Windows Blue under the hood: MinKernel and BaseFS

Since rumors about Windows Blue first surfaced, there's been talk that the Windows 8 update would include more than just UI tweaks. Clues about some of these deeper level changes are emerging.
Written by Mary Jo Foley, Senior Contributing Editor

With the recently leaked Windows Blue build out for the past few days, those downloading it are continuing to find new details as they dissect the code.

While some of the early user-interface changes -- in some cases, making Windows Blue look and feel more like Windows Phone -- have been a big focus, the under-the-hood changes have gotten less coverage.


But over on ITWorld.com, long-time Microsoft watcher Sandro Villinger has shared a few of his findings.

Villinger found mention of something called "BaseFS" buried in the Windows Blue code. This doesn't seem to be a new name for ReFS, the new file system for Windows 8 and Windows Server 2012. Instead, according to one of my contacts, BaseFS is more of an internal concept that has to do with shared functionality between the different file systems

Interesting. Even more interesting (to me, at least) is Villinger's find regarding "Minkernel." (A screen capture by Villinger showing references in Windows Blue to BaseFS and Minkernel is embedded above in this post.)

Microsoft has been working to detangle the Windows hairball since it was developing Windows Vista, and possibly before. MinWin is the Windows "core" that resulted. MinWin includes some kernel interfaces, but it isn't simply the Windows kernel. As I've described it in the past, MinWin is the heart of Windows, organized in a way so that none of the included parts has any dependencies on anything outside of MinWin.

So what is MinKernel in this context? According to one of my sources, MinKernel is a minimal set of functionality that is shared across the different Windows kernels that run on x86, ARM, Windows Phone and Xbox. MinKernel is the one base-level implementation on top of which these platforms are built, the same way that BaseFS may be the base-level file system that is common across different platforms.

Update: WalkingCat (@h0x0d on Twitter) found MinKernel references dating back to Windows 7. He pointed me to an NVLabs security-research presentation mentioning it, a slide from which is here:


Since word of Windows Blue first surfaced months ago, tipsters have said there would be kernel-level and driver-level changes included as part of this first operating-system update to Windows 8.

Villinger also found a few more Blue clues worth noting. He discovered some references within the Blue bits to a Modern/Windows Store version of the Windows Defender antivirus app that Microsoft bundled with Windows 8 and Windows RT. (Right now, Defender is a Desktop, not a Metro-Style app.) He also found some hints that indicate that 3G/4G tethering support may be built into Blue.

My ZDNet colleague Ed Bott also discovered a change in Microsoft's certification guidelines for Windows 8 hardware that clear the path for 7- and 8-inch tablets.

Microsoft officials have been hinting for the past couple months that smaller Windows 8 tablets were likely in the pipeline. Rumors of both a 7-inch HTC Windows tablet and an Xbox Surface media-consumption tablet are out there.

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