Quick and dirty "docker pull"-like shell script.

docker-pull.sh

#!/usr/bin/env bash

set -eu

name="library/redis"
tag="latest"

registry="https://registry-1.docker.io"
blobs="blobs"
data="images/$name/$tag"
image="$data/image"
manifest="$data/manifest.json"

rm -rf "$image"
mkdir -p "$blobs" "$data" "$image"

# get the manifest.json
curl -L "$registry/v2/manifest/$name/$tag" -o "$manifest"

# for each layer in the manifest
jq -r '.fsLayers[] | .blobSum' < "$manifest" | tail -r | sed 's/:/\//' | while read blobsum; do
  blobsumpath="$blobs/$(basename "$blobsum")"
  # download the layer. -z checks to see if the file has been downloaded
  curl -L "$registry/v2/blob/$name/$blobsum" -z "$blobsumpath" -o "$blobsumpath"
  # extract the layer
  tar -x -f "$blobsumpath" -C "$image"
  # delete .wh.* and their corresponding files
  find "$image" -name '.wh.*' -print -exec sh -c 'rm -rf "{}" "$(echo "{}" | sed s/.wh.//)"' \; 2> /dev/null || true
done