ldconfig - configure dynamic linker run-time bindings
ldconfig creates, updates, and removes the necessary links and cache
(for use by the run-time linker, ld.so) to the most recent shared
libraries found in the directories specified on the command line, in
the file /etc/ld.so.conf, and in the trusted directories (/usr/lib and
/lib). ldconfig checks the header and file names of the libraries it
encounters when determining which versions should have their links
updated. ldconfig ignores symbolic links when scanning for libraries.
ldconfig will attempt to deduce the type of ELF libs (ie. libc 5.x or
libc 6.x (glibc)) based on what C libraries if any the library was
linked against, therefore when making dynamic libraries, it is wise to
explicitly link against libc (use -lc). ldconfig is capable of storing
multiple ABI types of libraries into a single cache on architectures
which allow native running of multiple ABIs, like ia32/ia64/x86_64 or
Some existing libs do not contain enough information to allow the
deduction of their type, therefore the /etc/ld.so.conf file format
allows the specification of an expected type. This is only used for
those ELF libs which we can not work out. The format is like this
"dirname=TYPE", where type can be libc4, libc5 or libc6. (This syntax
also works on the command line). Spaces are not allowed. Also see the
Directory names containing an = are no longer legal unless they also
have an expected type specifier.
ldconfig should normally be run by the super-user as it may require
write permission on some root owned directories and files. If you use
-r option to change the root directory, you dont have to be super-user
though as long as you have sufficient right to that directory tree.
Verbose mode. Print current version number, the name of each
directory as it is scanned and any links that are created.
-n Only process directories specified on the command line. Dont
process the trusted directories (/usr/lib and /lib) nor those
specified in /etc/ld.so.conf. Implies -N.
-N Dont rebuild the cache. Unless -X is also specified, links are
-X Dont update links. Unless -N is also specified, the cache is
Use conf instead of /etc/ld.so.conf.
Use cache instead of /etc/ld.so.cache.
Change to and use root as the root directory.
-l Library mode. Manually link individual libraries. Intended for
use by experts only.
Print the lists of directories and candidate libraries stored in
the current cache.
Use FORMAT for the cache file. Choices are old, new and compat
-? --help --usage
Print usage information.
Print version and exit.
# /sbin/ldconfig -v
will set up the correct links for the shared binaries and rebuild the
# /sbin/ldconfig -n /lib
as root after the installation of a new shared library will properly
update the shared library symbolic links in /lib.
/lib/ld-linux.so.* execution time linker/loader
/etc/ld.so.conf File containing a list of colon, space, tab, new
line, or comma separated directories in which to
search for libraries.
/etc/ld.so.cache File containing an ordered list of libraries found
in the directories specified in /etc/ld.so.conf.
This file is not in human readable format, and is
not intended to be edited.
lib*.so.version shared libraries
ldconfig, being a user process, must be run manually and has no means
of dynamically determining and relinking shared libraries for use by
ld.so when a new shared library is installed.
Andreas Jaeger. Manual page written by David Engel and Mitch DSouza.
27 August 2006 ldconfig(8)