Five Things to Know About Longhorn Server Core

I’ve written about Server Core before -- in my Longhorn Server review of Beta Version 2. It's Microsoft’s great new addition to the Longhorn Server product. Essentially, Server Core is a slimmed-down, appliancelike version of Longhorn Server that functions in a couple of limited roles and does nothing else.

Server Core, as I see it, has three main advantages: it’s extremely focused, which means it does what it does very well, resulting in better performance, resilience and robustness than a full-fledged operating system. It also has limited dependencies on other pieces of the Windows puzzle, in that the Core is designed to work without a lot of other software installed; it can generally work by itself. In comparison, many of the previous Windows components aren’t really necessary -- like Windows Explorer or Internet Explorer, for example -- which is something that can’t be said for Windows Server 2003.

All of this translates into a far smaller attack surface than the standard Windows Server product, given all of the material that's been stripped out.

But there are some aspects of Server Core with which you might not yet be familiar, as well as some interesting facts and limitations of the "core"-based approach to computing. I’ll take a look at them here.

Server Core has no graphical user interface

This is probably the most unsettling but, upon reflection, most interesting and welcome difference with Server Core over the traditional Windows server operating system. When you boot Server Core, you’ll get a colored screen that looks like a single-color desktop, which might fool you into thinking that you installed the wrong version. But you’ll quickly be corrected as you get a command-prompt window that appears and then all activity stops. It looks a lot like regular Windows if you open Task Manager and kill the explorer.exe process.

Indeed, you can open Notepad -- just about the only graphical application installed -- but you can open it only from the command line, and you can’t save as another file; there is no support for displaying those sorts of Explorer windows. Essentially, you’ll need to think back to your DOS days to get accustomed to administering Server Core. The command line is very, very powerful -- in many instances you can accomplish more with commands, options and switches than you can with the GUI -- but it can be intimidating to start.

Server Core, while great, has limited scenarios in which it can be deployed

At the most fundamental level, Server Core can only be a file server, domain controller, DHCP server or DNS server. It can participate in clusters and network load-balancing groups, run the subsystem for Unix applications, perform backups using Server Core's improved capabilities, and be managed and report status through SNMP. There are a few other ancillary capabilities, but it’s pretty stripped down and only appropriate at this point for the four basic roles I just delineated. Future releases might expand the roles in which core-based operating systems can run, but this is not available yet.

You can’t run managed code -- that is, applications that require the .Net Framework

The code behind the .Net Framework is not modular enough to be broken up into just the components that Server Core will be able to run. (This might be added in future releases and looks to be reasonably high on the priority list.)

Not only does this mean you can’t run any custom Web applications you might have created, but you also lose access to some of the better management software that comes along with this generation of Windows, including Windows PowerShell (which used to go by the code name Monad). Server Core just isn’t a .Net machine at this point, so for Web applications and other custom software, you will need to deploy the regular, fully fleshed-out Longhorn Server edition of the operating system.

The most novel way to manage Server Core machines is through WS-Management

The new client operating system, Windows Vista, includes a great tool called Windows Remote Shell, or WinRS, that looks like it was made for administering Server Core machines. Through the WS-Management standard, clients running WinRS software can pipe a command to a Server Core machine and have it executed with no problem. But there is a limitation. As of Longhorn Server Beta 2, WinRS couldn’t really handle interaction, so commands had to be completely encapsulated into one transmission to be successfully executed. However, this may change as development on Longhorn Server continues and with the official release of Windows Vista later this month.

Third-party software designed to be installed on the Server Core machine may not work properly

Mainly, you are going to encounter problems with software that is designed to display widgets in the system tray, like some antivirus and shell modification applications. You may also encounter some problems with management software, although typically these types of applications work in the background and don’t display anything graphically.

Lastly, driver installation will be a sore point in a few instances, and you’ll need to either use hardware with drivers bundled with the Server Core release or preload the appropriate drivers with the included Drvload utility. You might face driver signing issues as well, though these can be mitigated by actually touching the driver-signing policy on the Server Core machine through Group Policy -- but of course, you have to do that remotely.

Jonathan Hassell is an author, consultant and speaker on a variety of IT topics. His published works include RADIUS, Hardening Windows, Using Windows Small Business Server 2003 and Learning Windows Server 2003. His work appears regularly in such periodicals as Windows IT Pro magazine, PC Pro and TechNet Magazine. He also speaks worldwide on topics ranging from networking and security to Windows administration. He is currently an editor for Apress Inc., a publishing company specializing in books for programmers and IT professionals.

Copyright © 2007 IDG Communications, Inc.

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