Get package dependencies of derived container image

get-dependencies.sh

#!/usr/bin/env bash

# Outputs the set of packages that are dependencies of the packages added by a derived container image.

baseTag="debian:buster-slim"
derivedTag="mcr.microsoft.com/dotnet/aspnet:3.1"

containerCmd="apt list --installed 2>/dev/null | grep installed | sed -n 's/^\([^/]*\).*/\1/p' | sort"

deltaPkgs=$(comm -13 <(docker run --rm $baseTag /bin/sh -c "$containerCmd") <(docker run --rm $derivedTag /bin/sh -c "$containerCmd") | tr '\n' ' ')

docker run --rm $derivedTag \
    /bin/sh -c "\
        apt update 1>/dev/null 2>/dev/null && \
        apt install -y apt-rdepends 1>/dev/null 2>/dev/null && \
        apt-rdepends 2>/dev/null $deltaPkgs | grep '^\S.*' | sort"