An example Docker multi-platform builds.
Each repo can specify multiple architectures for any and all tags. If no architecture is specified, images are built in Linux on amd64 (aka x86-64). To specify more or different architectures, use the Architectures field (comma-delimited list, whitespace is trimmed). Valid architectures are found in Bashbrew's oci-platform.go file:
amd64arm32v6arm32v7arm64v8i386mips64leppc64leriscv64s390xwindows-amd64
The Architectures of any given tag must be a strict subset of the Architectures of the tag it is FROM.
Images must have a single Dockerfile per entry in the library file that can be used for multiple architectures. This means that each supported architecture will have the same FROM line (e.g. FROM debian:buster). See golang, docker, haproxy, and php for examples of library files using one Dockerfile per entry and see their respective git repos for example Dockerfiles.
If different parts of the Dockerfile only happen in one architecture or another, use control flow (e.g.if/case) along with dpkg --print-architecture or apk -print-arch to detect the userspace architecture. Only use uname for architecture detection when more accurate tools cannot be installed. See golang for an example where some architectures require building binaries from the upstream source packages and some merely download the binary release.
For base images like debian it will be necessary to have a different Dockerfile and build context in order to ADD architecture specific binaries and this is a valid exception to the above. Since these images use the same Tags, they need to be in the same entry. Use the architecture specific fields for GitRepo, GitFetch, GitCommit, and Directory, which are the architecture concatenated with hyphen (-) and the field (e.g. arm32v7-GitCommit). Any architecture that does not have an architecture-specific field will use the default field (e.g. no arm32v7-Directory means Directory will be used for arm32v7). See the debian or ubuntu files in the library for examples. The following is an example for hello-world:
Maintainers: Tianon Gravi <[email protected]> (@tianon),
Joseph Ferguson <[email protected]> (@yosifkit)
GitRepo: https://github.com/docker-library/hello-world.git
GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
Tags: latest
Architectures: amd64, arm32v5, arm32v7, arm64v8, ppc64le, s390x
# all the same commit; easy for us to generate this way since they could be different
amd64-GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
amd64-Directory: amd64/hello-world
arm32v5-GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
arm32v5-Directory: arm32v5/hello-world
arm32v7-GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
arm32v7-Directory: arm32v7/hello-world
arm64v8-GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
arm64v8-Directory: arm64v8/hello-world
ppc64le-GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
ppc64le-Directory: ppc64le/hello-world
s390x-GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
s390x-Directory: s390x/hello-world
Tags: nanoserver
Architectures: windows-amd64
# if there is only one architecture, you can use the unprefixed fields
Directory: amd64/hello-world/nanoserver
# or use the prefixed versions
windows-amd64-GitCommit: 7d0ee592e4ed60e2da9d59331e16ecdcadc1ed87
Constraints: nanoserver
See the instruction format section for more information on the format of the library file.
Also see the Multiple Architectures