ldconfig(8): update manpage to reality
ELF ldconfig only maintains the search list, there is no hints Reviewed by: emaste Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D30272
This commit is contained in:
Konstantin Belousov
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c99d887ca8
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a19e14ca2d
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.\"
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.\" Copyright (c) 1993 Paul Kranenburg
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.\" All rights reserved.
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.\" Copyright (c) 2021 The FreeBSD Foundation, Inc.
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.\"
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.\" Portions of this documentation were written by
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.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
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.\" from the FreeBSD Foundation.
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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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@ -29,36 +34,40 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 31, 2020
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.Dd May 15, 2021
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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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.Nd configure the dynamic linker search path for shared libraries
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.Sh SYNOPSIS
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.Nm
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.Op Fl 32
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.Op 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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utility is used to configure the set of paths used by the dynamic linker
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.Xr ld-elf.so.1 1
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when searching for shared libraries.
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The dynamic linker looks for libraries in a set of built-in system directories
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and any directories specified in the hints file.
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This obviates the need for storing search paths within the executable,
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see the
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.Fl rpath
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option for the static linker
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.Xr ld 1 .
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.Pp
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Alternatively,
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The hints file is maintained by
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.Nm .
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The
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.Ar directories
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list to be stored in the hints file is supplied on the command line.
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.Pp
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Alternatively to the
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.Ar directories
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list on the command line,
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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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@ -67,9 +76,6 @@ 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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@ -77,16 +83,10 @@ 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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environment variable can be used to specify additional
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shared library search directories.
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.Ev LD_LIBRARY_PATH
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is a
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.Sq \&:
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@ -99,10 +99,6 @@ equivalent of the
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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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@ -112,12 +108,10 @@ on 64-bit systems that support running 32-bit binaries.
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.It Fl elf
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Ignored for backwards compatibility.
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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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Appends pathnames on the command line to the directory list from
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the hints file.
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.Pp
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This is the default action when no options 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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@ -125,19 +119,15 @@ This option is provided primarily for testing.
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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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Instead of replacing the list of the directories to search with the
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directories specified on the command line, merge existing list
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with the specified directories, and write the result to the hints file.
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.It Fl r
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List the current contents of the hints file
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List the current list of the directories from 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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.Pp
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Scan and print all libraries found on the directories list.
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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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@ -151,40 +141,31 @@ 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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the dynamic linker will only load shared libraries from paths found in
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the hints 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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Thus,
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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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serves to specify the trusted collection of directories from which
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shared objects can 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 ld-elf.so.1 ,
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.Xr link 5
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.Sh HISTORY
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A
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@ -192,8 +173,7 @@ A
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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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.Pp
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The name 'hints file' is historic from the times when the file also contained
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hints to the dynamic linker.
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This functionality is not provided for ELF.
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