#!/usr/bin/env bash

# This script takes a single Docker image tag (e.g. "ubuntu:latest") as input

# and shows the contents of the filesystem for each layer in the image.

if [ $# -ne 1 ]; then

echo "Usage: $0 <image_tag>"

exit 1

fi

IMAGE=$1

# TMPDIR=$(mktemp -d)

mkdir -p "$PWD/tmp"

TMPDIR="$PWD/tmp"

# Save the Docker image to a tar archive

echo "Saving Docker image '$IMAGE'..."

if ! docker save "$IMAGE" | pv > "${TMPDIR}/image.tar"; then

echo "Failed to save image '$IMAGE'. Make sure the image exists and Docker is running."

rm -rf "${TMPDIR}"

exit 1

fi

cd "${TMPDIR}" || exit 1

# Extract the top-level metadata of the image tar

echo "Extracting image metadata..."

pwd

tar -xzf image.tar

chmod -R 777 .

cd blobs/sha256 || exit 1

# Typically, the saved image will contain multiple directories each representing a layer.

# Each layer directory should have a 'layer.tar' file that contains the filesystem for that layer.

for LAYERFILE in ./*; do

if [ -f "${LAYERFILE}" ]; then

mv "${LAYERFILE}" "${LAYERFILE}.tar"

mkdir -p "${LAYERFILE}"

tar -xzf "${LAYERFILE}.tar" -C "${LAYERFILE}"

rm "${LAYERFILE}.tar"

echo "-----------------------------------------------------------------"

echo "Contents of layer: ${LAYERFILE%/}"

echo "-----------------------------------------------------------------"

# List the files in the layer.tar without extracting

tree -L 2 "${LAYERFILE}"

echo

fi

done