Windows Services for UNIX (SFU) is a discontinued software package produced by Microsoft which provided a Unix environment on Windows NT and some of its immediate successor operating-systems. SFU 1.0 and 2.0 used the MKS Toolkit; starting with SFU 3.0, SFU included the Interix subsystem, which was acquired by Microsoft in 1999 from US-based Softway Systems as part of an asset acquisition. SFU 3.5 was the last release and was available as a free download from Microsoft. Windows Server 2003 R2 included most of the former SFU components (on Disk 2), naming the Interix subsystem component Subsystem for UNIX-based Applications (SUA). In Windows Server 2008 and high-end versions of both Windows Vista and Windows 7 (Enterprise and Ultimate), a minimal Interix SUA was included, but most of the other SFU utilities had to be downloaded separately from Microsoft's web site. The Interix subsystem included in SFU 3.0 and 3.5 and later released as SUA Windows components provided header files and libraries that made it easier to recompile or port Unix applications for use on Windows; they did not make Linux or other Unix binaries (BSD, Solaris, Xenix etc) compatible with Windows binaries. Like the Microsoft POSIX subsystem that Interix replaced, it is best thought of as a distinct Unix-like platform. It is replaced by Windows Subsystem for Linux in Windows 10 and Windows Server 2019. Components As of SFU 3.5, it contained: Over 350 Unix utilities such as vi, ksh, csh, ls, cat, awk, grep, kill, etc. GCC 3.3 compiler, includes and libraries (through an MS libc) A cc-like wrapper for Microsoft Visual Studio command-line C/C++ compiler GDB debugger Perl NFS server and client A pcnfsd daemon X11 tools and libraries Tools for making NFS mount-points appear as Windows shares, and vice versa (gateway services) A NIS server capability linked with Active Directory (AD) Some Windows/Unix authentication information-synchronization tools SFU did not contain the following: bash, OpenSSH, sudo, CVS, ClamAV, bzip2, gmake, curl, emacs, Apache, XView, Ruby, Tcl, Python Although SFU includes X Window System client libraries and applications, it does not contain a native X server. Administrators may configure any of the numerous third-party Windows X servers. Fully featured free options include Cygwin/X, Xming and WeirdX. Releases 1.0 Microsoft produced at least one beta release of the initial version of SFU before its final release in February 1999. This release, in English only, was supported on the Windows NT