Dockerfile

# Stage: s6-overlay-base
# Purpose: Installs s6-overlay and rootfs
# Comments:
#  - Don't leave anything extra in here either
FROM docker.io/alpine:3.21 AS s6-overlay-base

WORKDIR /usr/src/s6

# https://github.com/just-containers/s6-overlay#customizing-s6-overlay-behaviour
ENV \
    LANG="C.UTF-8" \
    S6_BEHAVIOUR_IF_STAGE2_FAILS=2 \
    S6_CMD_WAIT_FOR_SERVICES_MAXTIME=0 \
    S6_CMD_WAIT_FOR_SERVICES=1 \
    S6_VERBOSITY=1

# Buildx provided, must be defined to use though
ARG TARGETARCH
ARG TARGETVARIANT
# Lock this version
ARG S6_OVERLAY_VERSION=3.2.0.2

RUN set -eux \
    && echo "Installing build time packages" \
      && apk add --no-cache --virtual temp-pkgs \
        curl \
        xz \
    && echo "Determining arch" \
      && S6_ARCH="" \
      && if [ "${TARGETARCH}${TARGETVARIANT}" = "amd64" ]; then S6_ARCH="x86_64"; \
      elif [ "${TARGETARCH}${TARGETVARIANT}" = "arm64" ]; then S6_ARCH="aarch64"; \
      elif [ "${TARGETARCH}${TARGETVARIANT}" = "armv7" ]; then S6_ARCH="armhf"; fi \
      && if [ -z "${S6_ARCH}" ]; then { echo "Error: Not able to determine arch"; exit 1; }; fi \
    && echo "Installing s6-overlay for ${S6_ARCH}" \
      && curl --fail --silent --show-error --location --output s6-overlay-noarch.tar.xz \
        "https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-noarch.tar.xz" \
      && curl --fail --silent --show-error --location --output s6-overlay-noarch.tar.xz.sha256 \
        "https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-noarch.tar.xz.sha256" \
      && curl --fail --silent --show-error --location --output s6-overlay-${S6_ARCH}.tar.xz \
        "https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-${S6_ARCH}.tar.xz" \
      && curl --fail --silent --show-error --location --output s6-overlay-${S6_ARCH}.tar.xz.sha256 \
        "https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-${S6_ARCH}.tar.xz.sha256" \
      && echo "Validating s6-archive checksums" \
        && sha256sum -c ./*.sha256 \
      && echo "Unpacking archives" \
        && tar -C / -Jxpf s6-overlay-noarch.tar.xz \
        && tar -C / -Jxpf s6-overlay-${S6_ARCH}.tar.xz \
      && echo "Removing downloaded archives" \
        && rm ./*.tar.xz \
        && rm ./*.sha256 \
    && echo "Cleaning up image" \
      && apk --no-cache del temp-pkgs

# Copy our s6 definitions and configuration
COPY ./rootfs /

# Stage: main-app
# Purpose: The final image
# Comments:
#  - Don't leave anything extra in here
FROM s6-overlay-base AS main-app

RUN set -eux \
    && echo "Installing dnsmasq" \
        && apk add --no-cache dnsmasq

WORKDIR /opt/

ENTRYPOINT [ "/init" ]