> Docker is useful if you have multiple applications with different versions of the same dependencies running on the same machine, as well as for deploying onto

> Docker is useful if you have multiple applications with different versions of the same dependencies running on the same machine, as well as for deploying onto any machine Different languages get a different amount of boost here. Ruby is an example which strongly benefits from docker deploys. You don't need to worry about what version of ruby (if any) will be installed on the host. And you don't need to worry about getting your gem dependencies installed on the host or figure out how to bundle them into your app code. I think older dot net apps required the runtime to be installed on the host. Docker would have helped then. The other big draw of docker is uniformity in deployment (the shipping container metaphor). Deploying code of any language and third party apps can be very similar. This is a powerful enough idea that giant abstractions like kubernetes have come to exist. This would be much more fiddly if each application needed to be special cased.