# docker buildx build

# docker buildx build

# docker buildx build

| Description | Start a build |
| --- | --- |
| Usage | docker buildx build [OPTIONS] PATH | URL | - |
| AliasesAn alias is a short or memorable alternative for a longer command. | docker builddocker builder builddocker image builddocker buildx b |

## Description

The `docker buildx build` command starts a build using BuildKit.

## Options

| Option | Default | Description |
| --- | --- | --- |
| --add-host |  | Add a custom host-to-IP mapping (format:host:ip) |
| --allow |  | Allow extra privileged entitlement (e.g.,network.host,security.insecure,device) |
| --annotation |  | Add annotation to the image |
| --attest |  | Attestation parameters (format:type=sbom,generator=image) |
| --build-arg |  | Set build-time variables |
| --build-context |  | Additional build contexts (e.g., name=path) |
| --cache-from |  | External cache sources (e.g.,user/app:cache,type=local,src=path/to/dir) |
| --cache-to |  | Cache export destinations (e.g.,user/app:cache,type=local,dest=path/to/dir) |
| --call | build | Set method for evaluating build (check,outline,targets) |
| --cgroup-parent |  | Set the parent cgroup for theRUNinstructions during build |
| --check |  | Shorthand for--call=check |
| -f, --file |  | Name of the Dockerfile (default:PATH/Dockerfile) |
| --iidfile |  | Write the image ID to a file |
| --label |  | Set metadata for an image |
| --load |  | Shorthand for--output=type=docker |
| --metadata-file |  | Write build result metadata to a file |
| --network |  | Set the networking mode for theRUNinstructions during build |
| --no-cache |  | Do not use cache when building the image |
| --no-cache-filter |  | Do not cache specified stages |
| -o, --output |  | Output destination (format:type=local,dest=path) |
| --platform |  | Set target platform for build |
| --policy |  | Policy configuration (format:filename=path[,filename=path][,reset=true|false][,disabled=true|false][,strict=true|false][,log-level=level]) |
| --progress | auto | Set type of progress output (auto,none,plain,quiet,rawjson,tty). Use plain to show container output |
| --provenance |  | Shorthand for--attest=type=provenance |
| --pull |  | Always attempt to pull all referenced images |
| --push |  | Shorthand for--output=type=registry,unpack=false |
| -q, --quiet |  | Suppress the build output and print image ID on success |
| --sbom |  | Shorthand for--attest=type=sbom |
| --secret |  | Secret to expose to the build (format:id=mysecret[,src=/local/secret]) |
| --shm-size |  | Shared memory size for build containers |
| --ssh |  | SSH agent socket or keys to expose to the build (format:default|<id>[=<socket>|<key>[,<key>]]) |
| -t, --tag |  | Image identifier (format:[registry/]repository[:tag]) |
| --target |  | Set the target build stage to build |
| --ulimit |  | Ulimit options |

## Examples

### Add entries to container hosts file (--add-host)

You can add other hosts into a build container's `/etc/hosts` file by using one
or more `--add-host` flags. This example adds static addresses for hosts named
`my-hostname` and `my_hostname_v6`:

```console
$ docker buildx build --add-host my_hostname=8.8.8.8 --add-host my_hostname_v6=2001:4860:4860::8888 .
```

If you need your build to connect to services running on the host, you can use
the special `host-gateway` value for `--add-host`. In the following example,
build containers resolve `host.docker.internal` to the host's gateway IP.

```console
$ docker buildx build --add-host host.docker.internal=host-gateway .
```

You can wrap an IPv6 address in square brackets.
`=` and `:` are both valid separators.
Both formats in the following example are valid:

```console
$ docker buildx build --add-host my-hostname:10.180.0.1 --add-host my-hostname_v6=[2001:4860:4860::8888] .
```

### Create annotations (--annotation)

```text
--annotation="key=value"
--annotation="[type:]key=value"
```

Add OCI annotations to the image index, manifest, or descriptor.
The following example adds the `foo=bar` annotation to the image manifests:

```console
$ docker buildx build -t TAG --annotation "foo=bar" --push .
```

You can optionally add a type prefix to specify the level of the annotation. By
default, the image manifest is annotated. The following example adds the
`foo=bar` annotation the image index instead of the manifests:

```console
$ docker buildx build -t TAG --annotation "index:foo=bar" --push .
```

You can specify multiple types, separated by a comma (,) to add the annotation
to multiple image components. The following example adds the `foo=bar`
annotation to image index, descriptors, manifests:

```console
$ docker buildx build -t TAG --annotation "index,manifest,manifest-descriptor:foo=bar" --push .
```

You can also specify a platform qualifier in square brackets (`[os/arch]`) in
the type prefix, to apply the annotation to a subset of manifests with the
matching platform. The following example adds the `foo=bar` annotation only to
the manifest with the `linux/amd64` platform:

```console
$ docker buildx build -t TAG --annotation "manifest[linux/amd64]:foo=bar" --push .
```

Wildcards are not supported in the platform qualifier; you can't specify a type
prefix like `manifest[linux/*]` to add annotations only to manifests which has
`linux` as the OS platform.

