# Usage

This directory contains a skylark rule to generate the toolchain configs. See README.md under
the root directory for the definition of toolchain configs.

For a given version of Bazel, the `docker_toolchain_autoconfig` rule will:
* build the execution container image,
* install Bazel,
* build the container, and
* extract the toolchain config.

Refer to the documentation in docker_config.bzl for more details of how to execute this rule
and how to extract the toolchain configs.

The BUILD file in this directory contains 3 sample `docker_toolchain_autoconfig` targets which
use Bazel 0.7.0 to generate toolchain configs for:
* Debian8 Clang environment,
* Ubuntu Trusty GCC environment, and
* Ubuntu Xenial GCC environment.

# Authentication

If you are generating toolchain configs for the first time, you will probably encounter permission
issues. You can use [`docker-credential-gcr`](https://github.com/bazelbuild/rules_docker#authorization)
to enable `docker` to talk to `gcr.io` directly by executing the following commands:

```shell
gcloud components install docker-credential-gcr
docker-credential-gcr configure-docker
```