How to install additional kernel to ipython / jupyter?

Assuming you already have python 3 and ipython installed with anaconda,

Create python 2.7 env
$ conda create -n py27 python=2.7

Activate the env
$ source activate py27

Install ipykernel
$ conda install notebook ipykernel

Write kernel spec
$ ipython kernelspec install-self --user
which should write to ~/.local/share/jupyter/kernels/python2

Deactivate 2.7 env
$ source deactivate

link the kernel spec to the location where ipython will read
$ cd ~/.ipython/
$ ln -s ~/.local/share/jupyter/kernels/

Confirm now that we have additional kernel
$ ipython kernelspec list

Start ipython notebook and you should now have both kernels
$ ipython notebook --no-browser