Except discourse/INSTALL-cloud.md at master · discourse/discourse · GitHub says to
wget -qO- https://get.docker.com/ | sh
Which the “official docs” say "Using these scripts is not recommended for production environments, " I think that they issue that warning mostly because blindly trusting someone else’s script with root access to your system is foolhardy from a security standpoint.
If find Docker’s official docs to be surprisingly difficult to make sense of. And why don’t they include docker-compose in the Linux binaries, when they do for Mac and Windows?
Well, if you installed it using the get.docker.com approach, it’s just as safe to use it to upgrade. You get a warning and have to wait 20 seconds, but it generally works.