4911a10a4e
XZ compresses significantly better than bzip2. Here are the compression ratios and execution times (using 4 cores in parallel) on my /var/run/current-system (3.1 GiB): bzip2: total compressed size 849.56 MiB, 30.8% [2m08] xz -6: total compressed size 641.84 MiB, 23.4% [6m53] xz -7: total compressed size 621.82 MiB, 22.6% [7m19] xz -8: total compressed size 599.33 MiB, 21.8% [7m18] xz -9: total compressed size 588.18 MiB, 21.4% [7m40] Note that compression takes much longer. More importantly, however, decompression is much faster: bzip2: 1m47.274s xz -6: 0m55.446s xz -7: 0m54.119s xz -8: 0m52.388s xz -9: 0m51.842s The only downside to using -9 is that decompression takes a fair amount (~65 MB) of memory.
36 lines
704 B
Nix
36 lines
704 B
Nix
with import <nix/config.nix>;
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let
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builder = builtins.toFile "nar.sh"
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''
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export PATH=${nixBinDir}:${coreutils}
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echo "packing ‘$storePath’..."
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mkdir $out
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dst=$out/tmp.nar.xz
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set -o pipefail
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nix-store --dump "$storePath" | ${xz} -9 > $dst
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hash=$(nix-hash --flat --type $hashAlgo --base32 $dst)
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echo -n $hash > $out/nar-compressed-hash
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mv $dst $out/$hash.nar.xz
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'';
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in
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{ storePath, hashAlgo }:
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derivation {
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name = "nar";
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system = builtins.currentSystem;
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builder = shell;
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args = [ "-e" builder ];
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inherit storePath hashAlgo;
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# Don't build in a chroot because Nix's dependencies may not be there.
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__noChroot = true;
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}
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