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diff --git a/docs/sources/faq.md b/docs/sources/faq.md index 667058c86f..b76a749fe1 100644 --- a/docs/sources/faq.md +++ b/docs/sources/faq.md @@ -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/dotcloud/docker) and |