configure the shared library
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 result from the directory search operations
ld.so(1) would have to perform to load the required shared
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.
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
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
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
rc.conf(8) for further information.
The following options are recognized by
- 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. This option cannot be used with
- 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.
- List the current contents of ld.so.hints on the standard output. The hints file will not be modified.
- Do not scan the built-in system directory (“/usr/lib”) for shared libraries.
- Unconfigure directories specified on the command line or remove
inaccessible directories from search path if no directories specified.
This option cannot be used with
- Switch on verbose mode.
Special care must be taken when loading shared libraries into the
address space of set-user-ID and set-group-ID programs. Whenever such a
program is run, ld.so(1) will only load shared libraries from the
ld.so.hints file. In particular, 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 directories 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 and set-group-ID
programs by erasing the
LD_LIBRARY_PATH from the
- Additional directories containing shared libraries, settable in the user's environment.
- Additional directories containing shared libraries, settable in /etc/rc.conf.local.
ld(1), elf(5), rc.conf(8)
ldconfig utility first appeared in
SunOS 4.0. It appeared in its current form in NetBSD