Install
=======

Single-User
___________

Once you have downloaded the Digichem archive, the next step is to upload it to your computational cluster.
Place the archive in the location where you want to install Digichem, which can be anywhere in your home directory.
Digichem requires `ca.` 800 MB of file space to install.

Once uploaded, unpack the archive with tar:

.. code-block:: console

    $ tar -xzf digichem.*.tar.gz
    
And then run the install script:

.. code-block:: console

    $ digichem/_internal/install.sh
    
If all goes well, the program version will be printed to the console:

.. code-block:: console

    Creating links...
    Checking Digichem installation (this may take a few minutes)...
    6.0.0
    Installation complete.
    
Digichem is now ready to use, and the archive can be safely deleted:

.. code-block:: console

    $ rm digichem.*.tar.gz
    
Next, :ref:`configure <setup>` Digichem so it knows which computational backends are available, and then you're ready to begin submitting calculations!


Multi-User
__________

If you are installing Digichem so it can be used by multiple users,
make sure to unpack the archive to a shared file location where each of the users has (at least) read access.

The archive can be unpacked with tar:

.. code-block:: console

    $ tar -xzf digichem.*.tar.gz
    
Which will unpack the program to a folder simply called 'digichem'

.. code-block:: console

    $ ls
    digichem.6.0.0.CentOS-Stream-8.tar.gz  # The name of this file will differ depending on which version you downloaded.
    digichem                               # This directory contains the new digichem installation.
    
Once unpacked, the archive can be deleted:

.. code-block:: console

    $ rm digichem.6.0.0.CentOS-Stream-8.tar.gz
    
The program binaries are placed immediately inside the `digichem` folder:

.. code-block:: console

    $ ls digichem
    digichem    # Main digichem executable.
    _internal   # Binaries and libraries.
    LICENSE     # Licensing information.
    openprattle # Bundled Openprattle binaries and libraries
    oprattle    # Bundled Openprattle executable (used for file interconversions).

Each installation contains a bundled copy of `Openprattle <https://github.com/Digichem-Project/openprattle>`_ 
, which is free and open-source software.
    
To make the program available to users, the install location simply needs to be added to their ``$PATH`` variable.
You can either configure this yourself (for example, in ``/etc/bash.bashrc``), or each user can run the install script
to setup the necessary links.

The install script is located at `digichem/_internal/install.sh`. Thus if the Digichem folder was installed to:
``/opt/digichem/``, the command for each user would be ``/opt/digichem/_internal/install.sh``.

In a multi-user installation, Digichem will parse config files from ``/etc/digichem{VERSION}`` (where ``{version}`` is the major version number, 
for example ``6``), which will be shared by all users. Each individual user can also set their own config options at ``~/.config/digichem{VERSION}``,
the same as for a single-user installation.

Proceed next to the :ref:`setup <setup>` step to configure Digichem ready for use.

Upgrading From An Old Version
_____________________________

An older version of Digichem can be upgraded by simply unpacking the new archive on top of the old installation folder.
For example, if Digichem was previously installed to ``/software/digichem``, place the archive in the ``/software/`` folder,
and unpack with tar:

.. code-block:: console

    $ tar -xzf digichem.*.tar.gz
    
The files from the old installation will be replaced with the new version.