apt-get install build-essential cmake libxerces-c2-dev omniorb libboost-all-dev doxygen
cd /usr/src
git clone git://gitorious.org/orocos-toolchain/rtt.git
export RTAI_ROOT_DIR=/usr/realtime
export RTAI_INCLUDE_DIR=$RTAI_ROOT_DIR/include
export RTAI_LIBRARY=$RTAI_ROOT_DIR/lib
you can also add this varible to ~/.bashrc (or ~/.zshrc)
cd /usr/src/rtt
mkdir build && cd build
cmake .. -DOROCOS_TARGET=lxrt
make
make install
enjoy it!