ldconfig(8) - NetBSD Manual Pages

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


NAME

     ldconfig -- configure the a.out shared library cache


SYNOPSIS

     ldconfig [-cmrsSv] [directory ...]


DESCRIPTION

     ldconfig is used to prepare a set of ``hints'' for use by the a.out run-
     time linker ld.so to facilitate quick lookup of shared libraries avail-
     able in multiple directories.  ldconfig is only available on systems that
     use the ``a.out'' format for executables and libraries - on ELF systems,
     all the work is done by ld.elf_so.

     By default, it scans a set of built-in system directories, directories
     listed in /etc/ld.so.conf, 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 result from the directory search operations ld.so would
     have to perform to load 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 that are
     searched by ld.so when it needs to load a shared library.  It can be
     viewed as the run-time equivalent of the -L switch of ld.

     ldconfig is typically run as part of the boot sequence.

     The following options are recognized by ldconfig:

     -c      Do not scan directories listed in /etc/ld.so.conf for shared
             libraries.

     -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.

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

     -s      Do not scan the built-in system directory (/usr/lib), nor any
             directories listed in /etc/ld.so.conf for shared libraries.

     -S      Do not scan the built-in system directory (/usr/lib), for shared
             libraries.  (Directories listed in /etc/ld.so.conf are still
             scanned.)

     -v      Switch on verbose mode.


FILES

     /var/run/ld.so.hints, /etc/ld.so.conf


SEE ALSO

     ld(1), ld.so(1), ld.so.conf(5), link(5)


HISTORY

     A ldconfig utility first appeared in SunOS 4.0, it appeared in its cur-
     rent form in NetBSD 0.9A.


SECURITY CONSIDERATIONS

     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
     will only load shared libraries from the ld.so.hints file.  In particu-
     lar, the LD_LIBRARY_PATH and 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 ldconfig is under
     control of the system's administrator.  ld.so further assists set-user-ID
     programs by erasing the LD_LIBRARY_PATH and LD_PRELOAD from the environ-
     ment.

NetBSD 3.0                      October 8, 2000                     NetBSD 3.0