Add the assignment to intgrate a build arg

[refs #c2f282de0b87]

Author: jfahrer

nginx/assignment5.md

@@ -0,0 +1,33 @@
+## Add a build argument to the nginx image
+* Define a build argument to define which package to install
+  * `nginx-light`
+  * `nginx-full`
+  * `nginx-extras`
+* Value should either be `light`, `full` or `extras`
+* Set the default to `full`
+* Make the installed package available in the environment variable `NGINX_PKG`
+  * For example `nginx-full`
+* Try building and testing the image
+* Add a Docker Compose file
+  * Add a service for each variant
+  * Set the build arguments
+  * Tag the image with the package type installed
+    * jfahrer/nginx:stretch-light
+    * jfahrer/nginx:stretch-full
+    * jfahrer/nginx:stretch-extras
+  * Build and push all the images
+
+## The Dockerfile
+```
+FROM debian:buster-slim
+
+RUN apt-get update \
+      && apt-get install -y nginx \
+      && rm -rf /var/lib/apt/lists/* \
+      && rm /var/log/nginx/access.log \
+      && rm /var/log/nginx/error.log \
+      && ln -s /dev/stdout /var/log/nginx/access.log \
+      && ln -s /dev/stderr /var/log/nginx/error.log
+
+CMD ["/usr/sbin/nginx", "-g", "daemon off;"]
+```