Proxy Arguments and Build Tool Configuration Variables

4th chunk of `content/manuals/build/building/variables.md`

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Proxy arguments are automatically excluded from the build cache
and the output of `docker history` by default.
If you do reference the arguments in your Dockerfile,
the proxy configuration ends up in the build cache.

The builder respects the following proxy build arguments.
The variables are case insensitive.

- `HTTP_PROXY`
- `HTTPS_PROXY`
- `FTP_PROXY`
- `NO_PROXY`
- `ALL_PROXY`

To configure a proxy for your build:

```console
$ docker build --build-arg HTTP_PROXY=https://my-proxy.example.com .
```

For more information about proxy build arguments, refer to
[Proxy arguments](/reference/dockerfile.md#predefined-args).

## Build tool configuration variables

The following environment variables enable, disable, or change the behavior of Buildx and BuildKit.
Note that these variables aren't used to configure the build container;
they aren't available inside the build and they have no relation to the `ENV` instruction.
They're used to configure the Buildx client, or the BuildKit daemon.

| Variable                                                                    | Type              | Description                                                      |
|-----------------------------------------------------------------------------|-------------------|------------------------------------------------------------------|
| [BUILDKIT_COLORS](#buildkit_colors)                                         | String            | Configure text color for the terminal output.                    |
| [BUILDKIT_HOST](#buildkit_host)                                             | String            | Specify host to use for remote builders.                         |
| [BUILDKIT_PROGRESS](#buildkit_progress)                                     | String            | Configure type of progress output.                               |
| [BUILDKIT_TTY_LOG_LINES](#buildkit_tty_log_lines)                           | String            | Number of log lines (for active steps in TTY mode).              |
| [BUILDX_BAKE_GIT_AUTH_HEADER](#buildx_bake_git_auth_header)                 | String            | HTTP authentication scheme for remote Bake files.                |
| [BUILDX_BAKE_GIT_AUTH_TOKEN](#buildx_bake_git_auth_token)                   | String            | HTTP authentication token for remote Bake files.                 |
| [BUILDX_BAKE_GIT_SSH](#buildx_bake_git_ssh)                                 | String            | SSH authentication for remote Bake files.                        |
| [BUILDX_BUILDER](#buildx_builder)                                           | String            | Specify the builder instance to use.                             |
| [BUILDX_CONFIG](#buildx_config)                                             | String            | Specify location for configuration, state, and logs.             |
| [BUILDX_CPU_PROFILE](#buildx_cpu_profile)                                   | String            | Generate a `pprof` CPU profile at the specified location.        |
| [BUILDX_EXPERIMENTAL](#buildx_experimental)                                 | Boolean           | Turn on experimental features.                                   |
| [BUILDX_GIT_CHECK_DIRTY](#buildx_git_check_dirty)                           | Boolean           | Enable dirty Git checkout detection.                             |
| [BUILDX_GIT_INFO](#buildx_git_info)                                         | Boolean           | Remove Git information in provenance attestations.               |
| [BUILDX_GIT_LABELS](#buildx_git_labels)                                     | String \| Boolean | Add Git provenance labels to images.                             |
| [BUILDX_MEM_PROFILE](#buildx_mem_profile)                                   | String            | Generate a `pprof` memory profile at the specified location.     |
| [BUILDX_METADATA_PROVENANCE](#buildx_metadata_provenance)                   | String \| Boolean | Customize provenance informations included in the metadata file. |

Title: Proxy Arguments and Build Tool Configuration Variables

Summary

This section outlines the use of proxy build arguments (`HTTP_PROXY`, `HTTPS_PROXY`, `FTP_PROXY`, `NO_PROXY`, `ALL_PROXY`) for Docker builds, noting they are automatically excluded from the build cache unless explicitly referenced in the Dockerfile. It also details build tool configuration variables for Buildx and BuildKit, clarifying these variables configure the build environment, not the build container itself. A table lists various configuration variables like `BUILDKIT_COLORS`, `BUILDKIT_HOST`, `BUILDX_BUILDER`, enabling adjustments to build behavior and settings.