cleanup Dockerfile: put ARGs before FROM, setup ENTRYPOINT at end

Author: ehough

Dockerfile

@@ -1,24 +1,19 @@
-# switch back to Alpine when/if https://bugs.alpinelinux.org/issues/8470 is fixed
-# FROM alpine:latest
-# RUN apk --update upgrade && apk add bash nfs-utils && rm -rf /var/cache/apk/*
-
+# Alpine can only be used if/when this bug is fixed: https://bugs.alpinelinux.org/issues/8470
 ARG BUILD_FROM=debian:stretch-slim
 
-FROM $BUILD_FROM
-
 # https://github.com/ehough/docker-nfs-server/pull/3#issuecomment-387880692
 ARG DEBIAN_FRONTEND=noninteractive
 
-# kmod is required for lsmod
-# libcap2-bin is required for checking capabilities
+FROM $BUILD_FROM
+
+# kmod is needed for lsmod, and libcap2-bin is needed for confirming Linux capabilities
 RUN apt-get update                                                                && \
     apt-get install -y --no-install-recommends nfs-kernel-server kmod libcap2-bin && \
     apt-get clean                                                                 && \
     rm -rf /var/lib/apt/lists                                                     && \
-    rm /etc/idmapd.conf # remove the default idmapd.conf
-
-ADD ./entrypoint.sh /usr/local/bin
-RUN chmod +x /usr/local/bin/entrypoint.sh
+                                                                                     \
+    # remove the default idmapd.conf
+    rm -v /etc/idmapd.conf
 
 # http://wiki.linux-nfs.org/wiki/index.php/Nfsv4_configuration
 RUN mkdir -p /var/lib/nfs/rpc_pipefs && \
@@ -28,4 +23,6 @@ RUN mkdir -p /var/lib/nfs/rpc_pipefs && \
 
 EXPOSE 2049
 
+# setup entrypoint
+COPY ./entrypoint.sh /usr/local/bin
 ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]