202 lines
6.3 KiB
Groff
202 lines
6.3 KiB
Groff
.\"
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.\" Copyright (c) 1993 Paul Kranenburg
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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 Paul Kranenburg.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 6, 2018
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.Dt LDCONFIG 8
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.Os
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.Sh NAME
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.Nm ldconfig
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.Nd configure the shared library cache
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.Sh SYNOPSIS
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.Nm
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.Op Fl 32
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.Op Fl aout | Fl elf
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.Op Fl Rimrsv
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.Op Fl f Ar hints_file
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.Op Ar directory | Ar
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.Sh DESCRIPTION
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The
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.Nm
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utility is used to prepare a set of
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.Dq hints
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for use by the dynamic linker
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to facilitate quick lookup of shared libraries available in multiple
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directories.
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It scans a set of built-in system directories and any
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.Ar directories
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specified on the command line (in the given order) looking for
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shared libraries and stores the results in a system file to forestall
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the overhead that would otherwise result from the directory search
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operations the dynamic linker would have to perform to load the
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required shared libraries.
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.Pp
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Alternatively,
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.Ar files
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may be specified; these are expected to contain directories
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to scan for shared libraries.
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Each directory's pathname must start on a new
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line.
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Blank lines and lines starting with the comment character
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.Ql \&#
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are ignored.
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Filenames must conform to the
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.Pa lib*.so.[0-9]
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pattern in order to be added to the hints file.
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.Pp
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For security reasons, directories which are world or group-writable or which
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are not owned by root produce warning messages and are skipped, unless
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the
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.Fl i
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option is present.
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.Pp
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The shared libraries which are found will be automatically available for loading
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if needed by the program being prepared for execution.
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This obviates the need
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for storing search paths within the executable.
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.Pp
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The
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.Ev LD_LIBRARY_PATH
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environment variable can be used to override the use of
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directories (or the order thereof) from the cache or to specify additional
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directories where shared libraries might be found.
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.Ev LD_LIBRARY_PATH
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is a
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.Sq \&:
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separated list of directory paths which are searched by
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the dynamic linker
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when it needs to load a shared library.
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It can be viewed as the run-time
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equivalent of the
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.Fl L
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switch of
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.Xr ld 1 .
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.Pp
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The
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.Nm
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utility is typically run as part of the boot sequence.
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.Pp
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The following options are recognized by
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.Nm :
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.Bl -tag -width indent
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.It Fl 32
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Generate the hints for 32-bit ABI shared libraries
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on 64-bit systems that support running 32-bit binaries.
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.It Fl aout
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Generate the hints for a.out format shared libraries.
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.It Fl elf
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Generate the hints for ELF format shared libraries.
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.It Fl R
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Rescan the previously configured directories.
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This opens the previous hints
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file and fetches the directory list from the header.
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Any additional pathnames
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on the command line are also processed.
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This is the default action when no parameters are given.
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.It Fl f Ar hints_file
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Read and/or update the specified hints file, instead of the standard file.
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This option is provided primarily for testing.
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.It Fl i
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Run in insecure mode.
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The security checks will not be performed.
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.It Fl m
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Instead of replacing the contents of the hints file
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with those found in the directories specified,
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.Dq merge
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in new entries.
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Directories recorded in the hints file by previous runs of
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.Nm
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are also rescanned for new shared libraries.
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.It Fl r
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List the current contents of the hints file
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on the standard output.
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The hints file is not modified.
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The list of
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directories stored in the hints file is included.
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.It Fl s
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Do not scan the built-in system directory
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.Pq Dq /usr/lib
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for shared libraries.
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.It Fl v
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Switch on verbose mode.
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.El
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.Sh SECURITY
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Special care must be taken when loading shared libraries into the address
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space of
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.Ev set-user-Id
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programs.
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Whenever such a program is run by any user except the owner of the program,
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the dynamic linker
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will only load shared libraries from the hints
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file.
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In particular, the
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.Ev LD_LIBRARY_PATH
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is not used to search for libraries.
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Thus, the role of
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.Nm
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is dual.
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In addition to building a set of hints for quick lookup, it also serves to
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specify the trusted collection of directories from which shared objects can
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be safely loaded.
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.Sh FILES
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.Bl -tag -width /var/run/ld-elf.so.hintsxxx -compact
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.It Pa /var/run/ld.so.hints
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Standard hints file for the a.out dynamic linker.
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.It Pa /var/run/ld-elf.so.hints
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Standard hints file for the ELF dynamic linker.
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.It Pa /etc/ld.so.conf
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Conventional configuration file containing directory names for
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invocations with
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.Fl aout .
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.It Pa /etc/ld-elf.so.conf
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Conventional configuration file containing directory names for
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invocations with
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.Fl elf .
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.It Pa /var/run/ld-elf32.so.hints
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.It Pa /var/run/ld32.so.hints
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Conventional configuration files containing directory names for
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invocations with
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.Fl 32 .
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.El
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.Sh SEE ALSO
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.Xr ld 1 ,
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.Xr link 5
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.Sh HISTORY
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A
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.Nm
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utility first appeared in SunOS 4.0, it appeared in its current form
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in
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.Fx 1.1 .
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.Sh BUGS
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Some security checks (for example, verifying root ownership of
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added directories) are not performed when
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.Fl aout
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is specified.
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