 does fix some bugs and offer a subtle change for the Plasma sidebar.
-
Linux Kernel 6.15 First Release Candidate Now Available
Linux Torvalds has announced that the release candidate for the final release of the Linux 6.15 series is now available.
-
Akamai Will Host kernel.org
The organization dedicated to cloud-based solutions has agreed to host kernel.org to deliver long-term stability for the development team.