SearchSystemsChannel.com: Do my customers need to buy a license to run XenServer?
Sander van Vugt: Yes, your customers do need a license to run XenServer, but as of version 5.5, this license is available for free. You can request this free license from Citrix's website.
SSC: If the XenServer license is free, why do customers need to get a license at all?
Van Vugt: That's just a matter of regulation. When your customer starts using the Citrix software, they'll need a legal agreement that makes it clear what they can and cannot expect from the software. This is normal practice for all software, even software that is available as open source or freeware.
SSC: Is Citrix Essentials available for free also?
Van Vugt: Citrix Essentials is an enterprise management product that exists for Citrix XenServer as well as Microsoft Hyper-V environments. Using Citrix Essentials, solutions providers can add high-availability features into a customer's environment. Citrix Essentials is not free; customers have to buy a per-server license to use it.
SSC: Is there a special license available for Citrix Essentials evaluation?
Van Vugt: Yes, there is. Thirty-day evaluation licenses are available to anyone at no cost, and there are no special requirements. All you have to do is apply for it online.
SSC: When a 30-day Citrix Essentials demo license expires, does that make my customers' environments unusable?
Van Vugt: The Citrix products in your customers' environments need a valid license to be operational. That means that the functionality of the XenServer will be temporarily broken. There is an easy solution for this -- just apply for a new 30-day demo license online. You'll get a new license for free, and you can continue testing the Citrix environment. If, however, you want to take the environment into production, you'll need to buy valid licenses. The Citrix environment will work with the demo licenses, but apart from being noncompliant, you'll take a major risk. The environment that your organization depends on may stop working without warning.
SSC: Registering licenses in Citrix XenCenter is often easy if an environment is not very big. What if there are multiple Xen domains, each with their own Xen environment? Does Citrix have something that makes license management easier for such an environment?
Van Vugt: For bigger environments, Citrix provides the Citrix License Server. This product integrates very well with products like Citrix XenApp or Citrix Provisioning Server. There is no good integration with XenServer yet, though. That means that in XenCenter, solutions providers can't use the Citrix License Server to manage licenses for currently installed XenServer hosts. Some of the products that are in Citrix Essentials do also integrate with the Citrix licensing platform. If you are using Citrix Provisioning Server, for example, you can manage licenses for that product through the Citrix licensing platform. To manage licenses of multiple XenServer hosts, you are bound to the options that are offered via the XenCenter interface.
SSC: If I don't use the Citrix License Server, how easy is it to display current license information for XenServer hosts?
Van Vugt: It's quite easy actually. Just select the XenServer host from XenCenter, and on the General tab you will find all license details that apply to your customer's server.
SSC: Do I have to set up a Citrix License Server?
Van Vugt: For pure XenServer environments, you don't have to use the Citrix License Server. Some other products that are part of Citrix Essentials do require the license server. Therefore, if your customers are starting to work with Citrix Essentials a lot, I would recommend installing a Citrix License Server for them.
SSC: What are the requirements to run Citrix License Server?
Van Vugt: Solutions providers need a current version of Windows Server -- anything from 2003 on will do. They'll also have to set up a Microsoft SQL database on that server. Microsoft provides a free version of SQL [Server] for that purpose that will fill all of your customer's needs.
About the expert
Sander van Vugt is an independent trainer and consultant living in the Netherlands. Van Vugt is an expert in Linux high availability, virtualization and performance and has completed several projects that implement all three. He is also the writer of various Linux-related books, such as Beginning the Linux Command Line, Beginning Ubuntu Server Administration and Pro Ubuntu Server Administration.
This was first published in June 2010