Caches and offline mode

Since retrieving and transforming operating system image files, git repositories, Python or Ruby packages, and so on can be a significant overhead, we cache many of the inputs to the build process.

The cache location is read from DIB_IMAGE_CACHE. Developing Elements describes the interface within disk-image-builder for caching.

When invoking disk-image-builder, the --offline option will instruct disk-image-builder to not refresh cached resources. Alternatively you can set DIB_OFFLINE=1.

Note that we don’t maintain operating system package caches, instead depending on your local infrastructure (e.g. Squid cache, or an APT or Yum proxy) to facilitate caching of that layer, so you need to arrange independently for offline mode. For more information about setting up a squid proxy, consult the TripleO documentation.

Base images

These are cached by the standard elements - fedora, redhat-common, ubuntu, debian and opensuse.


Git repositories and tarballs obtained via the source-repositories element will be cached.


The pypi element will bind mount a PyPI mirror from the cache dir and configure pip and easy-install to use it.