We encountered this error recently when upgrading our ClamAV to 0.95 and ran into a problem where we got the error :

LibClamAV Warning: Cannot dlopen: file not found – unrar support unavailable

The solution to this is quite simple:

Create a symlink like so:

ln /usr/lib/libclamunrar_iface.so.6 /usr/lib/libclamunrar_iface.so

If you installed the x86_64 version, you need to run the following command:

ln /usr/lib64/libclamunrar_iface.so.6 /usr/lib64/libclamunrar_iface.so

Then restart clamav by running:

service clamd restart

If you encounter the same error, run ldconfig.