# 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 - ../elements/fedora/README, ../elements/redhat-common/README, ../elements/ubuntu/README, ../elements/debian/README and ../elements/opensuse/README.

## source-repositories

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

## PyPI

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

this page last updated: 2023-06-08 20:53:31

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