Fix requirements topic document

docs/topic/requirements.rst

@@ -0,0 +1,29 @@
+.. _requirements:
+
+===================
+Server Requirements
+===================
+
+Operating System
+================
+
+We require using Ubuntu 18.04 as the base operating system for your server.
+
+Root access
+===========
+
+Full ``root`` access to this server is required. This might be via ``sudo``
+(recommended) or by direct access to ``root`` (not recommended!)
+
+External IP
+===========
+
+An external IP allows users on the internet to reach your JupyterHub. Most
+VPS / Cloud providers give you a public IP address along with your server. If
+you are hosting on a physical machine somewhere, talk to your system administrators
+about how to get HTTP traffic from the world into your server.
+
+CPU / Memory / Disk Space
+=========================
+
+See how to ref:`howto/resource-estimation`