An example of how to build the `concourse/concourse` image with a modified `gdn`

Dockerfile

FROM golang AS base

	RUN apt update && \
		apt install -y \
			git gcc libseccomp-dev
	
	ENV \
		CC=gcc \
		CGO_ENABLED=1


FROM base AS gdn-base

	COPY ./src /src
	WORKDIR /src/guardian


FROM gdn-base AS gdn-build

	RUN go build \
		-tags netgo \
		-ldflags "-extldflags '-static'" \
		-o /bin/gdn \
		./cmd/gdn

FROM gdn-base AS gdn-dadoo-build

	RUN go build \
		-tags netgo \
		-ldflags "-extldflags '-static'" \
		-o /bin/dadoo \
		./cmd/dadoo

FROM gdn-base AS gdn-init-build

	RUN set -x && \
		cd ./cmd/init && \
		$CC -static -o /bin/init \
		init.c ignore_sigchild.c


FROM concourse/concourse

	ARG RUNC_URL=https://github.com/opencontainers/runc/releases/download/v1.0.0-rc8/runc.amd64

	RUN apt update && apt install -y iptables curl
	RUN curl -SOL ${RUNC_URL} && install -m 0755 ./runc.amd64 /usr/local/concourse/bin/runc

	ENV CONCOURSE_GARDEN_BIN 	      /usr/local/concourse/bin/gdn
	ENV CONCOURSE_GARDEN_INIT_BIN 	      /usr/local/concourse/bin/init
	ENV CONCOURSE_GARDEN_RUNTIME_PLUGIN   /usr/local/concourse/bin/runc
	ENV CONCOURSE_GARDEN_DADOO_BIN 	      /usr/local/concourse/bin/dadoo

	COPY --from=gdn-dadoo-build /bin/dadoo /usr/local/concourse/bin/dadoo
	COPY --from=gdn-init-build  /bin/init  /usr/local/concourse/bin/init
	COPY --from=gdn-build       /bin/gdn   /usr/local/concourse/bin/gdn

Usage:

1. clone garden-runc-release, the "umbrella repo" from guardian

$ git clone https://github.com/cloudfoundry/garden-runc-release --recurse-submodules -j4

2. modify guardian (under ./src/guardian)

3. build the modified concourse image

$ docker build -t cirocosta/modified-concourse .