LDCONFIG(8)             OpenBSD System Manager's Manual            LDCONFIG(8)

NAME
     ldconfig - configure the shared library cache

SYNOPSIS
     ldconfig [-DmPRrSsUv] [path ...]

DESCRIPTION
     ldconfig is used to prepare a set of ``hints'' for use by the run-time
     linker ld.so(1) to facilitate quick lookup of shared libraries available
     in multiple directories.  It scans a set of built-in system directories
     and any directories specified on the command line (in the given order)
     looking for shared libraries and stores the results in the file
     /var/run/ld.so.hints to forestall the overhead that would otherwise re-
     sult from the directory search operations ld.so(1) would have to perform
     to load the required shared libraries.

     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.

     The LD_LIBRARY_PATH environment variable can be used to override the use
     of directories (or the order thereof) from the cache or to specify addi-
     tional directories where shared libraries might be found.
     LD_LIBRARY_PATH is a `:' separated list of directory paths which are
     searched by ld.so(1) when it needs to load a shared library.  It can be
     viewed as the run-time equivalent of the -L switch of ld(1).

     ldconfig is typically run as part of the boot sequence.  In addition to
     the built-in system directories, directories containing shared libraries
     may be specified via the shlib_dirs variable in /etc/rc.conf.local.  See
     rc.conf(8) for further information.

     The following options are recognized by ldconfig:

     -D      Remove any prebind information in the specified binary or shared
             library.

     -m      Merge the result of the scan of the directories given as argu-
             ments into the existing hints file.  The default action is to
             build the hints file afresh.  This option cannot be used with -U.

     -P      Create and append prebind information to all executables found in
             the specified directories, and also all shared libraries which
             are required by those executables.

     -R      Rescan the previously configured directories.  This opens the
             hints file and fetches the directory list from the header.  Any
             additional pathnames on the command line are also processed.

     -r      List the current contents of ld.so.hints on the standard output.
             The hints file will not be modified.

     -S      Perform prelinking operations in a safe mode; always copies the
             binaries when prelinking data is added to a file.  Use this to
             eliminate the possibility that ETXTBUSY will occur when attempt-
             ing to run a binary while prelinking is running.

     -s      Do not scan the built-in system directory (``/usr/lib'') for
             shared libraries.

     -U      Unconfigure directories specified on the command line or remove
             inaccessible directories from search path if no directories spec-
             ified.  This option cannot be used with -m.

     -v      Switch on verbose mode.

PREBINDING
     Prebinding is loosely based on an earlier concept called Prelinking,
     which also accelerated ld.so(1) performance but simultaneously impaired
     address space randomization.  When prebinding information is added to li-
     braries and programs using -P, program startup can be significantly im-
     proved because ld.so(1) can initialize the shared library environment
     much faster.  Prebinding information adds a small amount of data to the
     end of each specified program and associated shared libraries.

SECURITY
     Special care must be taken when loading shared libraries into the address
     space of set-user-Id programs.  Whenever such a program is run, ld.so(1)
     will only load shared libraries from the ld.so.hints file.  In particu-
     lar, the LD_LIBRARY_PATH 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 direc-
     tories from which shared objects can be safely loaded.  It is presumed
     that the set of directories specified to ldconfig are under control of
     the system's administrator.  ld.so(1) further assists set-user-Id pro-
     grams by erasing the LD_LIBRARY_PATH from the environment.

ENVIRONMENT
     LD_LIBRARY_PATH
             Additional directories containing shared libraries, settable in
             the user's environment.

     shlib_dirs
             Additional directories containing shared libraries, settable in
             /etc/rc.conf.local.

FILES
     /etc/rc.conf
     /etc/rc.conf.local
     /var/run/ld.so.hints

SEE ALSO
     ld(1), link(5), rc.conf(8)

HISTORY
     An ldconfig utility first appeared in SunOS 4.0.  It appeared in its cur-
     rent form in NetBSD 0.9A.

OpenBSD 4.7                      May 31, 2007                                2
