rxvt-unicode requires per-user configuration to work properly. A minimum
such configuration is provided by creating .Xresources, .Xdefaults and
.bashrc in the user's home directory, or adapting the existing files
there, in line with the examples in this directory. .bashrc at least is
almost certainly present, just add the line

export Term=xterm

Search the web for ideas for personalising and extending the
configuration. These configs are those used in the Salix Fluxbox
edition, which uses urxvt as its default terminal emulator.

Note that this version of .Xdefaults starts urxvt with tabbed:
SHIFT-arrow to switch tabs, SHIFT-down to create a new one -
alternatively, click on the top line with the mouse.