ldconfig - determine run-time link bindings
ldconfig creates 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. libc5 or
libc6/glibc) based on what C libs if any the library was linked
against, therefore when making dynamic libraries, it is wise to explicitly
link against libc (use -lc).
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. It is normally
run automatically at bootup, from /etc/rc, or manually whenever
new DLL's are installed.
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. Don't
process the trusted directories (/usr/lib and /lib) nor those
specified in /etc/ld.so.conf. Implies -N.
-N Don't rebuild the cache. Unless -X is also specified, links are
-X Don't 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.
In the bootup file /etc/rc having the line
will set up the correct links for the shared binaries and rebuild the
On the command line
# /sbin/ldconfig -n /lib
as root after the installation of a new DLL, will properly update the
shared library symbolic links in /lib.
execution time linker/loader
/etc/ld.so.conf File containing a list of colon, space, tab, newline,
or comma spearated 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's functionality, in conjunction with ld.so, is only available
for executables compiled using libc version 4.4.3 or greater.
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 DLL is installed.
David Engel and Mitch D'Souza.
30 September 2000 ldconfig(8)
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