For more information about annotations, see
[Annotations](https://docs.docker.com/build/building/annotations/).

### Create attestations (--attest)

```text
--attest=type=sbom,...
--attest=type=provenance,...
```

Create
[image attestations](https://docs.docker.com/build/metadata/attestations/).
BuildKit currently supports:

- `sbom` - Software Bill of Materials.
  Use `--attest=type=sbom` to generate an SBOM for an image at build-time.
  Alternatively, you can use the [--sbomshorthand](#sbom).
  For more information, see
  [here](https://docs.docker.com/build/metadata/attestations/sbom/).
- `provenance` - SLSA Provenance
  Use `--attest=type=provenance` to generate provenance for an image at
  build-time. Alternatively, you can use the [--provenanceshorthand](#provenance).
  By default, a minimal provenance attestation will be created for the build
  result, which will only be attached for images pushed to registries.
  For more information, see
  [here](https://docs.docker.com/build/metadata/attestations/slsa-provenance/).

### Allow extra privileged entitlement (--allow)

```text
--allow=ENTITLEMENT
```

Allow extra privileged entitlement. List of entitlements:

- `network.host` - Allows executions with host networking.
- `security.insecure` - Allows executions without sandbox. See
  [related Dockerfile extensions](https://docs.docker.com/reference/dockerfile/#run---security).
- `device` - Allows access to Container Device Interface (CDI) devices.
  - `--allow device` - Grants access to all devices.
  - `--allow device=kind|name` - Grants access to a specific device.
  - `--allow device=kind|name,alias=kind|name` - Grants access to a specific device, with optional aliasing.

For entitlements to be enabled, the BuildKit daemon also needs to allow them
with `--allow-insecure-entitlement` (see
[create --buildkitd-flags](https://docs.docker.com/reference/cli/docker/buildx/create/#buildkitd-flags)).

```console
$ docker buildx create --use --name insecure-builder --buildkitd-flags '--allow-insecure-entitlement security.insecure'
$ docker buildx build --allow security.insecure .
```

### Set build-time variables (--build-arg)

You can use `ENV` instructions in a Dockerfile to define variable values. These
values persist in the built image. Often persistence isn't what you want. Users
want to specify variables differently depending on which host they build an
image on.

A good example is `http_proxy` or source versions for pulling intermediate
files. The `ARG` instruction lets Dockerfile authors define values that users
can set at build-time using the `--build-arg` flag:

```console
$ docker buildx build --build-arg HTTP_PROXY=http://10.20.30.2:1234 --build-arg FTP_PROXY=http://40.50.60.5:4567 .
```

This flag allows you to pass the build-time variables that are
accessed like regular environment variables in the `RUN` instruction of the
Dockerfile. These values don't persist in the intermediate or final images
like `ENV` values do. You must add `--build-arg` for each build argument.

Using this flag doesn't alter the output you see when the build process echoes the`ARG` lines from the
Dockerfile.

For detailed information on using `ARG` and `ENV` instructions, see the
[Dockerfile reference](https://docs.docker.com/reference/dockerfile/).

You can also use the `--build-arg` flag without a value, in which case the daemon
propagates the value from the local environment into the Docker container it's building:

```console
$ export HTTP_PROXY=http://10.20.30.2:1234
$ docker buildx build --build-arg HTTP_PROXY .
```

This example is similar to how `docker run -e` works. Refer to the
[docker rundocumentation](https://docs.docker.com/reference/cli/docker/container/run/#env)
for more information.

There are also useful built-in build arguments, such as:

- `BUILDKIT_CONTEXT_KEEP_GIT_DIR=<bool>`: trigger git context to keep the `.git` directory
- `BUILDKIT_INLINE_CACHE=<bool>`: inline cache metadata to image config or not
- `BUILDKIT_MULTI_PLATFORM=<bool>`: opt into deterministic output regardless of multi-platform output or not

```console
$ docker buildx build --build-arg BUILDKIT_MULTI_PLATFORM=1 .
```

Learn more about the built-in build arguments in the
[Dockerfile reference docs](https://docs.docker.com/reference/dockerfile/#buildkit-built-in-build-args).

### Additional build contexts (--build-context)

```text
--build-context=name=VALUE
```

Define additional build context with specified contents.

In a Dockerfile:

- the context can be accessed when `FROM name` or `--from=name` is used
- the context overrides a stage called `name` when used as `FROM ... AS name`
- the context overrides a `#syntax` directive when used as `#syntax=name`

The value can be a:

- local source directory
- [local OCI layout compliant directory](https://github.com/opencontainers/image-spec/blob/main/image-layout.md)
- container image
- Git URL
- HTTP URL

#### Use a local path

Expose a secondary local source directory:

```console
$ docker buildx build --build-context project=path/to/project/source .
# docker buildx build --build-context project=https://github.com/myuser/project.git .
```

#### Use a container image

Use the `docker-image://` scheme.

