# Make a place for rxvt-unicode
mkdir rxvt-unicode
cd rxvt-unicode/
 
# Get the source
apt-get source rxvt-unicode
cd rxvt-unicode-8.4/
 
# Apply 256 color patch, it's included with the source
patch -p1 < doc/urxvt-8.2-256color.patch
 
# Make sure you have all depdencies to build it
sudo apt-get build-dep rxvt-unicode
 
# Build it
dpkg-buildpackage -us -uc -rfakeroot