Replaced ubuntu:latest with ubuntu:18.04; specific image version to make grafana build images consistent (#18224)

Dockerfile

@@ -33,7 +33,7 @@ ENV NODE_ENV production
 RUN ./node_modules/.bin/grunt build
 
 # Final container
-FROM ubuntu:latest
+FROM ubuntu:18.04
 
 LABEL maintainer="Grafana team <hello@grafana.com>"
 

packaging/docker/Dockerfile

@@ -1,4 +1,4 @@
-ARG BASE_IMAGE=ubuntu:latest
+ARG BASE_IMAGE=ubuntu:18.04
 FROM ${BASE_IMAGE}
 
 ARG GRAFANA_TGZ="grafana-latest.linux-x64.tar.gz"
@@ -12,7 +12,7 @@ COPY ${GRAFANA_TGZ} /tmp/grafana.tar.gz
 # Change to tar xfzv to make tar print every file it extracts
 RUN mkdir /tmp/grafana && tar xfz /tmp/grafana.tar.gz --strip-components=1 -C /tmp/grafana
 
-ARG BASE_IMAGE=ubuntu:latest
+ARG BASE_IMAGE=ubuntu:18.04
 FROM ${BASE_IMAGE}
 
 ARG GF_UID="472"

packaging/docker/build.sh

@@ -59,10 +59,10 @@ docker_tag_all () {
 	fi
 }
 
-docker_build "ubuntu:latest" "grafana-latest.linux-x64.tar.gz" "${_docker_repo}:${_grafana_version}"
+docker_build "ubuntu:18.04" "grafana-latest.linux-x64.tar.gz" "${_docker_repo}:${_grafana_version}"
 if [ $BUILD_FAST = "0" ]; then
-	docker_build "arm32v7/ubuntu:latest" "grafana-latest.linux-armv7.tar.gz" "${_docker_repo}-arm32v7-linux:${_grafana_version}"
-	docker_build "arm64v8/ubuntu:latest" "grafana-latest.linux-arm64.tar.gz" "${_docker_repo}-arm64v8-linux:${_grafana_version}"
+	docker_build "arm32v7/ubuntu:18.04" "grafana-latest.linux-armv7.tar.gz" "${_docker_repo}-arm32v7-linux:${_grafana_version}"
+	docker_build "arm64v8/ubuntu:18.04" "grafana-latest.linux-arm64.tar.gz" "${_docker_repo}-arm64v8-linux:${_grafana_version}"
 fi
 # Tag as 'latest' for official release; otherwise tag as grafana/grafana:master
 if echo "$_grafana_tag" | grep -q "^v"; then