Replace `alpine:latest` with a pinned one:

```console
$ docker buildx build --build-context alpine=docker-image://alpine@sha256:0123456789 .
```

```dockerfile
# syntax=docker/dockerfile:1
FROM alpine
COPY --from=project myfile /
```

#### Use an OCI layout directory as build context

Use the `oci-layout:///` scheme.

Source an image from a local
[OCI layout compliant directory](https://github.com/opencontainers/image-spec/blob/main/image-layout.md),
either by tag, or by digest:

```console
$ docker buildx build --build-context foo=oci-layout:///path/to/local/layout:<tag>
$ docker buildx build --build-context foo=oci-layout:///path/to/local/layout@sha256:<digest>
```

```dockerfile
# syntax=docker/dockerfile:1
FROM alpine
RUN apk add git
COPY --from=foo myfile /

FROM foo
```

The OCI layout directory must be compliant with the [OCI layout specification](https://github.com/opencontainers/image-spec/blob/main/image-layout.md).

### Override the configured builder instance (--builder)

Same as
[buildx --builder](https://docs.docker.com/reference/cli/docker/buildx/#builder).

### Use an external cache source for a build (--cache-from)

```text
--cache-from=[NAME|type=TYPE[,KEY=VALUE]]
```

Use an external cache source for a build. Supported types are:

- [registry](https://docs.docker.com/build/cache/backends/registry/)
  can import cache from a cache manifest or (special) image configuration on the
  registry.
- [local](https://docs.docker.com/build/cache/backends/local/) can
  import cache from local files previously exported with `--cache-to`.
- [gha](https://docs.docker.com/build/cache/backends/gha/)
  can import cache from a previously exported cache with `--cache-to` in your
  GitHub repository.
- [s3](https://docs.docker.com/build/cache/backends/s3/)
  can import cache from a previously exported cache with `--cache-to` in your
  S3 bucket.
- [azblob](https://docs.docker.com/build/cache/backends/azblob/)
  can import cache from a previously exported cache with `--cache-to` in your
  Azure bucket.

If no type is specified, `registry` exporter is used with a specified reference.

```console
$ docker buildx build --cache-from=user/app:cache .
$ docker buildx build --cache-from=user/app .
$ docker buildx build --cache-from=type=registry,ref=user/app .
$ docker buildx build --cache-from=type=local,src=path/to/cache .
$ docker buildx build --cache-from=type=gha .
$ docker buildx build --cache-from=type=s3,region=eu-west-1,bucket=mybucket .
```

> Note
>
> More info about cache exporters and available attributes can be found in the
> [Cache storage backends documentation](https://docs.docker.com/build/cache/backends/)

### Export build cache to an external cache destination (--cache-to)

```text
--cache-to=[NAME|type=TYPE[,KEY=VALUE]]
```

Export build cache to an external cache destination. Supported types are:

- [registry](https://docs.docker.com/build/cache/backends/registry/) exports
  build cache to a cache manifest in the registry.
- [local](https://docs.docker.com/build/cache/backends/local/) exports
  cache to a local directory on the client.
- [inline](https://docs.docker.com/build/cache/backends/inline/) writes the
  cache metadata into the image configuration.
- [gha](https://docs.docker.com/build/cache/backends/gha/) exports cache
  through the GitHub Actions Cache service API.
- [s3](https://docs.docker.com/build/cache/backends/s3/) exports cache to a
  S3 bucket.
- [azblob](https://docs.docker.com/build/cache/backends/azblob/) exports
  cache to an Azure bucket.

```console
$ docker buildx build --cache-to=user/app:cache .
$ docker buildx build --cache-to=type=inline .
$ docker buildx build --cache-to=type=registry,ref=user/app .
$ docker buildx build --cache-to=type=local,dest=path/to/cache .
$ docker buildx build --cache-to=type=gha .
$ docker buildx build --cache-to=type=s3,region=eu-west-1,bucket=mybucket .
```

> Note
>
> More info about cache exporters and available attributes can be found in the
> [Cache storage backends documentation](https://docs.docker.com/build/cache/backends/)

### Invoke a frontend method (--call)

```text
--call=[build|check|outline|targets]
```

BuildKit frontends can support alternative modes of executions for builds,
using frontend methods. Frontend methods are a way to change or extend the
behavior of a build invocation, which lets you, for example, inspect, validate,
or generate alternative outputs from a build.

The `--call` flag for `docker buildx build` lets you specify the frontend
method that you want to execute. If this flag is unspecified, it defaults to
executing the build and evaluating
[build checks](https://docs.docker.com/reference/build-checks/).

