Option #3 -- Ubuntu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


If you are using the Virtual Computer, you can skip this step.

Using the instructions below, CODAS installation and CODAS
processing has been thoroughly tested with 20.04.  It may work with newer
versions.

Although you can install regular
`ubuntu desktop <http://www.ubuntu.com/download/desktop>`_
we recommend `Xubuntu <http://xubuntu.org>`__, because it
has a simpler desktop environment, which we find easier to use.  We use it for
all of our Linux installations including our UHDAS machines at sea and our
Virtual Computer.


**(1) Download and install an Ubuntu version.**

    Download and install  `Xubuntu <http://xubuntu.org>`_

**(2) Boot the new system, log in and connect to the network.**

    - install the "Synaptic Package Manager".  Type

::

      sudo apt-get install synaptic

Using ``sudo`` allows a regular user to run one command with
administrative privileges (as "root").  You must type your
own password to get a "sudo" command to run.

Synaptic is a graphical tool to manage software packages
on the computer.  The example below uses a command-line
interface but if something does not work (eg. you want to add
a package to improve your virtual machine) you
can use Synaptic to try to identify the new name.

**(3) Install various additional external packages**

The Xubuntu 20.04 installation already has these

- gcc (C-compiler)
- python 3.8

..  NOTE:: We use only Python 3, and our code is no longer compatible with
    Python 2.

Install additional required packages by typing::

    sudo apt-get install ipython3
    sudo apt-get install python3-dev
    sudo apt-get install mercurial
    sudo apt-get install python3-matplotlib
    sudo apt-get install python3-mpltoolkits.basemap
    sudo apt-get install python3-netcdf4
    sudo apt-get install python3-qtpy
    sudo apt-get install python3-qtconsole

To get ready for the next step, edit your user shell startup file (typically
``.bashrc``) to prepend ``/usr/local/bin`` to your ``PATH`` environment variable, if
it isn't already there.  As a quick way to check your current ``PATH``, use::

    printenv PATH

Now proceed to the :ref:`CODAS-specific <CODAS-packages>`
parts of the installation.