You have installed some new libraries, but these are not available to programs and are not listed by ldconfig -p. What file should the path to the libraries be added to, before running ldconfig?

Answer: /etc/ld.so.conf

Explanation:
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 file names of the libraries it encounters when determining which versions should have their links updated.
Some files:
/lib/ld.so run-time linker/loader /etc/ld.so.conf File containing a list of colon, space, tab, newline, or comma spearated 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.