For years one of the few truly irreplaceable Microsoft technologies has been Active Directory. Now it's that much closer to being replaced, by the open source Samba project in its fourth major revision.

Samba's the open source implementation of Microsoft's SMB protocol, one of the many proprietary creations it was forced to more thoroughly document as a sign of its increasing willingness to play fair with its competitors. It's normally been used to allow Linux clients to talk to Windows servers, whether actual servers or just Vista / XP fileshares.

For a long time Samba was a bit of a problem child -- difficult to configure, but also spotty in its support for different iterations of SMB (e.g., Vista shares vs. XP shares). Samba 4 promises to fix all that -- to "just work" out of the box, and to implement a great many things that previously required a Windows server. Another key feature, support for Group Policy on Windows clients, ought to make it that much easier to administer Windows machines from Linux boxes.

How this will work out in the field is another story -- i.e., whether it'll be possible to replace Windows AD servers with Linux boxes one-for-one. It doesn't help Microsoft that they just announced a massive 5,000-man layoff over the next 18 months and gave a gloomy forecast for the 2nd half of 2009, though. If there's suddenly that much less of a reason to use a Windows server, Microsoft had better think about what they can do to make up the difference.

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