A simple script to demonstrate how to fetch and unpack a container image from a registry. Used here with the latest version of the Postgres image

fetch_unpack_latest_postgres_container_image_dockerhub.sh

#!/bin/sh

TOKEN=$( curl -s "https://auth.docker.io/token?service=registry.docker.io&scope=repository:library/postgres:pull" \
    	| jq -r .token )

MANIFEST_INDEX=$( curl -s -H "Authorization: Bearer $TOKEN" \
    	https://registry-1.docker.io/v2/library/postgres/manifests/latest )

AMD64_MANIFEST_DIGEST=$( echo $MANIFEST_INDEX \
    	|jq -r '.manifests[] | select(.platform.architecture == "amd64") .digest' )

AMD64_MANIFEST=$( curl -s -H "Authorization: Bearer $TOKEN" \
    	-H "Accept: application/vnd.oci.image.manifest.v1+json" \
    	https://registry-1.docker.io/v2/library/postgres/manifests/$AMD64_MANIFEST_DIGEST )

LAYERS=$( echo $AMD64_MANIFEST \
    	|jq -r '.layers[] | select(.mediaType == "application/vnd.oci.image.layer.v1.tar+gzip") .digest' )

tempfile=/tmp/$(date +%N)
mkdir $tempfile
cd $tempfile

for layer in $LAYERS
do
    	curl -s -H "Authorization: Bearer $TOKEN" --location \
    	https://registry-1.docker.io/v2/library/postgres/blobs/$layer \
    	| tar xzf -
done

echo "Image unpackaged at $tempfile"