@@ -225,6 +225,38 @@ Downloading and installing an "all-in-one" .deb or .rpm sounds great at first,

 except if you have no way to figure out that it contains a copy of the

 OpenSSL library vulnerable to the [Heartbleed](http://heartbleed.com/) bug.

+### Why is `DEBIAN_FRONTEND=noninteractive` discouraged in Dockerfiles?

+

+When building Docker images on Debian and Ubuntu you may have seen errors like:

+

+    unable to initialize frontend: Dialog

+

+These errors don't stop the image from being built but inform you that the

+installation process tried to open a dialog box, but was unable to. 

+Generally, these errors are safe to ignore.

+

+Some people circumvent these errors by changing the `DEBIAN_FRONTEND` 

+environment variable inside the Dockerfile using:

+

+    ENV DEBIAN_FRONTEND=noninteractive

+

+This prevents the installer from opening dialog boxes during installation 

+which stops the errors.

+

+While this may sound like a good idea, it *may* have side effects. 

+The `DEBIAN_FRONTEND` environment variable will be inherited by all 

+images and containers built from your image, effectively changing

+their behavior. People using those images will run into problems when

+installing software interactively, because installers will not show

+any dialog boxes.

+

+Because of this, and because setting `DEBIAN_FRONTEND` to `noninteractive` is

+mainly a 'cosmetic' change, we *discourage* changing it.

+

+If you *really* need to change its setting, make sure to change it

+back to its [default value](https://www.debian.org/releases/stable/i386/ch05s03.html.en) 

+afterwards.

+

 ### Can I help by adding some questions and answers?

 Definitely! You can fork [the repo](https://github.com/docker/docker) and