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0aeba64fb2
the nix store may contain hardlinks: derivations may output them directly, or users may be using store optimization which automatically hardlinks identical files in the nix store. The presence of these links are intended to be a 'transparent' optimization. However, when creating a squashfs image, the image will be different depending on whether hard links were present on the filesystem, leading to reproducibility problems. By passing '-no-hardlinks' to mksquashfs the files are stored as duplicates in the squashfs image. Since squashfs has support for duplicate files this does not lead to a larger image. For more details see https://github.com/NixOS/nixpkgs/issues/114331
29 lines
847 B
Nix
29 lines
847 B
Nix
{ stdenv, squashfsTools, closureInfo
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, # The root directory of the squashfs filesystem is filled with the
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# closures of the Nix store paths listed here.
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storeContents ? []
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, # Compression parameters.
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# For zstd compression you can use "zstd -Xcompression-level 6".
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comp ? "xz -Xdict-size 100%"
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}:
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stdenv.mkDerivation {
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name = "squashfs.img";
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nativeBuildInputs = [ squashfsTools ];
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buildCommand =
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''
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closureInfo=${closureInfo { rootPaths = storeContents; }}
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# Also include a manifest of the closures in a format suitable
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# for nix-store --load-db.
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cp $closureInfo/registration nix-path-registration
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# Generate the squashfs image.
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mksquashfs nix-path-registration $(cat $closureInfo/store-paths) $out \
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-no-hardlinks -keep-as-directory -all-root -b 1048576 -comp ${comp}
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'';
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}
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