These instructions have been tested on a fresh digital ocean instance:
Specs: Standard / 1 GB / 1 vCPU / 1 GB Memory / 25 GB Disk / SGP1 - Ubuntu 18.04.3 (LTS) x64
$ uname -a
Linux test-watcher-ubuntu-s-1vcpu-1gb-sgp1-01 4.15.0-66-generic #75-Ubuntu SMP Tue Oct 1 05:24:09 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux