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| # Dockerfile frontend experimental syntaxes | ||
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| ## Note for Docker users | ||
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| If you are using Docker v18.06 or later, BuildKit mode can be enabled by setting `export DOCKER_BUILDKIT=1` on the client side. | ||
| Docker v18.06 also requires the daemon to be [running in experimental mode](https://docs.docker.com/engine/reference/commandline/dockerd/#description). | ||
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| You need to use `docker build` CLI instead of `buildctl` CLI mentioned in this document. | ||
| See [the `docker build` document](https://docs.docker.com/engine/reference/commandline/build/) for the usage. | ||
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| ## Use experimental Dockerfile frontend | ||
| The features mentioned in this document are experimentally available as [`docker/dockerfile-upstream:experimental`](https://hub.docker.com/r/docker/dockerfile-upstream/tags/) image. | ||
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| To use the experimental features, the first line of your Dockerfile needs to be `# syntax=docker/dockerfile-upstream:experimental`. | ||
| As the experimental syntaxes may change in future revisions, you may want to pin the image to a specific revision. | ||
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| See also [#528](https://github.com/moby/buildkit/issues/528) for further information about planned `docker/dockerfile` releases. | ||
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| ## Experimental syntaxes | ||
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| ### `RUN --mount=type=bind` (the default mount type) | ||
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| This mount type allows binding directories (read-only) in the context or in an image to the build container. | ||
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| |Option |Description| | ||
| |---------------------|-----------| | ||
| |`target` (required) | Mount path.| | ||
| |`source` | Source path in the `from`. Defaults to the root of the `from`.| | ||
| |`from` | Build stage or image name for the root of the source. Defaults to the build context.| | ||
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| ### `RUN --mount=type=cache` | ||
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| This mount type allows the build container to cache directories for compilers and package managers. | ||
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| |Option |Description| | ||
| |---------------------|-----------| | ||
| |`id` | Optional ID to identify separate/different caches| | ||
| |`target` (required) | Mount path.| | ||
| |`ro`,`readonly` | Read-only if set.| | ||
| |`sharing` | One of `shared`, `private`, or `locked`. Defaults to `shared`. A `shared` cache mount can be used concurrently by multiple writers. `private` creates a new mount if there are multiple writers. `locked` pauses the second writer until the first one releases the mount.| | ||
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| #### Example: cache Go packages | ||
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| ```dockerfile | ||
| # syntax = docker/dockerfile-upstream:experimental | ||
| FROM golang | ||
| ... | ||
| RUN --mount=type=cache,target=/root/.cache/go-build go build ... | ||
| ``` | ||
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| #### Example: cache apt packages | ||
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| ```dockerfile | ||
| # syntax = docker/dockerfile-upstream:experimental | ||
| FROM ubuntu | ||
| RUN rm -f /etc/apt/apt.conf.d/docker-clean; echo 'Binary::apt::APT::Keep-Downloaded-Packages "true";' > /etc/apt/apt.conf.d/keep-cache | ||
| RUN --mount=type=cache,target=/var/cache/apt --mount=type=cache,target=/var/lib/apt \ | ||
| apt update && apt install -y gcc | ||
| ``` | ||
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| ### `RUN --mount=type=tmpfs` | ||
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| This mount type allows mounting tmpfs in the build container. | ||
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| |Option |Description| | ||
| |---------------------|-----------| | ||
| |`target` (required) | Mount path.| | ||
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| ### `RUN --mount=type=secret` | ||
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| This mount type allows the build container to access secure files such as private keys without baking them into the image. | ||
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| |Option |Description| | ||
| |---------------------|-----------| | ||
| |`id` | ID of the secret. Defaults to basename of the target path.| | ||
| |`target` | Mount path. Defaults to `/run/secrets/` + `id`.| | ||
| |`required` | If set to `true`, the instruction errors out when the secret is unavailable. Defaults to `false`.| | ||
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| #### Example: access to S3 | ||
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| ```dockerfile | ||
| # syntax = docker/dockerfile-upstream:experimental | ||
| FROM python:3 | ||
| RUN pip install awscli | ||
| RUN --mount=type=secret,id=aws,target=/root/.aws/credentials aws s3 cp s3://... ... | ||
| ``` | ||
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| ```console | ||
| $ buildctl build --frontend=dockerfile.v0 --local context=. --local dockerfile=. \ | ||
| --secret id=aws,src=$HOME/.aws/credentials | ||
| ``` | ||
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| ### `RUN --mount=type=ssh` | ||
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| This mount type allows the build container to access SSH keys via SSH agents, with support for passphrases. | ||
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| |Option |Description| | ||
| |---------------------|-----------| | ||
| |`id` | ID of SSH agent socket or key. Defaults to "default".| | ||
| |`target` | SSH agent socket path. Defaults to `/run/buildkit/ssh_agent.${N}`.| | ||
| |`required` | If set to `true`, the instruction errors out when the key is unavailable. Defaults to `false`.| | ||
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| #### Example: access to Gitlab | ||
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| ```dockerfile | ||
| # syntax = docker/dockerfile-upstream:experimental | ||
| 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 git@gitlab.com | tee /hello | ||
| # "Welcome to GitLab, @GITLAB_USERNAME_ASSOCIATED_WITH_SSHKEY" should be printed here | ||
| ``` | ||
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| ```console | ||
| $ eval $(ssh-agent) | ||
| $ ssh-add ~/.ssh/id_rsa | ||
| (Input your passphrase here) | ||
| $ buildctl build --frontend=dockerfile.v0 --local context=. --local dockerfile=. \ | ||
| --ssh default=$SSH_AUTH_SOCK | ||
| ``` | ||
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| You can also specify a path to `*.pem` file on the host directly instead of `$SSH_AUTH_SOCK`. | ||
| However, pem files with passphrases are not supported. | ||
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