====== Ubuntu - Programs - Program can't find Shared Library at run-time ======

Error received when trying to run a program, such as **error while loading shared libraries**.

Symlinks on libraries work fine, as long as the final target they trace to exists and is accessible.

Possible solutions include:

  * Create a symlink to the library path.
  * Copy the library file to a directory listed in /etc/ld.so.conf.
  * Add the directory containing the library files to /etc/ld.so.conf.
  * Update the **LD_LIBRARY_PATH** environment variable.
  * Recompile program statically.

<WRAP info>
After any of the first 3, rerun **ldconfig** so the linker cache is updated.  You can then run **ldconfig -v** to verify it's resolvable.
</WRAP>

----

===== Create a symlink to the library path =====

Create a symlink to the library path in a directory listed in /etc/ld.so.conf (or /lib or /usr/lib).

Assuming that the library file is named libxyz.so and that /usr/local/lib is one of the directories listed in /etc/ld.so.conf.

Then

<code bash>
ln -s libxyz.so /usr/local/lib/libxyz.so
</code>


Then update the linker cache.

<code bash>
ldconfig
</code>

<WRAP info>
The runtime linker (usually /lib/ld.so or /lib/ld-linux.so with some version number in it) checks all of its configured directories for the library, and then links them in every time the program starts.
</WRAP>

Now run the program.

----

===== Copy the library file to a directory listed in /etc/ld.so.conf =====

Copy the library file to a directory listed in /etc/ld.so.conf (or /lib or /usr/lib) (defaults).

Assuming that the library file is named libxyz*

<code bash>
cat /etc/ld.so.conf
</code>

displays

<code>
include /etc/ld.so.conf.d/*.conf
</code>

<WRAP info>
Some Linux systems have the /etc/ld.so.conf file point directly to some directories, such as /usr/local/lib.  Ubuntu however references a seperate directory /etc/ld.so.conf.d where is reads in any *.conf file.  Simply create a new confile file with an extension ending in **.conf**.  Populate this file with the path that contains the library file.
</WRAP>

Then update the linker cache.

<code bash>
ldconfig
</code>

<WRAP info>
The runtime linker (usually /lib/ld.so or /lib/ld-linux.so with some version number in it) checks all of its configured directories for the library, and then links them in every time the program starts.
</WRAP>

Now run the program.

----

===== Add the directory containing libxyz* to /etc/ld.so.conf =====

Add the directory containing libxyz* to /etc/ld.so.conf.

<code bash>
vi /etc/ld.so.conf
</code>

and add this line

<file bash /etc/ld.so.conf>
/directory/where/libxyz* exists
</file>

Then update the linker cache.

<code bash>
ldconfig
</code>

<WRAP info>
The runtime linker (usually /lib/ld.so or /lib/ld-linux.so with some version number in it) checks all of its configured directories for the library, and then links them in every time the program starts.
</WRAP>

Now run the program.

----

===== Update your **LD_LIBRARY_PATH** environment variable =====

Add the directory containing the library files (or symbolic link) to your **LD_LIBRARY_PATH** environment variable.

<code bash>
set LD_LIBRARY_PATH=/directory/path/to/libxyz* 
</code>

Now run the program.

----

===== Recompile program statically =====

It will work, but don't bother.