Use an alpine base image

Dockerfile

@@ -1,33 +1,50 @@
-FROM ubuntu:19.10
+FROM golang:1.14.2-alpine3.11 as gobuilder
 
-RUN apt update && apt install -y ruby ruby-dev build-essential wget
+ARG GOOS=linux
+ARG GOARCH=amd64
+ARG CGO_ENABLED=0
 
-COPY Gemfile .
-RUN gem install bundler
-RUN bundle install
+RUN apk add --no-cache --update \
+      bash \
+      binutils \
+      build-base \
+      ca-certificates \
+      curl
 
 ENV TERRAGRUNT_VERSION=0.23.8
-
-RUN wget https://github.com/gruntwork-io/terragrunt/releases/download/v${TERRAGRUNT_VERSION}/terragrunt_linux_amd64 && \
-    mv terragrunt_linux_amd64 /usr/bin/terragrunt && \
-    chmod 755 /usr/bin/terragrunt
+RUN curl -fsSL -o /usr/local/bin/terragrunt \
+      https://github.com/gruntwork-io/terragrunt/releases/download/v${TERRAGRUNT_VERSION}/terragrunt_linux_amd64
 
 ENV TERRAFORM_VERSION=0.12.24
-
-RUN wget https://releases.hashicorp.com/terraform/${TERRAFORM_VERSION}/terraform_${TERRAFORM_VERSION}_linux_amd64.zip && \
+RUN curl -fsSL -O https://releases.hashicorp.com/terraform/${TERRAFORM_VERSION}/terraform_${TERRAFORM_VERSION}_linux_amd64.zip && \
     unzip terraform_${TERRAFORM_VERSION}_linux_amd64.zip && \
-    mv terraform /usr/bin/ && \
-    chmod 755 /usr/bin/terraform && \
-    rm terraform_${TERRAFORM_VERSION}_linux_amd64.zip
-
-ENV OPA_VERSION=0.18.0
+    mv terraform /usr/local/bin/
 
-RUN wget https://github.com/open-policy-agent/opa/releases/download/v${OPA_VERSION}/opa_linux_amd64 && \
-    mv opa_linux_amd64 /usr/bin/opa && \
-    chmod 755 /usr/bin/opa
+ENV OPA_VERSION=0.19.1
+WORKDIR /opa-build
+RUN curl -fsSL "https://codeload.github.com/open-policy-agent/opa/tar.gz/v${OPA_VERSION}" | tar xvz --strip-components=1 && \
+    go build && \
+    mv opa /usr/local/bin/
 
 ENV CONFTEST_VERSION=0.18.1
+RUN curl -fsSL https://github.com/instrumenta/conftest/releases/download/v${CONFTEST_VERSION}/conftest_${CONFTEST_VERSION}_Linux_x86_64.tar.gz | \
+      tar xz conftest -C /usr/local/bin/
+
+RUN strip --strip-all /usr/local/bin/* && \
+    chmod 0755 /usr/local/bin/*
+
+FROM alpine:3.11.5
+LABEL maintainer="Rémi REY <[email protected]>"
+
+COPY --from=gobuilder /usr/local/bin/ /usr/bin/
+COPY Gemfile .
 
-RUN wget https://github.com/instrumenta/conftest/releases/download/v${CONFTEST_VERSION}/conftest_${CONFTEST_VERSION}_linux_amd64.deb && \
-    dpkg -i conftest_${CONFTEST_VERSION}_linux_amd64.deb && \
-    rm conftest_${CONFTEST_VERSION}_linux_amd64.deb
+RUN apk add --no-cache --update \
+      ruby && \
+    apk add --no-cache --update --virtual build-dependencies \
+      build-base \
+      ruby-dev && \
+    gem install bundler && \
+    bundle config set no-cache true && \
+    bundle install --jobs $(getconf _NPROCESSORS_ONLN) && \
+    apk del build-dependencies