50 lines
1.6 KiB
Bash
Executable file
50 lines
1.6 KiB
Bash
Executable file
#!@shell@
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set -eu
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layerNumber=$1
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shift
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layerPath="./layers/$layerNumber"
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echo "Creating layer #$layerNumber for $@"
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mkdir -p "$layerPath"
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# Make sure /nix and /nix/store appear first in the archive.
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#
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# We create the directories here and use them because
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# when there are other things being added to the
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# nix store, tar could fail, saying,
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# "tar: /nix/store: file changed as we read it"
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mkdir -p nix/store
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# Then we change into the /nix/store in order to
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# avoid a similar "file changed as we read it" error
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# as above. Namely, if we use the absolute path of
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# /nix/store/123-pkg and something new is added to the nix
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# store while tar is running, it will detect a change to
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# /nix/store and fail. Instead, if we cd into the nix store
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# and copy the relative nix store path, tar will ignore
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# changes to /nix/store. In order to create the correct
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# structure in the tar file, we transform the relative nix
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# store path to the absolute store path.
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tarhash=$(
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basename -a "$@" |
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tar --create --preserve-permissions --absolute-names nix \
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--directory /nix/store --verbatim-files-from --files-from - \
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--hard-dereference --sort=name \
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--mtime="@$SOURCE_DATE_EPOCH" \
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--owner=0 --group=0 \
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--transform 's,^nix$,/\0,' \
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--transform 's,^nix/store$,/\0,' \
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--transform 's,^[^/],/nix/store/\0,rS' |
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tee "$layerPath/layer.tar" |
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tarsum
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)
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# Add a 'checksum' field to the JSON, with the value set to the
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# checksum of the tarball.
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cat ./generic.json | jshon -s "$tarhash" -i checksum > $layerPath/json
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# Indicate to docker that we're using schema version 1.0.
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echo -n "1.0" > $layerPath/VERSION
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