35 lines
1.5 KiB
Docker
35 lines
1.5 KiB
Docker
# syntax=docker/dockerfile:1
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# The cross-built images have the build arch (`amd64`) embedded in the image
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# manifest, rather than the target arch. For example:
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#
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# $ docker inspect vaultwarden/server:latest-armv7 | jq -r '.[]|.Architecture'
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# amd64
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#
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# Recent versions of Docker have started printing a warning when the image's
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# claimed arch doesn't match the host arch. For example:
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#
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# WARNING: The requested image's platform (linux/amd64) does not match the
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# detected host platform (linux/arm/v7) and no specific platform was requested
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#
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# The image still works fine, but the spurious warning creates confusion.
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#
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# Docker doesn't seem to provide a way to directly set the arch of an image
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# at build time. To resolve the build vs. target arch discrepancy, we use
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# Docker Buildx to build a new set of images with the correct target arch.
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#
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# Docker Buildx uses this Dockerfile to build an image for each requested
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# platform. Since the Dockerfile basically consists of a single `FROM`
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# instruction, we're effectively telling Buildx to build a platform-specific
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# image by simply copying the existing cross-built image and setting the
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# correct target arch as a side effect.
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#
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# References:
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#
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# - https://docs.docker.com/buildx/working-with-buildx/#build-multi-platform-images
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# - https://docs.docker.com/engine/reference/builder/#automatic-platform-args-in-the-global-scope
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# - https://docs.docker.com/engine/reference/builder/#understand-how-arg-and-from-interact
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#
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ARG LOCAL_REPO
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ARG DOCKER_TAG
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FROM ${LOCAL_REPO}:${DOCKER_TAG}-${TARGETARCH}${TARGETVARIANT}
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