Improve Docker image build reproducibility #36906
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This is to improve image creation reproducibility. Since the nar format doesn't support hard link, the tar stream of a layer can be different if a dependency of a layer has been built locally or if it has been fetched from a binary cache. If the dependency has been build locally, it can contain hard links which are encoded in the tar stream. If the dependency has been fetched from a binary cache, the tar stream doesn't contain any hard link. So even if the content is the same, tar streams are different.
This is to go to a reproducible image build. Note without this options image are identical from the Docker point of view but generated docker archives could have different hashes.
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@GrahamcOfBorg test docker-tools |
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No attempt on x86_64-linux The following builds were skipped because they don't evaluate on x86_64-linux: tests.docker-tools No log is available. |
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Success on aarch64-linux (full log) Attempted: tests.docker-tools No log is available. |
globin
approved these changes
Mar 13, 2018
Profpatsch
approved these changes
Mar 13, 2018
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I backport it to 18.03. |
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Motivation for this change
Docker archives produced by our docker tools can differ even if the content is the same.
One of these patches dereferences hard links in the tar stream. I don't know how this can increase the size of produced images. On my images, I didn't observe a big difference.
@Profpatsch @kuznero
Things done
build-use-sandboxinnix.confon non-NixOS)nix-shell -p nox --run "nox-review wip"./result/bin/)