nixpkgs-suyu/pkgs/build-support/docker/pull.nix

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{ stdenv, lib, curl, jshon, python, runCommand }:
# Inspired and simplified version of fetchurl.
# For simplicity we only support sha256.
# Currently only registry v1 is supported, compatible with Docker Hub.
{ imageName, imageTag ? "latest", imageId ? null
, sha256, name ? "${imageName}-${imageTag}"
, indexUrl ? "https://index.docker.io"
, registryVersion ? "v1"
, curlOpts ? "" }:
assert registryVersion == "v1";
let layer = stdenv.mkDerivation {
inherit name imageName imageTag imageId
indexUrl registryVersion curlOpts;
builder = ./pull.sh;
detjson = ./detjson.py;
buildInputs = [ curl jshon python ];
outputHashAlgo = "sha256";
outputHash = sha256;
outputHashMode = "recursive";
impureEnvVars = lib.fetchers.proxyImpureEnvVars ++ [
# This variable allows the user to pass additional options to curl
"NIX_CURL_FLAGS"
];
# Doing the download on a remote machine just duplicates network
# traffic, so don't do that.
preferLocalBuild = true;
};
in runCommand "${name}.tar.gz" {} ''
tar -C ${layer} -czf $out .
''