Fix nginx error

Dockerfile

@@ -3,15 +3,17 @@ FROM alpine:latest
 
 MAINTAINER Golfen Guo <golfen.guo@daocloud.io> 
 
-# Install Nginx
+# Install and configure Nginx
 RUN apk --update add nginx
-
+RUN sed -i "s#root   html;#root   /usr/share/nginx/html;#g" /etc/nginx/nginx.conf
+RUN ln -sf /dev/stdout /var/log/nginx/access.log \
+	&& ln -sf /dev/stderr /var/log/nginx/error.log
+
 # Add 2048 stuff into Nginx server
 COPY . /usr/share/nginx/html
 
 EXPOSE 80
-RUN ln -sf /dev/stdout /var/log/nginx/access.log \
-	&& ln -sf /dev/stderr /var/log/nginx/error.log
 
 # Start Nginx and keep it from running background
-CMD ["nginx", "-g", "daemon off;"]
+CMD ["nginx", "-g", "pid /tmp/nginx.pid; daemon off;"]
+