jordansissel

% docker build -t rust . 
...

# Export the image to tarball, which itself contains tarballs and a manifest.json
% docker save -o rust.tar rust 

# Extract the last layer
# tar's -O flag extracts a single entry from the tarball.
# The file we want is the last "Layer" in the manifest.json
% tar -xf rust.tar -O $(tar -xf rust.tar -O manifest.json | jq -r '.[].Layers[-1]') > curlbash.tar