# apt-file search libXrender.so.1
libxrender1: /usr/lib/i386-linux-gnu/libXrender.so.1
libxrender1: /usr/lib/i386-linux-gnu/libXrender.so.1.3.0
libxrender1-dbg: /usr/lib/debug/usr/lib/i386-linux-gnu/libXrender.so.1.3.0
If you need to install apt-file:
# apt-get install apt-file
# apt-file update