For Dockerfiles, the available methods are:

| Command | Description |
| --- | --- |
| build(default) | Execute the build and evaluate build checks for the current build target. |
| check | Evaluate build checks for the either the entire Dockerfile or the selected target, without executing a build. |
| outline | Show the build arguments that you can set for a target, and their default values. |
| targets | List all the build targets in the Dockerfile. |
| subrequests.describe | List all the frontend methods that the current frontend supports. |

Note that other frontends may implement these or other methods.
To see the list of available methods for the frontend you're using,
use `--call=subrequests.describe`.

```console
$ docker buildx build -q --call=subrequests.describe .

NAME                 VERSION DESCRIPTION
outline              1.0.0   List all parameters current build target supports
targets              1.0.0   List all targets current build supports
subrequests.describe 1.0.0   List available subrequest types
```

#### Descriptions

The [--call=targets](#call-targets) and [--call=outline](#call-outline)
methods include descriptions for build targets and arguments, if available.
Descriptions are generated from comments in the Dockerfile. A comment on the
line before a `FROM` instruction becomes the description of a build target, and
a comment before an `ARG` instruction the description of a build argument. The
comment must lead with the name of the stage or argument, for example:

```dockerfile
# syntax=docker/dockerfile:1

# GO_VERSION sets the Go version for the build
ARG GO_VERSION=1.22

# base-builder is the base stage for building the project
FROM golang:${GO_VERSION} AS base-builder
```

When you run `docker buildx build --call=outline`, the output includes the
descriptions, as follows:

```console
$ docker buildx build -q --call=outline .

TARGET:      base-builder
DESCRIPTION: is the base stage for building the project

BUILD ARG    VALUE   DESCRIPTION
GO_VERSION   1.22    sets the Go version for the build
```

For more examples on how to write Dockerfile docstrings,
check out [the Dockerfile for Docker docs](https://github.com/docker/docs/blob/main/Dockerfile).

#### Call: check (--check)

The `check` method evaluates build checks without executing the build. The
`--check` flag is a convenient shorthand for `--call=check`. Use the `check`
method to validate the build configuration before starting the build.

```console
$ docker buildx build -q --check https://github.com/docker/docs.git

WARNING: InvalidBaseImagePlatform
Base image wjdp/htmltest:v0.17.0 was pulled with platform "linux/amd64", expected "linux/arm64" for current build
Dockerfile:43
--------------------
  41 |         "#content/desktop/previous-versions/*.md"
  42 |
  43 | >>> FROM wjdp/htmltest:v${HTMLTEST_VERSION} AS test
  44 |     WORKDIR /test
  45 |     COPY --from=build /out ./public
--------------------
```

Using `--check` without specifying a target evaluates the entire Dockerfile.
If you want to evaluate a specific target, use the `--target` flag.

#### Call: outline

The `outline` method prints the name of the specified target (or the default
target, if `--target` isn't specified), and the build arguments that the target
consumes, along with their default values, if set.

The following example shows the default target `release` and its build arguments:

```console
$ docker buildx build -q --call=outline https://github.com/docker/docs.git

TARGET:      release
DESCRIPTION: is an empty scratch image with only compiled assets

BUILD ARG          VALUE     DESCRIPTION
GO_VERSION         1.22      sets the Go version for the base stage
HUGO_VERSION       0.127.0
HUGO_ENV                     sets the hugo.Environment (production, development, preview)
DOCS_URL                     sets the base URL for the site
PAGEFIND_VERSION   1.1.0
```

This means that the `release` target is configurable using these build arguments:

```console
$ docker buildx build \
  --build-arg GO_VERSION=1.22 \
  --build-arg HUGO_VERSION=0.127.0 \
  --build-arg HUGO_ENV=production \
  --build-arg DOCS_URL=https://example.com \
  --build-arg PAGEFIND_VERSION=1.1.0 \
  --target release https://github.com/docker/docs.git
```

#### Call: targets

The `targets` method lists all the build targets in the Dockerfile. These are
the stages that you can build using the `--target` flag. It also indicates the
default target, which is the target that will be built when you don't specify a
target.

```console
$ docker buildx build -q --call=targets https://github.com/docker/docs.git

TARGET            DESCRIPTION
base              is the base stage with build dependencies
node              installs Node.js dependencies
hugo              downloads and extracts the Hugo binary
build-base        is the base stage for building the site
dev               is for local development with Docker Compose
build             creates production builds with Hugo
lint              lints markdown files
test              validates HTML output and checks for broken links
update-modules    downloads and vendors Hugo modules
vendor            is an empty stage with only vendored Hugo modules
build-upstream    builds an upstream project with a replacement module
validate-upstream validates HTML output for upstream builds
unused-media      checks for unused graphics and other media
pagefind          installs the Pagefind runtime
index             generates a Pagefind index
test-go-redirects checks that the /go/ redirects are valid
release (default) is an empty scratch image with only compiled assets
```

### Use a custom parent cgroup (--cgroup-parent)

When you run `docker buildx build` with the `--cgroup-parent` option,
the daemon runs the containers used in the build with the
[correspondingdocker runflag](https://docs.docker.com/reference/cli/docker/container/run/#cgroup-parent).

