Copyright (c) 1998 The NetBSD Foundation, Inc.
All rights reserved.
This code is derived from software contributed to The NetBSD Foundation
by Paul Kranenburg.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
.Dd October 8, 2000 .Dt LDCONFIG 8 .Os .Sh NAME .Nm ldconfig .Nd configure the a.out shared library cache .Sh SYNOPSIS .Nm ldconfig .Op Fl cmrsSv .Op Ar directory Ar ... .Sh DESCRIPTION .Nm is used to prepare a set of .Dq hints for use by the a.out run-time linker .Nm ld.so to facilitate quick lookup of shared libraries available in multiple directories. .Nm is only available on systems that use the .Dq a.out format for executables and libraries \(en on ELF systems, all the work is done by .Nm ld.elf_so .
p By default, it scans a set of built-in system directories, directories listed in
a /etc/ld.so.conf , and any .Ar directories specified on the command line (in the given order) looking for shared libraries and stores the results in the file
a /var/run/ld.so.hints to forestall the overhead that would otherwise result from the directory search operations .Nm ld.so would have to perform to load required shared libraries.
p The shared libraries so found will be automatically available for loading if needed by the program being prepared for execution. This obviates the need for storing search paths within the executable.
p The .Ev LD_LIBRARY_PATH environment variable can be used to override the use of directories (or the order thereof) from the cache or to specify additional directories where shared libraries might be found. .Ev LD_LIBRARY_PATH is a .Sq : separated list of directory paths that are searched by .Nm ld.so when it needs to load a shared library. It can be viewed as the run-time equivalent of the .Fl L switch of .Nm ld .
p .Nm is typically run as part of the boot sequence.
p The following options are recognized by .Nm ldconfig : l -tag -width indent t Fl c Do not scan directories listed in
a /etc/ld.so.conf for shared libraries. t Fl m Merge the result of the scan of the directories given as arguments into the existing hints file. The default action is to build the hints file afresh. t Fl r Lists the current contents of
a ld.so.hints on the standard output. The hints file will not be modified. t Fl s Do not scan the built-in system directory
q Pa /usr/lib , nor any directories listed in
a /etc/ld.so.conf for shared libraries. t Fl S Do not scan the built-in system directory
q Pa /usr/lib , for shared libraries. (Directories listed in
a /etc/ld.so.conf are still scanned.) t Fl v Switch on verbose mode. .El .Sh FILES
a /var/run/ld.so.hints ,
a /etc/ld.so.conf .Sh SEE ALSO .Xr ld 1 , .Xr ld.so 1 , .Xr ld.so.conf 5 , .Xr link 5 .Sh HISTORY A .Nm utility first appeared in SunOS 4.0, it appeared in its current form in .Nx 0.9a . .Sh SECURITY CONSIDERATIONS Special care must be taken when loading shared libraries into the address space of .Em set-user-ID programs. Whenever such a program is run, .Nm ld.so will only load shared libraries from the
a ld.so.hints file. In particular, the .Ev LD_LIBRARY_PATH and .Ev LD_PRELOAD is not used to search for libraries. Thus, the role of ldconfig is dual. In addition to building a set of hints for quick lookup, it also serves to specify the trusted collection of directories from which shared objects can be safely loaded. It is presumed that the set of directories specified to .Nm is under control of the system's administrator. .Nm ld.so further assists set-user-ID programs by erasing the .Ev LD_LIBRARY_PATH and .Ev LD_PRELOAD from the environment.
Indexes created Fri Sep 26 08:10:20 GMT 2025