Connecting to the cluster
=========================

The access to the cluster depends on the Operating System present on your personal laptop. If you have a Linux, Unix or OSX Operating System you can use the ``ssh`` client from command line, from whichever terminal.

Specifically, to connect to the Pleiadi cluster frontend as a user with a certain username, execute:

``$ ssh <username>@pleiadi.oact.inaf.it``

For example, for the user ``pippo`` the login command is:

``$ ssh pippo@pleiadi.oact.inaf.it``

After executing the ``ssh`` command, the login can be completed inserting a password or without the need of inserting a password, if a public key created on your laptop is provided to the cluster.

#. **With the password**: insert the password provided by the cluster administrator when your user was created on the cluster. It is recommended to change the provided password at first login with the ``passwd`` command. Anyway, the password annually expires and the users can renew it with the ``passwd`` command. There are no restrictions on the password length and composition but it is recommended to choose a password made of 8 or more characters, containing numbers and both uppercase and lowercase letters.
#. **With key exchange**:

   #. Create on your laptop a public/private couple of keys, with the command ``$ ssh-keygen``, confirming the default values during the procedure. With this command, a public (``id_rsa.pub``) and a private (``id_rsa``) key are created in the ``.ssh`` directory of your laptop.
   #. Login to Pleiadi inserting the password provided by the administrator.
   #. Append the content of the ``id_rsa.pub`` key created on your laptop in the ``/home/pippo/.ssh/authorized_keys`` file.
   #. From the next login, you will be able to execute ``$ ssh pippo@pleiadi.oact.inaf.it`` without password insertion.
   
If you have a Windows Operating System on your laptop, it is recommended to use the PuTTY application (available at the website `PuTTY <http://www.putty.org>`_), to be configured as in the below figure:

.. figure:: PuTTY.png
    :align: center
    :figwidth: 500px

    Figure 1: Putty - Configuration for the access to remote clusters from computers with Windows Operating System.