Windows Blue under the hood: MinKernel and BaseFS

Windows Blue under the hood: MinKernel and BaseFS

Summary: 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.


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, 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.

Topics: Windows, Tablets, PCs, Microsoft Surface, Windows 8, Windows Server


Mary Jo has covered the tech industry for 30 years for a variety of publications and Web sites, and is a frequent guest on radio, TV and podcasts, speaking about all things Microsoft-related. She is the author of Microsoft 2.0: How Microsoft plans to stay relevant in the post-Gates era (John Wiley & Sons, 2008).

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  • This is cool.

    I am waiting for more information about BaseFS and MinKernel implementation within Blue, it seems Microsoft is keeping its promise to unify the Windows Platform.
    Ram U
    • Windows Blue under the hood: MinKernel and BaseFS = Ford Model T Idea

      Blue will be a fail also..............end of story
      Over and Out
      • it will

        But less harder than other os..
      • hehe

        After blue, there probably will be red and green then 9 and so on. Doesn't matter if this fails though I don't see It failing as windows is going inexpensive 7-inch land.
  • It's great to see the modernization of Windows continue

    MinWin was a great first step. That was followed by a major re-organization of much of the rest of the OS for Win8.

    Now it looks as if Microsoft may have managed to pick apart some of the kernel subsystems, including the filesystem, into cleanly separated subsystems that will result in looser coupling and greater freedom and flexibility to support more device types, hardware architectures etc. moving forwards.

    The net result of this work is that t it's increasingly likely that the next couple of versions of Windows, WinPhone, Server and Xbox will share an increasingly common OS infrastructure and app platform allowing developers to write apps using more shared code and more similar user experience paradigms.

    In other words, all Windows users will benefit.
    • RE:

      And we know that everything that comes out of your brain is going to be some witless, obtuse comment; a canned response containing nothing but Microsoft praises. Why don't you pack it up and move to the MS TechNet forum where you fanbois can feed off of each others' brotherly love?
      • Umm ... I'm no MS fan, but nothing he said was wrong

        Just because you have a knee doesn't mean you have to be a jerk. Jus' sayin'.
      • Interesting.

        I tried to put a little context around this article. Sorry you took such offence to my observations.

        Care to add anything constructive?
        • hmmmm,....

          Can't spell either.
          • Sorry?

            What did I spell incorrectly?
          • File system technically is two words

            though your spelling is acceptable.

            Though I've never seen anyone follow a comma with four periods, as Big John has. ;)
            William Farrel
          • Since you asked

            Although I do *not* approve of meaningless flamewars and usually wouldn't participate, since you asked... you used "offence" where you actually meant "offense".
          • Incorrect Spelling

            Ah, but those Brits who spell their words by normally replacing American usage of "s" with a "c" would love your "correct" British spelling. But of course, who pays any attention to exclusively British mannerisms and spelling, other than the Europeans who pick up the same, "wrong" (in the view of Americans) British spellings.
          • Errrr weisgaber I think ......

            that the British and their spelling has been around for much longer than European settlement of the USA So maybe it is the American usage that is replacing THEIR letters??
          • Not set in stone

            At the time the US was founded the language was still highly variable in its written form. Not nearly as bad as a century earlier but there was still far to go on the formalization of spelling and usage. Things were still very much in flux when each nation formalized its version of English.
          • Just because it's interesting...

            The English of the middle ages were not too hung up on spelling...

            Check out William Tyndale's New Testament where the same word is sometimes spelled in several different ways on the same page... :)
          • Both spellings are correct

            I went to college in Hong Kong, and to this day I still write 'criticise' rather than 'criticize', though raised in the US. Cut the guy some slack. British spelling or American spelling, we still know what is meant, and should never take offence. :)
          • Cultural fascists like you

            Need to get out more
          • Not in the Queen's Enligh it's not

          • English even

            FOR GOD'S SAKE ZDNET ... WHEN are you going to restore the comment editing capability?