[unix-history] / usr / src / share / man / man8 / sticky.8

.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)sticky.8	8.1 (Berkeley) %G%
.\"
.Dd 
.Dt STICKY 8
.Os BSD 4
.Sh NAME
.Nm sticky
.Nd sticky text and append-only directories
.Sh DESCRIPTION
A special file mode, called the
.Em sticky bit
(mode S_ISVTX),
is used to indicate special treatment
for shareable executable files and directories.
See
.Xr chmod 2
or
the file
.Pa /usr/include/sys/stat.h
for an explanation of file modes.
.Sh STICKY TEXT EXECUTABLE FILES
An executable shareable file whose sticky bit is set
will not be immediately discarded from swap space after execution.
The kernel will hoard the text segment of the file for future
reuse and avoid having to reload the program.
Shareable text segments are normally placed
in a least-frequently-used cache after use,
and thus the `sticky bit' has little effect on commonly-used text images.
.Pp
Sharable executable files are created with the
.Fl n
and
.Fl z
options of
the loader
.Xr ld 1 .
.Pp
Only the super-user can set the sticky bit
on a sharable executable file.
.Sh 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
.Pa /tmp
which must be publicly writable but
should deny users the license to arbitrarily
delete or rename each others' files.
.Pp
Any user may create a sticky directory.
See
.Xr chmod 1
for details about modifying file modes.
.Sh 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.
.Pp
Neither
.Xr open 2
nor
.Xr mkdir 2
will create a file with the sticky bit set.
.Sh HISTORY
A
.Nm
command appeared in Version 32V AT&T UNIX.
Commit	Line	Data
7b766c04 KB	1	.\" Copyright (c) 1980, 1991, 1993
7b766c04 KB	2	.\" The Regents of the University of California. All rights reserved.
3c389526	3	.\"
b42074ab	4	.\" %sccs.include.redist.man%
3c389526	5	.\"
7b766c04	6	.\" @(#)sticky.8 8.1 (Berkeley) %G%
b42074ab CL	7	.\"
	8	.Dd
	9	.Dt STICKY 8
	10	.Os BSD 4
	11	.Sh NAME
	12	.Nm sticky
	13	.Nd sticky text and append-only directories
	14	.Sh DESCRIPTION
	15	A special file mode, called the
	16	.Em sticky bit
	17	(mode S_ISVTX),
87150da0	18	is used to indicate special treatment
b42074ab CL	19	for shareable executable files and directories.
	20	See
	21	.Xr chmod 2
	22	or
	23	the file
	24	.Pa /usr/include/sys/stat.h
	25	for an explanation of file modes.
	26	.Sh STICKY TEXT EXECUTABLE FILES
	27	An executable shareable file whose sticky bit is set
	28	will not be immediately discarded from swap space after execution.
	29	The kernel will hoard the text segment of the file for future
	30	reuse and avoid having to reload the program.
7cb6b840 MK	31	Shareable text segments are normally placed
	32	in a least-frequently-used cache after use,
	33	and thus the `sticky bit' has little effect on commonly-used text images.
b42074ab CL	34	.Pp
	35	Sharable executable files are created with the
	36	.Fl n
3c389526	37	and
b42074ab	38	.Fl z
3c389526	39	options of
b42074ab CL	40	the loader
	41	.Xr ld 1 .
	42	.Pp
87150da0 DS	43	Only the super-user can set the sticky bit
87150da0 DS	44	on a sharable executable file.
b42074ab	45	.Sh STICKY DIRECTORIES
87150da0 DS	46	A directory whose `sticky bit' is set
	47	becomes an append-only directory, or, more accurately,
	48	a directory in which the deletion of files is restricted.
	49	A file in a sticky directory may only be removed or renamed
	50	by a user if the user has write permission for the directory and
	51	the user is the owner of the file, the owner of the directory,
	52	or the super-user.
b42074ab CL	53	This feature is usefully applied to directories such as
b42074ab CL	54	.Pa /tmp
87150da0 DS	55	which must be publicly writable but
	56	should deny users the license to arbitrarily
	57	delete or rename each others' files.
b42074ab	58	.Pp
87150da0 DS	59	Any user may create a sticky directory.
87150da0 DS	60	See
b42074ab	61	.Xr chmod 1
87150da0	62	for details about modifying file modes.
b42074ab	63	.Sh BUGS
87150da0 DS	64	Since the text areas of sticky text executables are stashed in the swap area,
87150da0 DS	65	abuse of the feature can cause a system to run out of swap.
b42074ab	66	.Pp
87150da0	67	Neither
b42074ab	68	.Xr open 2
87150da0	69	nor
b42074ab	70	.Xr mkdir 2
87150da0	71	will create a file with the sticky bit set.
b42074ab CL	72	.Sh HISTORY
	73	A
	74	.Nm
	75	command appeared in Version 32V AT&T UNIX.