Run update.sh

django/README.md

@@ -62,6 +62,22 @@ $ docker run -it --rm --user "$(id -u):$(id -g)" -v "$PWD":/usr/src/app -w /usr/
 
 This will create a sub-directory named `mysite` inside your current directory.
 
+# Image Variants
+
+The `django` images come in many flavors, each designed for a specific use case.
+
+## `django:<version>`
+
+This is the defacto image. If you are unsure about what your needs are, you probably want to use this one. It is designed to be used both as a throw away container (mount your source code and start the container to start your app), as well as the base to build other images off of.
+
+## `django:onbuild`
+
+This image makes building derivative images easier. For most use cases, creating a `Dockerfile` in the base of your project directory with the line `FROM django:onbuild` will be enough to create a stand-alone image for your project.
+
+While the `onbuild` variant is really useful for "getting off the ground running" (zero to Dockerized in a short period of time), it's not recommended for long-term usage within a project due to the lack of control over *when* the `ONBUILD` triggers fire (see also [`docker/docker#5714`](https://github.com/docker/docker/issues/5714), [`docker/docker#8240`](https://github.com/docker/docker/issues/8240), [`docker/docker#11917`](https://github.com/docker/docker/issues/11917)).
+
+Once you've got a handle on how your project functions within Docker, you'll probably want to adjust your `Dockerfile` to inherit from a non-`onbuild` variant and copy the commands from the `onbuild` variant `Dockerfile` (moving the `ONBUILD` lines to the end and removing the `ONBUILD` keywords) into your own file so that you have tighter control over them and more transparency for yourself and others looking at your `Dockerfile` as to what it does. This also makes it easier to add additional requirements as time goes on (such as installing more packages before performing the previously-`ONBUILD` steps).
+
 # License
 
 View [license information](https://github.com/django/django/blob/master/LICENSE) for the software contained in this image.