1.\" $OpenBSD: sticky.8,v 1.10 2014/02/14 17:27:58 schwarze Exp $ 2.\" $NetBSD: sticky.8,v 1.3 1994/11/30 19:36:27 jtc Exp $ 3.\" 4.\" Copyright (c) 1980, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)sticky.8 8.1 (Berkeley) 6/5/93 32.\" 33.Dd $Mdocdate: February 14 2014 $ 34.Dt STICKY 8 35.Os 36.Sh NAME 37.Nm sticky 38.Nd sticky text and append-only directories 39.Sh DESCRIPTION 40A special file mode, called the 41.Em sticky bit 42(mode S_ISVTX), 43is used to indicate special treatment for files and directories. 44See 45.Xr chmod 2 46or 47the file 48.Pa /usr/include/sys/stat.h 49for an explanation of file modes. 50.Sh STICKY FILES 51Historically, an executable shareable file which had the sticky bit set 52was not immediately discarded from swap space after execution. 53The kernel hoarded the text segment of the file for future reuse, 54thus avoiding having to reload the program. 55This is no longer true on modern systems; 56the current virtual memory system keeps track of recently used executables, 57making the sticky bit for files redundant. 58The sticky bit can still be set on files, but without any effect. 59.Pp 60Only the superuser can set the sticky bit on a file, 61though the owner of the file may clear the sticky bit. 62.Sh STICKY DIRECTORIES 63A directory with the 64.Sq sticky bit 65set places restrictions on file deletion: 66a file in a sticky directory may only be removed or renamed 67by a user if the user has write permission for the directory and 68the user is the owner of the file, the owner of the directory, 69or the superuser. 70This feature is usefully applied to directories such as 71.Pa /tmp 72which must be publicly writable but 73should deny users the license to arbitrarily 74delete or rename each others' files. 75.Pp 76Any user may create a sticky directory. 77See 78.Xr chmod 1 79for details about modifying file modes. 80.Sh HISTORY 81A 82.Nm 83command appeared in 84.At 32v . 85.Sh BUGS 86Neither 87.Xr open 2 88nor 89.Xr mkdir 2 90will create a file with the sticky bit set. 91