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# ldconfig - Unix, Linux Command

# NAME

/sbin/ldconfig - configure dynamic linker run time bindings

# 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). 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 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 "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

Tag | Description
--- | ---
-v | Verbose mode. Print current version number, the name of each directory as it is scanned, and any links that are created. Overrides quiet mode.
-n | Only process directories specified on the command line. Don’t process the trusted directories (/lib and /usr/lib) 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.
-X | Don’t update links. Unless -N is also specified, the cache is still rebuilt.
-f conf | Use conf instead of /etc/ld.so.conf.
-C cache | Use cache instead of /etc/ld.so.cache.
-r root | Change to and use root as the root directory.
-l | Library mode. Manually link individual libraries. Intended for use by experts only.
-p | Print the lists of directories and candidate libraries stored in the current cache.

# FILES

Tag | Description
--- | ---
/lib/ld.so | run-time linker/loader
/etc/ld.so.conf | File containing a list of colon, space, tab, newline, 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.

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