Manpage of ldconfig


Section: Maintenance Commands (8)
Updated: 30 September 2000
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ldconfig - determine run-time link bindings  


ldconfig [OPTION...]  


ldconfig creates the necessary links and cache (for use by the run-time linker, to the most recent shared libraries found in the directories specified on the command line, in the file /etc/, 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/ 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 -p option.

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.  


-v --verbose
Verbose mode. Print current version number, the name of each directory as it is scanned and any links that are created.
Only process directories specified on the command line. Don't process the trusted directories (/usr/lib and /lib) nor those specified in /etc/ Implies -N.
Don't rebuild the cache. Unless -X is also specified, links are still updated.
Don't update links. Unless -N is also specified, the cache is still rebuilt.
-f conf
Use conf instead of /etc/
-C cache
Use cache instead of /etc/
-r root
Change to and use root as the root directory.
Library mode. Manually link individual libraries. Intended for use by experts only.
-p --print-cache
Print the lists of directories and candidate libraries stored in the current cache.
-c --format=FORMAT
Use FORMAT for the cache file. Choices are old, new and compat (the default).
-? --help --usage
Print usage information.
-V --version
Print version and exit.


In the bootup file /etc/rc having the line

/sbin/ldconfig -v

will set up the correct links for the shared binaries and rebuild the cache.
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.



/lib/, /lib/*
execution time linker/loader
File containing a list of colon, space, tab, newline, or comma spearated directories in which to search for libraries.
File containing an ordered list of libraries found in the directories specified in /etc/ This file is not in human readable format, and is not intended to be edited.
shared libraries




ldconfig's functionality, in conjunction with, 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 when a new DLL is installed.  


David Engel and Mitch D'Souza.




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Time: 23:31:01 GMT, March 03, 2024