Provided a way to set the user ID

Dockerfile

@@ -19,10 +19,12 @@ RUN curl -LSo murmur.tar.bz2 ${BZIP_URL} \
 FROM alpine:3.11
 LABEL maintainer="Drew Short <warrick@sothr.com>"
 
+ARG USER_ID=9000
+
 WORKDIR /opt/mumble
 
 RUN mkdir -pv /opt/mumble /etc/mumble
-RUN adduser -DHs /sbin/nologin mumble
+RUN adduser -DHs /sbin/nologin -u ${USER_ID} mumble
 
 COPY --from=downloader /opt/mumble /opt/mumble
 COPY files/config.ini /etc/mumble/config.ini

Makefile

@@ -2,7 +2,6 @@ IMAGE_NAME="sothr/mumble"
 IMAGE_TAG="$$(grep 'ARG MUMBLE_VERSION' Dockerfile | awk -F = '{print $$2}')"
 
 build:
-	@echo "${IMAGE_TAG}" > tag
 	@docker build --force-rm --pull --tag $(IMAGE_NAME):$(IMAGE_TAG) .
 
 purge: