Goal: Highly interoperable Binary compatible FreeBSD, HP-UX, IBCS2, Linux, OSF/1, SVR4, SunOS, Ultrix, Win32 Source compatibility POSIX.1, POSIX.2, XPG/SUS (Single Unix Specification), BSD File systems FFS, ISO CD9660, EXT2FS, MS-DOS (FAT), AmigaDOS, NTFS Networking TCP/IP (including IPv6), AppleTalk, SMB (CIFS)