Use multi-stage build to reduce image size

Signed-off-by: Knut Ahlers <knut@ahlers.me>

Dockerfile

@@ -1,22 +1,35 @@
-FROM golang:alpine
-
-LABEL maintainer "Knut Ahlers <knut@ahlers.me>"
+FROM golang:alpine as builder
 
 ADD . /go/src/github.com/Luzifer/nginx-sso
 WORKDIR /go/src/github.com/Luzifer/nginx-sso
 
 RUN set -ex \
- && apk --no-cache add git ca-certificates bash curl \
- && go install -ldflags "-X main.version=$(git describe --tags || git rev-parse --short HEAD || echo dev)" \
+ && apk add --update git \
+ && go install -ldflags "-X main.version=$(git describe --tags || git rev-parse --short HEAD || echo dev)"
+
+FROM alpine:3.8
+
+LABEL maintainer "Knut Ahlers <knut@ahlers.me>"
+
+RUN set -ex \
+ && apk --no-cache add \
+      bash \
+      ca-certificates \
+      curl \
  && curl -sSfLo /usr/local/bin/dumb-init https://github.com/Yelp/dumb-init/releases/download/v1.2.1/dumb-init_1.2.1_amd64 \
  && chmod +x /usr/local/bin/dumb-init \
- && apk --no-cache del --purge git curl
+ && apk --no-cache del --purge \
+      curl
 
-EXPOSE 8082
+COPY --from=builder /go/bin/nginx-sso                                     /usr/local/bin/
+COPY --from=builder /go/src/github.com/Luzifer/nginx-sso/config.yaml      /usr/local/share/nginx-sso/
+COPY --from=builder /go/src/github.com/Luzifer/nginx-sso/docker-start.sh  /usr/local/bin/
+COPY --from=builder /go/src/github.com/Luzifer/nginx-sso/frontend/*       /usr/local/share/nginx-sso/frontend/
 
+EXPOSE 8082
 VOLUME ["/data"]
 
-ADD docker-start.sh /usr/local/bin
-
 ENTRYPOINT ["/usr/local/bin/docker-start.sh"]
 CMD ["--"]
+
+# vim: set ft=Dockerfile:

docker-start.sh

@@ -2,16 +2,16 @@
 set -euo pipefail
 
 # Copy frontend if not available
-[ -d /data/frontend ] || cp -r /go/src/github.com/Luzifer/nginx-sso/frontend /data/frontend
+[ -d /data/frontend ] || cp -r /usr/local/share/nginx-sso/frontend /data/frontend
 
 [ -e /data/config.yaml ] || {
-  cp /go/src/github.com/Luzifer/nginx-sso/config.yaml /data/config.yaml
-  echo "An example configuration was copied to /data/config.yaml - You want to edit that one!"
-  exit 1
+	cp /usr/local/share/nginx-sso/config.yaml /data/config.yaml
+	echo "An example configuration was copied to /data/config.yaml - You want to edit that one!"
+	exit 1
 }
 
 echo "Starting nginx-sso"
-exec /go/bin/nginx-sso \
-  --config /data/config.yaml \
-  --frontend-dir /data/frontend \
-  $@
+exec /usr/local/bin/nginx-sso \
+	--config /data/config.yaml \
+	--frontend-dir /data/frontend \
+	$@