


TFS(4S)          DEVICES AND NETWORK INTERFACES           TFS(4S)



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



Sun Release 4.1   Last change: 23 November 1988                 1






TFS(4S)          DEVICES AND NETWORK INTERFACES           TFS(4S)



     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), mount(2V), tfsd(8), mount_tfs(8)

















































Sun Release 4.1   Last change: 23 November 1988                 2