### Specify a Dockerfile (-f, --file)

```console
$ docker buildx build -f <filepath> .
```

Specifies the filepath of the Dockerfile to use.
If unspecified, a file named `Dockerfile` at the root of the build context is used by default.

To read a Dockerfile from stdin, you can use `-` as the argument for `--file`.

```console
$ cat Dockerfile | docker buildx build -f - .
```

### Load the single-platform build result todocker images(--load)

Shorthand for [--output=type=docker](#docker). Will automatically load the
single-platform build result to `docker images`.

### Write build result metadata to a file (--metadata-file)

To output build metadata such as the image digest, pass the `--metadata-file` flag.
The metadata will be written as a JSON object to the specified file. The
directory of the specified file must already exist and be writable.

```console
$ docker buildx build --load --metadata-file metadata.json .
$ cat metadata.json
```

```json
{
  "buildx.build.provenance": {},
  "buildx.build.ref": "mybuilder/mybuilder0/0fjb6ubs52xx3vygf6fgdl611",
  "buildx.build.warnings": {},
  "containerimage.config.digest": "sha256:2937f66a9722f7f4a2df583de2f8cb97fc9196059a410e7f00072fc918930e66",
  "containerimage.descriptor": {
    "annotations": {
      "config.digest": "sha256:2937f66a9722f7f4a2df583de2f8cb97fc9196059a410e7f00072fc918930e66",
      "org.opencontainers.image.created": "2022-02-08T21:28:03Z"
    },
    "digest": "sha256:19ffeab6f8bc9293ac2c3fdf94ebe28396254c993aea0b5a542cfb02e0883fa3",
    "mediaType": "application/vnd.oci.image.manifest.v1+json",
    "size": 506
  },
  "containerimage.digest": "sha256:19ffeab6f8bc9293ac2c3fdf94ebe28396254c993aea0b5a542cfb02e0883fa3"
}
```

> Note
>
> Build record
> [provenance](https://docs.docker.com/build/metadata/attestations/slsa-provenance/#provenance-attestation-example)
> (`buildx.build.provenance`) includes minimal provenance by default. Set the
> `BUILDX_METADATA_PROVENANCE` environment variable to customize this behavior:
>
>
>
> - `min` sets minimal provenance (default).
> - `max` sets full provenance.
> - `disabled`, `false` or `0` doesn't set any provenance.

> Note
>
> Build warnings (`buildx.build.warnings`) are not included by default. Set the
> `BUILDX_METADATA_WARNINGS` environment variable to `1` or `true` to
> include them.

### Set the networking mode for the RUN instructions during build (--network)

Available options for the networking mode are:

- `default` (default): Run in the default network.
- `none`: Run with no network access.
- `host`: Run in the host’s network environment.

Find more details in the
[Dockerfile reference](https://docs.docker.com/reference/dockerfile/#run---network).

### Ignore build cache for specific stages (--no-cache-filter)

The `--no-cache-filter` lets you specify one or more stages of a multi-stage
Dockerfile for which build cache should be ignored. To specify multiple stages,
use a comma-separated syntax:

```console
$ docker buildx build --no-cache-filter stage1,stage2,stage3 .
```

For example, the following Dockerfile contains four stages:

- `base`
- `install`
- `test`
- `release`

```dockerfile
# syntax=docker/dockerfile:1

FROM oven/bun:1 AS base
WORKDIR /app

FROM base AS install
WORKDIR /temp/dev
RUN --mount=type=bind,source=package.json,target=package.json \
    --mount=type=bind,source=bun.lockb,target=bun.lockb \
    bun install --frozen-lockfile

FROM base AS test
COPY --from=install /temp/dev/node_modules node_modules
COPY . .
RUN bun test

FROM base AS release
ENV NODE_ENV=production
COPY --from=install /temp/dev/node_modules node_modules
COPY . .
ENTRYPOINT ["bun", "run", "index.js"]
```

To ignore the cache for the `install` stage:

```console
$ docker buildx build --no-cache-filter install .
```

To ignore the cache the `install` and `release` stages:

```console
$ docker buildx build --no-cache-filter install,release .
```

The arguments for the `--no-cache-filter` flag must be names of stages.

### Set the export action for the build result (-o, --output)

```text
-o, --output=[PATH,-,type=TYPE[,KEY=VALUE]
```

Sets the export action for the build result. The default output, when using the
`docker` [build driver](https://docs.docker.com/build/builders/drivers/), is a container
image exported to the local image store. The `--output` flag makes this step
configurable allows export of results directly to the client's filesystem, an
OCI image tarball, a registry, and more.

