Jupyter was deployed on one LXD container and Apache was deployed on another. At first Jupyter kept complaining “Connecting to kernel… Failed.”

Ubuntu: 16.04LTS

Apache: Server version: Apache/2.4.18 (Ubuntu)

Solution:

Add those two lines BEFORE “/” one:

ProxyPass /api/kernels/ ws://xxx.lxd:8888/api/kernels/
ProxyPassReverse /api/kernels/ http://xxx.lxd:8888/api/kernels/

AND: make sure proxy_wstunnel is enabled for Apache:

a2enmod proxy proxy_wstunnel