Source : Free On-Line Dictionary of Computing

installable file system
     
         (IFS or "File System Driver", "FSD") An
        {API} that allows you to extend {OS/2} to access files stored
        on disk in formats other than {FAT} and {HPFS}, and access
        files that are stored on a {network file server}.
     
        For example an IFS could provide programs running under OS/2
        (including DOS and Windows programs) with access to files
        stored under {Unix} using the {Berkeley fast file system}.
     
        The other variety of IFS (a "remote file system" or
        "redirector") allows file sharing over a {LAN}, e.g. using
        Unix's {Network File System} {protocol}.  In this case, the
        IFS passes a program's file access requests to a remote file
        server, possibly also translating between different file
        attributes used by OS/2 and the remote system.
     
        Documentation on the IFS API has been available only by
        special request from IBM.
     
        An IFS is structured as an ordinary 16-bit {DLL} with entry
        points for opening, closing, reading, and writing files, the
        swapper, file locking, and {Universal Naming Convention}.  The
        main part of an IFS that runs in {ring} 0 is called by the
        OS/2 {kernel} in the context of the caller's process and
        {thread}.  The other part that runs in ring 3 is a utility
        library with entry points for FORMAT, RECOVER, SYS, and
        CHKDSK.
     
        {EDM/2 article (http://www.edm2.com/0103/)}.
     
        (1999-04-07)