When you modify /etc/ld.so.conf, it won't have any effect until you regenerate /etc/ld.so.cache with ldconfig! Manpage for ld.so misleadingly mentions ld.so.conf while it doesn't affect dynamic loader's behaviour in any way.

In practice this is important when you create a chroot environment. Copying host's ld.so.cache into chroot would be wrong ( Read more... )