Buildx with `docker` driver only supports the local, tarball, and image
[exporters](https://docs.docker.com/build/exporters/). The `docker-container`
driver supports all exporters.

If you only specify a filepath as the argument to `--output`, Buildx uses the
local exporter. If the value is `-`, Buildx uses the `tar` exporter and writes
the output to stdout.

```console
$ docker buildx build -o . .
$ docker buildx build -o outdir .
$ docker buildx build -o - . > out.tar
$ docker buildx build -o type=docker .
$ docker buildx build -o type=docker,dest=- . > myimage.tar
$ docker buildx build -t tonistiigi/foo -o type=registry
```

You can export multiple outputs by repeating the flag.

Supported exported types are:

- [local](#local)
- [tar](#tar)
- [oci](#oci)
- [docker](#docker)
- [image](#image)
- [registry](#registry)

#### local

The `local` export type writes all result files to a directory on the client. The
new files will be owned by the current user. On multi-platform builds, all results
will be put in subdirectories by their platform.

Attribute key:

- `dest` - destination directory where files will be written

For more information, see
[Local and tar exporters](https://docs.docker.com/build/exporters/local-tar/).

#### tar

The `tar` export type writes all result files as a single tarball on the client.
On multi-platform builds all results will be put in subdirectories by their platform.

Attribute key:

- `dest` - destination path where tarball will be written. “-” writes to stdout.

For more information, see
[Local and tar exporters](https://docs.docker.com/build/exporters/local-tar/).

#### oci

The `oci` export type writes the result image or manifest list as an [OCI image
layout](https://github.com/opencontainers/image-spec/blob/v1.0.1/image-layout.md)
tarball on the client.

Attribute key:

- `dest` - destination path where tarball will be written. “-” writes to stdout.

For more information, see
[OCI and Docker exporters](https://docs.docker.com/build/exporters/oci-docker/).

#### docker

The `docker` export type writes the single-platform result image as a [Docker image
specification](https://github.com/docker/docker/blob/v20.10.2/image/spec/v1.2.md)
tarball on the client. Tarballs created by this exporter are also OCI compatible.

The default image store in Docker Engine doesn't support loading multi-platform
images. You can enable the containerd image store, or push multi-platform images
is to directly push to a registry, see [registry](#registry).

Attribute keys:

- `dest` - destination path where tarball will be written. If not specified,
  the tar will be loaded automatically to the local image store.
- `context` - name for the Docker context where to import the result

For more information, see
[OCI and Docker exporters](https://docs.docker.com/build/exporters/oci-docker/).

#### image

The `image` exporter writes the build result as an image or a manifest list. When
using `docker` driver the image will appear in `docker images`. Optionally, image
can be automatically pushed to a registry by specifying attributes.

Attribute keys:

- `name` - name (references) for the new image.
- `push` - Boolean to automatically push the image.

For more information, see
[Image and registry exporters](https://docs.docker.com/build/exporters/image-registry/).

#### registry

The `registry` exporter is a shortcut for `type=image,push=true`.

For more information, see
[Image and registry exporters](https://docs.docker.com/build/exporters/image-registry/).

### Set the target platforms for the build (--platform)

```text
--platform=value[,value]
```

Set the target platform for the build. All `FROM` commands inside the Dockerfile
without their own `--platform` flag will pull base images for this platform and
this value will also be the platform of the resulting image.

The default value is the platform of the BuildKit daemon where the build runs.
The value takes the form of `os/arch` or `os/arch/variant`. For example,
`linux/amd64` or `linux/arm/v7`. Additionally, the `--platform` flag also supports
a special `local` value, which tells BuildKit to use the platform of the BuildKit
client that invokes the build.

When using `docker-container` driver with `buildx`, this flag can accept multiple
values as an input separated by a comma. With multiple values the result will be
built for all of the specified platforms and joined together into a single manifest
list.

If the `Dockerfile` needs to invoke the `RUN` command, the builder needs runtime
support for the specified platform. In a clean setup, you can only execute `RUN`
commands for your system architecture.
If your kernel supports [binfmt_misc](https://en.wikipedia.org/wiki/Binfmt_misc)
launchers for secondary architectures, buildx will pick them up automatically.
Docker Desktop releases come with `binfmt_misc` automatically configured for `arm64`
and `arm` architectures. You can see what runtime platforms your current builder
instance supports by running `docker buildx inspect --bootstrap`.

Inside a `Dockerfile`, you can access the current platform value through
`TARGETPLATFORM` build argument. Refer to the
[Dockerfile reference](https://docs.docker.com/reference/dockerfile/#automatic-platform-args-in-the-global-scope)
for the full description of automatic platform argument variants .

