Trac #29545: document how to use Jupyter remotely

This ticket adds this to the documentation. Namely:
{{{
ssh -L localhost:8888:localhost:8888 -t USER@REMOTE sage -n jupyter
--no-browser --port=8888
}}}
Previously discussed on [https://groups.google.com/forum/#!topic/sage-
devel/eA4LLyHP99M sage-devel].

URL: https://trac.sagemath.org/29545
Reported by: gh-mwageringel
Ticket author(s): Markus Wageringel
Reviewer(s): Matthias Koeppe

Author: Release Manager

src/doc/en/installation/launching.rst

@@ -9,13 +9,46 @@ Notebook from the command line.
 
 If you did install the Windows version or the macOS application you
 should have icons available on your desktops or launching menus. Otherwise
-you are strongly advised to create shortcuts for Sage as indicated as the end
+you are strongly advised to create shortcuts for Sage as indicated at the end
 of the "Linux" Section in :ref:`sec-installation-from-binaries`. Assuming
-that you have this shortcut, running ``sage`` in a console starts a Sage
-session. To quit the session enter ``quit`` and then press ``<Enter>``. To
-start a Jupyter Notebook instead of a Sage console, run the command
-``sage -n jupyter`` instead of just ``sage``. To quit the Jupyter Notebook
-press ``<Ctrl> + <c>`` twice in the console where you launched the command.
+that you have this shortcut, running
+
+.. CODE-BLOCK:: bash
+
+    sage
+
+in a console starts a Sage session.  To quit the session enter ``quit`` and
+then press ``<Enter>``.
+
+To start a Jupyter Notebook instead of a Sage console, run the command
+
+.. CODE-BLOCK:: bash
+
+    sage -n jupyter
+
+instead of just ``sage``. To quit the Jupyter Notebook press ``<Ctrl> + <c>``
+twice in the console where you launched the command.
+
+Using a Jupyter Notebook remotely
+---------------------------------
+
+If Sage is installed on a remote machine to which you have ``ssh`` access, you
+can launch a Jupyter Notebook using a command such as
+
+.. CODE-BLOCK:: bash
+
+    ssh -L localhost:8888:localhost:8888 -t USER@REMOTE sage -n jupyter --no-browser --port=8888
+
+where ``USER@REMOTE`` needs to be replaced by the login details to the remote
+machine. This uses local port forwarding to connect your local machine to the
+remote one. The command will print a URL to the console which you can copy and
+paste in a web browser.
+
+Note that this assumes that a firewall which might be present between server
+and client allows connections on port 8888. See details on port forwarding on
+the internet, e.g. https://www.ssh.com/ssh/tunneling/example.
+
+------------------------------------------------------------------------
 
 For further reading you can have a look at the other documents in the
 SageMath documentation at http://doc.sagemath.org/.