Use CERN CentOS7 + CMSSW docker images from here: https://hub.docker.com/r/clelange/cc7-cmssw-cvmfs (required packages downloaded on-the-fly from CERN's SW repository cvmfs)
Majorly, these three stated below are to be done to complete the setup:
- Install docker on the local machine
- Pull and run CMSSW docker image
- Test externals via docker