Antes de ejecutar Firefox hay que instalar los siguientes paquetes:

dpkg –add-architecture i386

aptitude install libc6:i386 gcc-4.8-base:i386 libc6-i686:i386 libgcc1:i386 libfontconfig1:i386 libxrender1:i386 libfreetype6:i386 libx11-6:i386 lib32stdc++6 libxext6:i386 libxdamage1:i386 libxcomposite1:i386 libasound2:i386 libdbus-glib-1-2:i386 libgtk2.0-0:i386 libxt6:i386