You can find the formatting definition for the platform specifier in the
[containerd source code](https://github.com/containerd/containerd/blob/v1.4.3/platforms/platforms.go#L63).

```console
$ docker buildx build --platform=linux/arm64 .
$ docker buildx build --platform=linux/amd64,linux/arm64,linux/arm/v7 .
$ docker buildx build --platform=darwin .
```

### Set type of progress output (--progress)

```text
--progress=VALUE
```

Set type of progress output. Supported values are:

- `auto` (default): Uses the `tty` mode if the client is a TTY, or `plain` otherwise
- `tty`: An interactive stream of the output with color and redrawing
- `plain`: Prints the raw build progress in a plaintext format
- `quiet`: Suppress the build output and print image ID on success (same as `--quiet`)
- `rawjson`: Prints the raw build progress as JSON lines

> Note
>
> You can also use the `BUILDKIT_PROGRESS` environment variable to set its value.

The following example uses `plain` output during the build:

```console
$ docker buildx build --load --progress=plain .

#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 227B 0.0s done
#1 DONE 0.1s

#2 [internal] load .dockerignore
#2 transferring context: 129B 0.0s done
#2 DONE 0.0s
...
```

> Note
>
> Check also the
> [BUILDKIT_COLORS](https://docs.docker.com/build/building/variables/#buildkit_colors)
> environment variable for modifying the colors of the terminal output.

The `rawjson` output marshals the solve status events from BuildKit to JSON lines.
This mode is designed to be read by an external program.

### Create provenance attestations (--provenance)

Shorthand for [--attest=type=provenance](#attest), used to configure
provenance attestations for the build result. For example,
`--provenance=mode=max` can be used as an abbreviation for
`--attest=type=provenance,mode=max`.

Additionally, `--provenance` can be used with Boolean values to enable or disable
provenance attestations. For example, `--provenance=false` disables all provenance attestations,
while `--provenance=true` enables all provenance attestations.

By default, a minimal provenance attestation will be created for the build
result. Note that the default image store in Docker Engine doesn't support
attestations. Provenance attestations only persist for images pushed directly
to a registry if you use the default image store. Alternatively, you can switch
to using the containerd image store.

For more information about provenance attestations, see
[here](https://docs.docker.com/build/metadata/attestations/slsa-provenance/).

### Push the build result to a registry (--push)

Shorthand for [--output=type=registry](#registry). Will automatically push the
build result to registry.

### Create SBOM attestations (--sbom)

Shorthand for [--attest=type=sbom](#attest), used to configure SBOM
attestations for the build result. For example,
`--sbom=generator=<user>/<generator-image>` can be used as an abbreviation for
`--attest=type=sbom,generator=<user>/<generator-image>`.

Additionally, `--sbom` can be used with Boolean values to enable or disable
SBOM attestations. For example, `--sbom=false` disables all SBOM attestations.

Note that the default image store in Docker Engine doesn't support
attestations. Provenance attestations only persist for images pushed directly
to a registry if you use the default image store. Alternatively, you can switch
to using the containerd image store.

For more information, see
[here](https://docs.docker.com/build/metadata/attestations/sbom/).

### Secret to expose to the build (--secret)

```text
--secret=[type=TYPE[,KEY=VALUE]
```

Exposes secrets (authentication credentials, tokens) to the build.
A secret can be mounted into the build using a `RUN --mount=type=secret` mount in the
[Dockerfile](https://docs.docker.com/reference/dockerfile/#run---mounttypesecret).
For more information about how to use build secrets, see
[Build secrets](https://docs.docker.com/build/building/secrets/).

Supported types are:

- [type=file](#typefile)
- [type=env](#typeenv)

Buildx attempts to detect the `type` automatically if unset. If an environment
variable with the same key as `id` is set, then Buildx uses `type=env` and the
variable value becomes the secret. If no such environment variable is set, and
`type` is not set, then Buildx falls back to `type=file`.

#### type=file

Source a build secret from a file.

##### type=filesynopsis

```console
$ docker buildx build --secret [type=file,]id=ID[,src=FILEPATH] .
```

##### type=fileattributes

| Key | Description | Default |
| --- | --- | --- |
| id | ID of the secret. | N/A (this key is required) |
| src,source | Filepath of the file containing the secret value (absolute or relative to current working directory). | idif unset. |

###### type=fileusage

In the following example, `type=file` is automatically detected because no
environment variable matching `aws` (the ID) is set.

```console
$ docker buildx build --secret id=aws,src=$HOME/.aws/credentials .
```

```dockerfile
# syntax=docker/dockerfile:1
FROM python:3
RUN pip install awscli
RUN --mount=type=secret,id=aws,target=/root/.aws/credentials \
  aws s3 cp s3://... ...
```

#### type=env

Source a build secret from an environment variable.

