# sunos TFS.4s

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    NAME
         tfs, TFS - translucent file service

    CONFIG
         optionsTFS

    SYNOPSIS
         #include <sys/mount.h>
         mount("tfs", dir, M NEWTYPE|flags, nfsargs);

    DESCRIPTION
         The translucent file service (TFS) supplies a  copy-on-write
         filesystem  allowing  users  to share file hierarchies while
         providing each user with  a  private  hierarchy  into  which
         files  are copied as they are modified.  Consequently, users
         are isolated from each other's changes.

         nfsargs specifies NFS style mount(2V)  arguments,  including
         the  address  of  the file server (the tfsd(8)) and the file
         handle to be mounted.  dir is the directory on which the TFS
         filesystem is to be mounted.

         TFS allows a user to mount a private, writable filesystem in
         front of any number of public, read-only filesystems in such
         a way that the contents of  the  public  filesystems  remain
         visible  behind the contents of the private filesystem.  Any
         change made to a file that is being  shared  from  a  public
         filesystem  will  cause  that  file  to  be  copied into the
         private filesystem, where  the  modification  will  be  per-
         formed.

         A directory in a TFS filesystem  consists  of  a  number  of
         stacked  directories.   The searchpath TFS uses to look up a
         file in a directory corresponds to the stacking  order:  the
         TFS  will  search  the "frontmost" directory first, then the
         directory behind it, and so on until the first occurrence of
         the file is found.  Modifications to a file can be made only
         in the frontmost  directory.   TFS  copies  a  file  to  the
         frontmost directory when the file is opened for writing with
         open(2V) or when its stat(2V) attributes are changed.

         If a user removes a file  which  is  not  in  the  frontmost
         directory,  TFS  creates  a  whiteout entry in the frontmost
         directory and leaves the file intact in the back  directory.
         This  whiteout entry makes it appear that the file no longer
         exists, although the file can be reinstated in the directory
         by  using  the  unwhiteout(1) command to remove the whiteout
         entry.  The lsw(1) command lists whiteout entries.

         TFS filesystems are served by the tfsd(8).  A TFS filesystem
         is  mounted  on  a  directory by making a TFS MOUNT protocol
         request of the tfsd, specifying the directories that are  to
         be stacked.  The tfsd responds with a file handle, which the
         client then supplies to the  mount(2V)  system  call,  along
         with the address of the tfsd.

    SEE ALSO
         lsw(1), unwhiteout(1),