49 lines
1.6 KiB
Bash
49 lines
1.6 KiB
Bash
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set -e
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verbose=1
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image="$1"
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export searchpath="$2"
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export tarfile="$(mktemp)-$image.tar"
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# Save image tar to temp file
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[ $verbose ] && >&2 echo "Exporting image '$image' to temp file '$tarfile'..."
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docker image save "$image" -o "$tarfile"
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# Set up cleanup to not leave image behind
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function onexit() {
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[ $verbose ] && >&2 echo "Cleaning up exported image '$tarfile'"
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rm "$tarfile"
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}
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trap onexit EXIT
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# Extract manifest and config file contents
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[ $verbose ] && >&2 echo "Collecting metadata from image..."
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manifest=$(tar -xf "$tarfile" -x manifest.json -O | jq)
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config_file=$(echo "$manifest" | jq -r '.[0].Config')
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config=$(tar -f "$tarfile" -x "$config_file" -O | jq)
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# Combine manifest.json and config json to build a map from tar layer directory to layer id sha
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export idmap=$(echo "$manifest" "$config" | jq -sr '[ [ .[0][0].Layers, .[1].rootfs.diff_ids ] | transpose[] | { (.[0]): .[1] } ] | reduce .[] as $x ({}; . * $x)')
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# Search each layer for a file matching $searchpath
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# TODO also search for related whiteout files that start with `.wh.`
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[ $verbose ] && >&2 echo "Searching layers for '$searchpath'..."
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found=$(echo "$manifest" | jq '.[0].Layers[]' | xargs -I {} sh -c 'digest=$(echo "$idmap" | jq -r ".[\"{}\"]"); tar -f "$tarfile" -x {} -O | tar -t | sed s_^_/_ | grep -wx "$searchpath" | xargs -I [] echo "[]=$digest"')
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# If more than one is found, then bail
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if [ $(echo "$found" | wc -l) -gt 1 ]; then
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>&2 echo "Multiple matches found, aborting:"
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>&2 echo "$found"
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exit 2
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fi
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# print out labels to add during image rebuild
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labels=$(echo "$found" | sed 's_^.*$_--label "\0"_' | paste -d' ')
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echo "$labels"
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[ $verbose ] && >&2 echo "Done!"
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exit
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