From 9c2efb6c9f87df108537d3efadc97cf3803359ed Mon Sep 17 00:00:00 2001
From: Dominik Menke <git@dmke.org>
Date: Mon, 11 Apr 2022 17:09:40 +0200
Subject: [PATCH] Reduce Docker image size (#24)

By using Alpine instead of Ubuntu, the resulting image is around
110 MB smaller:

    $ docker images
    REPOSITORY       TAG      CREATED         SIZE
    unms-exporter    alpine   3 seconds ago   20MB
    unms-exporter    ubuntu   5 minutes ago   132MB

We could save 5 MB more by using `FROM scratch` instead of Alpine,
but then handling of timezone and CA certificate files becomes a
hassle.
---
 Dockerfile | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index 015ee14..7497367 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,15 +1,17 @@
-FROM golang:1.18 AS build
+FROM golang:1.18-alpine AS build
 
 WORKDIR /src
 COPY go.mod go.sum ./
 RUN go mod download
 
+ENV CGO_ENABLED=0
+
 COPY . ./
-RUN go build -o unms-exporter main.go
+RUN go build -ldflags="-s -w" -trimpath -o unms-exporter main.go
 
-FROM ubuntu:20.04
+FROM alpine
 
-RUN apt-get -q update && apt-get -yq install ca-certificates
+RUN apk add --no-cache tzdata ca-certificates
 COPY --from=build /src/unms-exporter /usr/local/bin/
 
 CMD ["/usr/local/bin/unms-exporter"]