Build image from scratch based on alpine:3.7 to get PHP version 7.1

Dockerfile

-FROM docker:18.06.1
+FROM alpine:3.7
 
-LABEL com.example.vendor="PARAGON Executive Service GmbH" \
-      maintainer="juergen@paragon-es.de" \
-      version="1.1.0" \
+LABEL com.example.vendor="LakeDrops" \
+      maintainer="juergen.haas@lakedrops.com" \
+      version="1.2.0" \
       description="An image for GitLab runner to build and test Drupal projects."
 
 ARG compose_version=1.21.2
 ARG glibc_version=2.28-r0
 
+RUN apk add --no-cache \
+		ca-certificates
+
+# set up nsswitch.conf for Go's "netgo" implementation (which Docker explicitly uses)
+# - https://github.com/docker/docker-ce/blob/v17.09.0-ce/components/engine/hack/make.sh#L149
+# - https://github.com/golang/go/blob/go1.9.1/src/net/conf.go#L194-L275
+# - docker run --rm debian:stretch grep '^hosts:' /etc/nsswitch.conf
+RUN [ ! -e /etc/nsswitch.conf ] && echo 'hosts: files dns' > /etc/nsswitch.conf
+
+ENV DOCKER_CHANNEL stable
+ENV DOCKER_VERSION 18.06.1-ce
+# TODO ENV DOCKER_SHA256
+# https://github.com/docker/docker-ce/blob/5b073ee2cf564edee5adca05eee574142f7627bb/components/packaging/static/hash_files !!
+# (no SHA file artifacts on download.docker.com yet as of 2017-06-07 though)
+
+RUN set -eux; \
+	\
+# this "case" statement is generated via "update.sh"
+	apkArch="$(apk --print-arch)"; \
+	case "$apkArch" in \
+		x86_64) dockerArch='x86_64' ;; \
+		armhf) dockerArch='armel' ;; \
+		aarch64) dockerArch='aarch64' ;; \
+		ppc64le) dockerArch='ppc64le' ;; \
+		s390x) dockerArch='s390x' ;; \
+		*) echo >&2 "error: unsupported architecture ($apkArch)"; exit 1 ;;\
+	esac; \
+	\
+	if ! wget -O docker.tgz "https://download.docker.com/linux/static/${DOCKER_CHANNEL}/${dockerArch}/docker-${DOCKER_VERSION}.tgz"; then \
+		echo >&2 "error: failed to download 'docker-${DOCKER_VERSION}' from '${DOCKER_CHANNEL}' for '${dockerArch}'"; \
+		exit 1; \
+	fi; \
+	\
+	tar --extract \
+		--file docker.tgz \
+		--strip-components 1 \
+		--directory /usr/local/bin/ \
+	; \
+	rm docker.tgz; \
+	\
+	dockerd --version; \
+	docker --version
+
+COPY modprobe.sh /usr/local/bin/modprobe
+COPY docker-entrypoint.sh /usr/local/bin/
+
+ENTRYPOINT ["docker-entrypoint.sh"]
+CMD ["sh"]
+
 RUN mkdir -p /root/.ssh && \
     echo "StrictHostKeyChecking no" >> /root/.ssh/config && \
     \
     apk update && \
     apk add --no-cache curl openssl openssh ca-certificates wget make patch \
-        bash fish python nodejs npm git unzip \
+        bash fish python nodejs git unzip \
         php7 php7-phar php7-json php7-dom php7-gd php7-mbstring php7-openssl \
         php7-pdo php7-curl php7-xml php7-zip php7-session php7-ctype \
         php7-tokenizer php7-simplexml php7-xmlwriter && \

docker-entrypoint.sh

+#!/bin/sh
+set -e
+
+# first arg is `-f` or `--some-option`
+if [ "${1#-}" != "$1" ]; then
+	set -- docker "$@"
+fi
+
+# if our command is a valid Docker subcommand, let's invoke it through Docker instead
+# (this allows for "docker run docker ps", etc)
+if docker help "$1" > /dev/null 2>&1; then
+	set -- docker "$@"
+fi
+
+# if we have "--link some-docker:docker" and not DOCKER_HOST, let's set DOCKER_HOST automatically
+if [ -z "$DOCKER_HOST" -a "$DOCKER_PORT_2375_TCP" ]; then
+	export DOCKER_HOST='tcp://docker:2375'
+fi
+
+if [ "$1" = 'dockerd' ]; then
+	cat >&2 <<-'EOW'
+		📎 Hey there!  It looks like you're trying to run a Docker daemon.
+		   You probably should use the "dind" image variant instead, something like:
+		     docker run --privileged --name some-overlay-docker -d docker:stable-dind --storage-driver=overlay
+		   See https://hub.docker.com/_/docker/ for more documentation and usage examples.
+	EOW
+	sleep 3
+fi
+
+exec "$@"

modprobe.sh

+#!/bin/sh
+set -eu
+
+# "modprobe" without modprobe
+# https://twitter.com/lucabruno/status/902934379835662336
+
+# this isn't 100% fool-proof, but it'll have a much higher success rate than simply using the "real" modprobe
+
+# Docker often uses "modprobe -va foo bar baz"
+# so we ignore modules that start with "-"
+for module; do
+	if [ "${module#-}" = "$module" ]; then
+		ip link show "$module" || true
+		lsmod | grep "$module" || true
+	fi
+done
+
+# remove /usr/local/... from PATH so we can exec the real modprobe as a last resort
+export PATH='/usr/sbin:/usr/bin:/sbin:/bin'
+exec modprobe "$@"