Dockerfile: mount DEB sources instead of copy to reduce image size#914
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stklcode wants to merge 1 commit into
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Dockerfile: mount DEB sources instead of copy to reduce image size#914stklcode wants to merge 1 commit into
stklcode wants to merge 1 commit into
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The DEB package is used temporarily and deleted after installation. The intermediate layer still exists which bloats the final image by about 300MB without any real benefit. Mount (bind) the context directory to /source and drop the COPY layers to reduce the image size. This feature requires BuildKit or an equivalent platform that supports mounts. It is available since Docker v18.09 and default since v23.0 and should not be an issue in modern build environments.
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General information
This PR affects the Dockerfile and targets size reduction of the published images.
Proposed changes
The DEB package is used temporarily and deleted after installation. The intermediate layer still exists which bloats the final image by about 300MB without any real benefit. The DEB file is deleted anyway, so the COPY layer is effectively hidden.
Mount (bind) the context directory to /source and drop the COPY layers to reduce the image size.
This feature requires BuildKit or an equivalent platform that supports mounts. It is available since Docker v18.09 and default since v23.0 and should not be an issue in modern build environments.
(with older Docker 18-22
DOCKER_BUILDKIT=1is required)Reference: https://docs.docker.com/reference/dockerfile/#run---mounttypebind
Additional notes
We mount the entire context using
RUN --mount,type=bind,target=/sourcefor the CMK installation. This could be narrowed down to mount only the required files (like we do for needed-packages), but the only difference here is cachng behavior.Using other builders like rootless Podman with SELinux enabled, monting requires proper container_file_t labels or relabelling (e.g.
--mount=type=bind,target=/source,relabel=private). Using Docker/BuildKit or Buildah in most CI environments should be fine without.Test build (using Podman 5.8 on Linux). Upstream image for reference and two custom builds with/without optimization for comparison.
Size comparison
Layer history