Microsoft have released a new build of Windows 10 Server for Windows Insiders. Build 16267 of the server OS is available for testing from Microsoft with the following activation codes:

  • Windows Server Datacenter Core: B69WH-PRNHK-BXVK3-P9XF7-XD84W
  • Windows Server Standard Core: V6N4W-86M3X-J77X3-JF6XW-D9PRV

There are no new features with this build just bug fixes:

General Scenario Highlights

Developers and Containers:

New base container images (available on Windows Insider Docker Hub repo)

Optimized Nano Server base image (over 70% smaller)

The .NET team is providing a preview image based on Nano Server with .NET Core 2.0

The PowerShell team is providing a preview image based on PowerShell 6.0

Optimized Server Core base image (over 20% smaller)

Support for SMB volume mounting

Infrastructure for Orchestrators

Networking enhancements for ongoing Kubernetes work

Named pipe mapping support

Bug fixes, performance enhancements

Cloud Guest:


TLS info: administrators can make specific recommendations to default to HTTPS

Disaster Recovery

Storage Replica Test Failover

Guest + Host better together

vPMEM in Guest: Tenants can use and manage PMEM/SCM

Tenant-Aware VM Start Ordering: App Ready / OS Heartbeat for better load balancing

Guest RDMA

Improvement in time accuracy

Azure enlightened clusters – optimized to run on Azure IaaS

Cloud Host:

Software Defined Data Center (SDDC) host


Shielded Linux VM

SDN: Encrypted virtual networks

Secure clusters

SMB 1 disabled by default

Resiliency and Availability

SDN: Reduced downtime for tenant connections through gateways

Spaces Direct: Scoped Spaces to mitigate impact of multi-node loss

Spaces Direct: Marginal drive handling for predictive detection of drive failures


Data Deduplication available for ReFS

New Data Deduplication DataPort API for optimized ingress/egress

Space efficiency with ReFS Compaction

Performant Spaces Direct Multi Resilient Volumes (MRV)

Hyper-converged Scale

Cluster Sets: Significantly increases hyper-converged SDDC cloud scale by grouping multiple clusters into a larger fabric

Hardware support

Support for Storage Class Memory (SCM) in Spaces Direct

What’s New in Build 16257 for Windows Server

Windows Subsystem for Linux (WSL) is available on Windows Server

Windows Subsystem for Linux (WSL) is now available on Windows Server along with a compliment of Linux distributions.

Test WSL on Windows Server.  WSL runs unmodified Linux (ELF64) binaries natively.  With the additions of WSL you can run node.js, Ruby, Python, Perl, Bash scripts or other tools that expect Linux behaviors, environment, or filesystem-layout, the ability to install and run Linux with WSL expands the tools at your disposal on Windows Server.

At this time, WSL does not support persistent Linux services (such as daemons and jobs) as background tasks. To enable WSL and install a Linux distribution, see Enable the Windows Subsystem for Linux and Install a Linux distribution in the Windows Server 2016 Installation Guide on GitHub.

Read more in this blog or follow the installation guide to try it out.

How to Download

The latest Windows Server build and matching symbols are available for download here. Matching Windows Server container images will be available via the Docker Hub. For more information about Windows Server containers and Insider builds, please visit

The following keys are available for unlimited activations of Windows Server. These keys may be used throughout the pre-release cycle.

Server Datacenter Core: B69WH-PRNHK-BXVK3-P9XF7-XD84W

Server Standard Core: V6N4W-86M3X-J77X3-JF6XW-D9PRV

NOTE: If you signed up for Windows Insiders for Business using an AAD account, there is a temporary issue with access to the Windows Server Download page using AAD accounts. If you registered using an MSA account at the Windows Insider program, your MSA account may be used to access the page and to download builds until this is resolved.

It’s all about your feedback!

Use the Feedback Hub app to provide feedback on Windows Server builds. Feedback Hub comes pre-installed on Windows 10. Register a Windows 10 device with the Windows Insider or Windows Insider for Business programs. Open the Feedback Hub application. Choose the Server category and then the appropriate subcategory for your feedback. Please indicate what edition and build number you are providing feedback on. The Feedback Hub app cannot scan a server for diagnostic information, however you may manually attach screenshots or other files to your feedback entry.

We encourage you to visit the Windows Server Insiders space on the Microsoft Tech Communities forum to collaborate, share and learn from experts.

The expiration date for this server preview build is 12/4/2017.

Known issues

The background tasks infrastructure service (Bisrv.dll) may cause a system crash because of a null class pointer read error (0xC0000005) or a failfast corrupt list entry (0xC0000409) during a Distributed Component Object Model (DCOM) launch, or because of a critical process bug check (error code 0xC0000409, bug check 0xEF) in the host process for Windows services (Svchost.exe).

Calling into the firewall service may hang: Apps that call into the firewall, such apps that use networking, may become unresponsive until the user reboots because of an application hang end-task error (0xCFFFFFFF) in the Windows firewall API library (FirewallAPI.dll), which occurs when the library is blocked on an advanced local procedure call (ALPC) port while attempting to diagnose a connection failure and retrieve information.

Cluster Sets: A couple of key functionalities to enable end-to-end testing of Cluster Sets scenarios are not present in this build, so defer all evaluation of this scenario to a future build.

Bugcheck during volume creation: A stop error may occur during volume creation in a cluster. The recommended workaround is, after restarting the computer, to delete the volume and try creation again.

Bugcheck during volume repair: A stop error may occur during volume repair in a cluster. The recommended workaround is to restart the computer. No corruption or data loss is expected.

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