Microsoft Windows Services for UNIX (SFU) is a software package produced by Microsoft which provides a Unix subsystem and other parts of a full Unix environment on Windows NT and its successors. The subsystem included is called Interix.
Though both Cygwin (a free alternative to Interix) and Windows Services for Unix provide header files and libraries that make it easier to recompile or port Unix applications for use on Windows, they do not make Unix binaries compatible with Windows binaries.
The current version of SFU contains:
SFU does not contain the following (but binaries are available for a separate installation):
Although X Window System client libraries and applications are provided, SFU does not contain a native X server. Any of the numerous third-party Windows X servers can be used. Fully featured free alternatives include Cygwin/X, Xming, WeirdMind and WeirdX.SFU 3.5
This was the final release of SFU and the only release to be distributed free of charge. It was released January 2004 and included both English and Japanese versions for Windows 2000, Windows XP Professional, and Windows Server 2003 on x86 platforms with Internet Explorer 5.0+. It included Interix subsystem version 8.0 (release 3.5) adding internationalization support (at least for the English version which did not have such until now) and POSIX threading. This release could only be installed to an NTFS file system (earlier versions supported FAT; this was probably for new features in Interix 8.0). The following UNIX versions were supported: Solaris 7 and 8, Red Hat Linux 8.0, AIX 5L 5.2, and HP-UX 11i. It included the following components:
Windows Vista Enterprise and Ultimate Editions also contain the Services for Unix components, now called the Subsystem for UNIX-based applications (SUA), and Client for NFS v3. The utilities and SDK are required to be downloaded separately. However, the server components from the SFU product line (namely Server for NFS, User Name Mapping, Server for NIS, Password Synchronization etc) are not included.
Microsoft does not intend to produce any further standalone versions of the product. SFU will be available for download until 2009; general support will continue until 2011; extended support until 2014.
Character translation must be used to accommodate filenames with a colon (:) or other characters that are not compliant with Windows file systems. Files with the same name but different cases are also not allowed.
Interix is the name of an optional, full-featured POSIX and Unix environment subsystem for Microsoft's Windows NT-based operating systems. It is a component of the Services for Unix (SFU) release 3.0 and 3.5 (this last one is distributed free). The most recent releases of Interix, 5.2 and 6.0, are components of the Windows Server 2003 R2 and Windows Vista distributions with the moniker "SUA"  (Subsystem for Unix-based Applications).
Like the Microsoft POSIX subsystem in Windows NT, Interix is an implementation of an environment subsystem running atop the Windows kernel. Interix provides numerous open source utilities, much like the cygwin project.
The complete installation of Interix includes:
The development environment includes support for C, C++ and Fortran. Threading is supported using the Pthreads model. Additional languages can be obtained (Python, Ruby, Tcl, etc.). The pkgsrc software packaging/build system was ported to work with Interix 3.5, and may work with newer versions (not yet tested).
Starting with release 5.2 the following capabilities were added:
With release 6.0 the following new features can be expected:
Also Interix is slated to be included only with Vista Ultimate and Enterprise (not other Vista editions) from the next version onwards.
This product began to be developed in 1996 under the product name OpenNT by Softway Systems, Inc. before the name was changed to Interix in 1998. The last release by Softway Systems was release 2.2. Interix was acquired by Microsoft in 1999. Microsoft continued to distribute Interix 2.2 as a standalone product until 2002. Interix release 3.0 was released as component of Services for Unix (SFU) 3.0 in 2002. Interix release 3.5 was released as component of SFU 3.5 in January, 2004. Interix became integrated as component of the regular Windows OS distribution as a component of Windows 2003 Server R2 in December, 2005 at release 5.2 and is a component of the Windows Vista release as release 6.0 (RTM November, 2006). Windows Server 2008 also contains Interix under the SUA component name (released February 27, 2008).