102 lines
3.7 KiB
Groff
102 lines
3.7 KiB
Groff
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.\" Copyright (c) 1980, 1991 Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)sticky.8 6.4 (Berkeley) 3/16/91
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.\"
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.Dd March 16, 1991
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.Dt STICKY 8
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.Os BSD 4
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.Sh NAME
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.Nm sticky
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.Nd sticky text and append-only directories
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.Sh DESCRIPTION
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A special file mode, called the
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.Em sticky bit
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(mode S_ISVTX),
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is used to indicate special treatment
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for shareable executable files and directories.
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See
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.Xr chmod 2
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or
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the file
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.Pa /usr/include/sys/stat.h
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for an explanation of file modes.
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.Sh STICKY TEXT EXECUTABLE FILES
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An executable shareable file whose sticky bit is set
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will not be immediately discarded from swap space after execution.
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The kernel will hoard the text segment of the file for future
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reuse and avoid having to reload the program.
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Shareable text segments are normally placed
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in a least-frequently-used cache after use,
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and thus the `sticky bit' has little effect on commonly-used text images.
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.Pp
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Sharable executable files are created with the
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.Fl n
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and
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.Fl z
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options of
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the loader
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.Xr ld 1 .
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.Pp
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Only the super-user can set the sticky bit
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on a sharable executable file.
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.Sh STICKY DIRECTORIES
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A directory whose `sticky bit' is set
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becomes an append-only directory, or, more accurately,
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a directory in which the deletion of files is restricted.
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A file in a sticky directory may only be removed or renamed
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by a user if the user has write permission for the directory and
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the user is the owner of the file, the owner of the directory,
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or the super-user.
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This feature is usefully applied to directories such as
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.Pa /tmp
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which must be publicly writable but
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should deny users the license to arbitrarily
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delete or rename each others' files.
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.Pp
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Any user may create a sticky directory.
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See
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.Xr chmod 1
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for details about modifying file modes.
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.Sh BUGS
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Since the text areas of sticky text executables are stashed in the swap area,
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abuse of the feature can cause a system to run out of swap.
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.Pp
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Neither
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.Xr open 2
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nor
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.Xr mkdir 2
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will create a file with the sticky bit set.
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.Sh HISTORY
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A
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.Nm
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command appeared in Version 32V AT&T UNIX.
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