4.3BSD - /usr/man/cat8/sticky.0

STICKY(8)                                                            STICKY(8)


NAME
       sticky - persistent text and append-only directories

DESCRIPTION
       The  sticky bit (file mode bit 01000, see chmod(2)) is used to indicate
       special treatment for certain executable files and directories.

STICKY TEXT EXECUTABLE FILES
       While the ‘sticky bit’ is set on a sharable executable file,  the  text
       of  that  file will not be removed from the system swap area.  Thus the
       file does not have to be fetched from the file system upon each  execu‐
       tion.   Shareable  text  segments  are  normally placed in a least-fre‐
       quently-used cache after use, and thus  the  ‘sticky  bit’  has  little
       effect on commonly-used text images.

       Sharable executable files are made by the -n and -z options of ld(1).

       Only  the  super-user  can  set the sticky bit on a sharable executable
       file.

STICKY DIRECTORIES
       A directory whose ‘sticky bit’ is set becomes an append-only directory,
       or,  more  accurately,  a  directory  in which the deletion of files is
       restricted.  A file in a  sticky  directory  may  only  be  removed  or
       renamed  by  a  user if the user has write permission for the directory
       and the user is the owner of the file, the owner of the  directory,  or
       the  super-user.   This feature is usefully applied to directories such
       as /tmp which must be publicly  writable  but  should  deny  users  the
       license to arbitrarily delete or rename each others’ files.

       Any user may create a sticky directory.  See chmod(1) for details about
       modifying file modes.

BUGS
       Since the text areas of sticky text executables are stashed in the swap
       area, abuse of the feature can cause a system to run out of swap.

       Neither  open(2)  nor  mkdir(2)  will create a file with the sticky bit
       set.


4th Berkeley Distribution        May 26, 1986                        STICKY(8)