docs: fix broken links and formatting errors

docs/source/admin/upgrading.rst

@@ -44,7 +44,9 @@ Before doing an upgrade, it is critical to back up:
 
 #. Your JupyterHub database (SQLite by default, or MySQL / Postgres if you used those). 
    If you use SQLite (the default), you should backup the ``jupyterhub.sqlite`` file.
+
 #. Your ``jupyterhub_config.py`` file.
+
 #. Your users' home directories. This is unlikely to be affected directly by
    a JupyterHub upgrade, but we recommend a backup since user data is critical.
 

docs/source/getting-started/config-basics.md

@@ -77,8 +77,8 @@ jupyterhub --Spawner.notebook_dir='~/assignments'
 ## Configure for various deployment environments
 
 The default authentication and process spawning mechanisms can be replaced, and
-specific [authenticators](./authenticators-users-basics) and
-[spawners](./spawners-basics) can be set in the configuration file.
+specific [authenticators](authenticators-users-basics) and
+[spawners](spawners-basics) can be set in the configuration file.
 This enables JupyterHub to be used with a variety of authentication methods or
 process control and deployment environments. [Some examples](../reference/config-examples),
 meant as illustrations, are:

docs/source/reference/config-sudo.md

@@ -6,7 +6,7 @@ Only do this if you are very sure you must.
 
 ## Overview
 
-There are many [Authenticators](./authenticators-users-basics) and [Spawners](./spawners-basics) available for JupyterHub. Some, such
+There are many [Authenticators](../getting-started/authenticators-users-basics) and [Spawners](../getting-started/spawners-basics) available for JupyterHub. Some, such
 as [DockerSpawner](https://github.com/jupyterhub/dockerspawner) or [OAuthenticator](https://github.com/jupyterhub/oauthenticator), do not need any elevated permissions. This
 document describes how to get the full default behavior of JupyterHub while
 running notebook servers as real system users on a shared system, without