Deploying docker container as part of your continuous integration can cause your disk to fill up pretty quick. Docker does reuse the layers that did not change between deployments. But still, that last layer with you .war or .js bundle can take a few hundred megabytes. Taking into account, that you should be deploying a new version of every update of the master branch, this can take up a gigabyte every day. And you don’t really need all those old images and containers on your dev environment.