ldconfig

Examples (TL;DR)

• Update symlinks and rebuild the cache (usually run when a new library is installed): sudo ldconfig
• Update the symlinks for a given directory: sudo ldconfig -n path/to/directory
• Print the libraries in the cache and check whether a given library is present: ldconfig -p | grep library_name

tldr.sh

Synopsis

/sbin/ldconfig [-nNvXV] [-f conf] [-C cache] [-r root] directory...

/sbin/ldconfig -l [-v] library...

/sbin/ldconfig -p

Description

ldconfig creates the necessary links and cache 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, /lib and /usr/lib (on some 64-bit architectures such as x86-64, /lib and /usr/lib are the trusted directories for 32-bit libraries, while /lib64 and /usr/lib64 are used for 64-bit libraries).

The cache is used by the run-time linker, ld.so or ld-linux.so. ldconfig checks the header and filenames of the libraries it encounters when determining which versions should have their links updated.

ldconfig will attempt to deduce the type of ELF libraries (i.e., libc5 or libc6/glibc) based on what C libraries, if any, the library was linked against.

Some existing libraries 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 used only for those ELF libraries which we can not work out. The format is "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. ldconfig should normally be run by the superuser as it may require write permission on some root owned directories and files.

Options

-c fmt, --format=fmt

(Since glibc 2.2) Cache format to use: old, new, or compat (default).

-C cache

Use cache instead of /etc/ld.so.cache.

-f conf

Use conf instead of /etc/ld.so.conf.

-i, --ignore-aux-cache

(Since glibc 2.7) Ignore auxiliary cache file.

-l

(Since glibc 2.2) Library mode. Manually link individual libraries. Intended for use by experts only.

-n

Process only the directories specified on the command line. Don't process the trusted directories, nor those specified in /etc/ld.so.conf. Implies -N.

-N

Don't rebuild the cache. Unless -X is also specified, links are still updated.

-p, --print-cache

Print the lists of directories and candidate libraries stored in the current cache.

-r root

Change to and use root as the root directory.

-v, --verbose

Verbose mode. Print current version number, the name of each directory as it is scanned, and any links that are created. Overrides quiet mode.

-V, --version

Print program version.

-X

Don't update links. Unless -N is also specified, the cache is still rebuilt.

Files

/lib/ld.so

Run-time linker/loader.

/etc/ld.so.conf

File containing a list of directories, one per line, 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, as well as those found in the trusted directories.

See Also

ldd(1), ld.so(8)

Colophon

This page is part of release 5.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Referenced By

dlopen(3), dpkg-divert(1), env-update(1), fakechroot(1), hamlib-primer(7), ldconfig_selinux(8), ldd(1), ld.so(8), rtld-audit(7), sln(8).