What’s different about Server Core in Windows Server 2019?

Microsoft made two changes to the Server Core installation option in Windows Server 2019: a smaller container image footprint and an optional application compatibility extension to Features on Demand (FoD).
Latest posts by Timothy Warner (see all)

One excellent side effect of the "PowerShell revolution," by which I mean Windows systems administrators now understand that knowing PowerShell is mandatory, is that these admins are more comfortable with command-line administration.

At the conferences and user groups I participate in, it pleases me to no end to hear working systems administrators tell me that Server Core is the only installation option they consider for Windows Server 2016 and Windows Server 2012 R2.

Microsoft plans to release Windows Server 2019 sometime during Q3 or Q4 2018. Meanwhile, I downloaded the latest Insider Preview build (17744, Long-Term Servicing Channel, or LTSC) to see what's new and what changed with the Server Core installation option.

As you can see in the next screenshot, the operating system installation gives you the same two options that we know and love from Windows Server 2016 and Windows Server 2012 R2:

Choose Server Core as your preferred installation option

Choose Server Core as your preferred installation option

Likewise, the sconfig.cmd utility appears unchanged in the Windows Server 2019 Preview, as shown in the following screenshot:

Use sconfig to configure the server locally

Use sconfig to configure the server locally

Okay, enough with the preliminaries! Let's get to what's new and what changed in Server Core in Windows Server 2019.

Server Core App Compatibility Feature-on-Demand (FoD) ^

FoD is a Windows Server feature with which you can offload server roles and features you don't need from your online or offline server image. Doing so not only reduces the Server Core hard disk footprint, but also decreases the server's potential attack surfaces because potentially vulnerable binaries are not available on the local file system.

Microsoft makes available an ISO optical disc image that contains several application compatibility updates to make working with Server Core easier. Of course, workload compatibility planning is top-of-mind for IT managers who plan to transition their GUI-enabled Windows Server VMs to Server Core; this FoD package set aims to make the transition a bit smoother.

After downloading the ISO and making its contents available to your Server Core VM, run the following DISM statement from an elevated command prompt or PowerShell session to install the app'sompatibility features (a restart is required):

Installing the App Cpatibility FoD packages

Installing the App Cpatibility FoD packages

Once you're back from that reboot, you can RDP into your Server Core box and run utilities like Microsoft Management Console (MMC) and SQL Server Management Studio (SSIS) if,cessaryI show you this in the nextreenshot:

Running some GUI apps in Server Core

Running some GUI apps in Server Core

Naturally, some of you may think, "Doesn't running GUI apps locally in Server Core defeat surpose?" My response is, basically, yes, but with the following two caveats:

Some of these App Compatibility updates may help you run server-side code on Server Core that you otherwise couldn't.his capability helps businesses more gradually and smoothly transition from a GUI server to a "headless" server environment.ou can look at this App Compatibility FoD optional update as a waypoint between the Minimal Server Interface GUI option and the full-on Server Core option.

Reduced Server Core Container Image Size ^

You remember Nano Server in Windows Server 2016? This ultra-slim Windows Server operating system is available in Windows Server 2019 only as a Docker container image.

Likewise, Server Core is available in Microsoft's Docker Hub repository as a container image, and the development team continues to whittle the image down to size. According to Microsoft, their objective is to reduce the Server Core base container image to approximately 2 GB. This means you can download the image much faster, ereby streamliningerformance.

After you install the Containers feature and Docker binaries on your Windows Server host, you can pull images directly from Docker Hub. The upcomingscreenshot shows the size comparison between the Windows Server 2016 Windows Server Core image and the Windows Server 2019 Windows Server Core Insider image:

Server Core image size comparison

Server Core image size comparison

Note that the Windows Server 2019 container image is 3.47 GB, compared to 10.9 GB for the Windows Server 2016 image.

New Management Option ^

You are likely more than accustomed to using the Remote Server Administration Tools (RSAT) in Windows Client to manage your Server Core instances. That rule remains valid for Windows Server 2019.

The new wrinkle, of course, is that now we have the Windows Admin Center,rmerly called "Project Honolulu. installed Preview build 1808 on my Windows 10 workstation and was able to interact flawlessly with my Windows Server 2019 Server Core host.

Windows Admin Center is not (yet) intended as a replacement forhe RSAT tools or Windows Remote Management (WinRM) remoting with PowerShell. However, this lightweight web application represents an auspicious start to centralized Windows Server management.

Managing firewall rules remotely with Windows Admin Center

Managing firewall rules remotely with Windows Admin Center

Wrap ^

In summary, we find that Server Core in Windows Server 2019 offers a more gradual transition path for admins hesitant to give up the GUI option, as well as streamlined Docker container image option.

I hope that you plan to transition all your Windows Server VMs to Server Core. You owe it to yourself to make your servers as performant, secure and easy to manage as possible.

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