use nginx:alpine as base.

nginx/Dockerfile

@@ -1,15 +1,14 @@
-FROM nginx:latest
+FROM nginx:alpine
 
 MAINTAINER Mahmoud Zalt <mahmoud@zalt.me>
 
 ADD nginx.conf /etc/nginx/
-ADD laravel.conf /etc/nginx/sites-available/
+ADD laravel.conf /etc/nginx/conf.d/laravel.conf
 
 ARG PHP_UPSTREAM
 
-RUN echo "upstream php-upstream { server ${PHP_UPSTREAM}:9000; }" > /etc/nginx/conf.d/upstream.conf
-
-RUN usermod -u 1000 www-data
+RUN rm /etc/nginx/conf.d/default.conf \
+    && echo "upstream php-upstream { server ${PHP_UPSTREAM}:9000; }" > /etc/nginx/conf.d/upstream.conf
 
 CMD ["nginx"]