Is /Usr/Local/Lib Searched for Shared Libraries

Is /usr/local/lib searched for shared libraries?

Make sure your LD_LIBRARY_PATH is set up to include all directories you want to search and then test it again.

You can test this quickly with:

LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib ffmpeg

which will set it only for that invocation.

Alternatively, you can edit /etc/ld.so.conf which contains the default directories searched. Some Linux distributions may not include /usr/local/lib in that file.

Note that you may also need to update the cache /etc/ld.so.cache by running ldconfig (as root, or with sudo).

Shared library not found in /usr/local/lib

Figured it out. While library names have to be prefixed with "lib", that prefix must not be specified when linking. That is, gcc -o prog main.c -llibt is wrong while gcc -o prog main.c -lt works as expected.

How does processes find shared libraries in folders under /usr/lib

Individual programs can control where they search for their libraries.

Also the search path can be controlled using the LD_LIBRARY_PATH env var:
http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html

Try appending /usr/lib/foo to your LD_LIBRARY_PATH env var.

Linux : error loading libraries from /usr/local/lib

Can anyone suggest what could be wrong?

If setting LD_LIBRARY_PATH solves the problem, it's almost certain that you didn't add /usr/local/lib to /etc/ld.so.conf.d/ correctly.

Which file in /etc/ld.so.conf.d/ did you add to?

Maybe you have a typo, or a trailing space, or something.

Shared library in /usr/local/lib not found

gcc -print-search-dirs will tell you what path the compiler checks. /usr/local/lib is simply not among them, so your compile time linker (in this case the new gold ld from binutils) doesn't find the library while the dynamic one (ld-linux.so which reads the cache written by ldconfig) does. Presumably the builds you've done previously added -L/usr/local/lib as necessary in their makefiles (usually done by a ./configure script), or you installed binaries.

Why linux doesn't search for shared libraries in the same folder

Adding . to LD_LIBRARY_PATH is generally not recommended as it introduces security risk and also makes program behavior less predictable for the end user. If you absolutely want to go down this path and want to avoid explicit setting of LD_LIBRARY_PATH, you can

• link with -Wl,-rpath -Wl,'$ORIGIN'
• not call your app directly but rather through a wrapper shell script which would set proper LD_LIBRARY_PATH and then run the app

Cannot access local shared library from /usr/local/lib

Did you modify by yourself /etc/ld.so.conf.d/libc.conf ?

If yes, then run (as root) ldconfig to re-read the config.

gcc: linked libraries in /usr/local/lib are not found, but /etc/ld/so.conf.d/libc.conf lists it?

You should run ldconfig (as root) after every change of the directories configured via /etc/ld.so.conf or under /etc/ld.so.conf.d/, in particular in your case after every update inside /usr/local/lib (e.g. after every addition or update of some shared libraries there).

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