##### type=envsynopsis

```console
$ docker buildx build --secret [type=env,]id=ID[,env=VARIABLE] .
```

##### type=envattributes

| Key | Description | Default |
| --- | --- | --- |
| id | ID of the secret. | N/A (this key is required) |
| env,src,source | Environment variable to source the secret from. | idif unset. |

##### type=envusage

In the following example, `type=env` is automatically detected because an
environment variable matching `id` is set.

```console
$ SECRET_TOKEN=token docker buildx build --secret id=SECRET_TOKEN .
```

```dockerfile
# syntax=docker/dockerfile:1
FROM node:alpine
RUN --mount=type=bind,target=. \
  --mount=type=secret,id=SECRET_TOKEN,env=SECRET_TOKEN \
  yarn run test
```

In the following example, the build argument `SECRET_TOKEN` is set to contain
the value of the environment variable `API_KEY`.

```console
$ API_KEY=token docker buildx build --secret id=SECRET_TOKEN,env=API_KEY .
```

You can also specify the name of the environment variable with `src` or `source`:

```console
$ API_KEY=token docker buildx build --secret type=env,id=SECRET_TOKEN,src=API_KEY .
```

> Note
>
> Specifying the environment variable name with `src` or `source`, you are
> required to set `type=env` explicitly, or else Buildx assumes that the secret
> is `type=file`, and looks for a file with the name of `src` or `source` (in
> this case, a file named `API_KEY` relative to the location where the `docker buildx build` command was executed.

### Shared memory size for build containers (--shm-size)

Sets the size of the shared memory allocated for build containers when using
`RUN` instructions.

The format is `<number><unit>`. `number` must be greater than `0`. Unit is
optional and can be `b` (bytes), `k` (kilobytes), `m` (megabytes), or `g`
(gigabytes). If you omit the unit, the system uses bytes.

> Note
>
> In most cases, it is recommended to let the builder automatically determine
> the appropriate configurations. Manual adjustments should only be considered
> when specific performance tuning is required for complex build scenarios.

### SSH agent socket or keys to expose to the build (--ssh)

```text
--ssh=default|<id>[=<socket>|<key>[,<key>]]
```

This can be useful when some commands in your Dockerfile need specific SSH
authentication (e.g., cloning a private repository).

`--ssh` exposes SSH agent socket or keys to the build and can be used with the
[RUN --mount=type=sshmount](https://docs.docker.com/reference/dockerfile/#run---mounttypessh).

Example to access Gitlab using an SSH agent socket:

```dockerfile
# syntax=docker/dockerfile:1
FROM alpine
RUN apk add --no-cache openssh-client
RUN mkdir -p -m 0700 ~/.ssh && ssh-keyscan gitlab.com >> ~/.ssh/known_hosts
RUN --mount=type=ssh ssh -q -T git@gitlab.com 2>&1 | tee /hello
# "Welcome to GitLab, @GITLAB_USERNAME_ASSOCIATED_WITH_SSHKEY" should be printed here
# with the type of build progress is defined as `plain`.
```

```console
$ eval $(ssh-agent)
$ ssh-add ~/.ssh/id_rsa
(Input your passphrase here)
$ docker buildx build --ssh default=$SSH_AUTH_SOCK .
```

### Tag an image (-t, --tag)

```console
$ docker buildx build -t docker/apache:2.0 .
```

This examples builds in the same way as the previous example, but it then tags the resulting
image. The repository name will be `docker/apache` and the tag `2.0`.

[Read more about valid tags](https://docs.docker.com/reference/cli/docker/image/tag/).

You can apply multiple tags to an image. For example, you can apply the `latest`
tag to a newly built image and add another tag that references a specific
version.

For example, to tag an image both as `docker/fedora-jboss:latest` and
`docker/fedora-jboss:v2.1`, use the following:

```console
$ docker buildx build -t docker/fedora-jboss:latest -t docker/fedora-jboss:v2.1 .
```

### Specifying target build stage (--target)

When building a Dockerfile with multiple build stages, use the `--target`
option to specify an intermediate build stage by name as a final stage for the
resulting image. The builder skips commands after the target stage.

```dockerfile
FROM debian AS build-env
# ...

FROM alpine AS production-env
# ...
```

```console
$ docker buildx build -t mybuildimage --target build-env .
```

### Set ulimits (--ulimit)

`--ulimit` overrides the default ulimits of build's containers when using `RUN`
instructions and are specified with a soft and hard limit as such:
`<type>=<soft limit>[:<hard limit>]`, for example:

```console
$ docker buildx build --ulimit nofile=1024:1024 .
```

> Note
>
> If you don't provide a `hard limit`, the `soft limit` is used
> for both values. If no `ulimits` are set, they're inherited from
> the default `ulimits` set on the daemon.

> Note
>
> In most cases, it is recommended to let the builder automatically determine
> the appropriate configurations. Manual adjustments should only be considered
> when specific performance tuning is required for complex build scenarios.
