Getting started
===============

This tutorial should be adequate for users not familiar
with the Slurm Workload Manager. All concepts will be introduced
gradually. However, intermediate knowledge of the Linux command line
is required to fully understand the described concepts.

Logging in into the cluster
---------------------------

The cluster contains a single point of entry, that is the ``entropy`` login node.

The server is accessible from the Faculty's internal network and from the Internet.

.. warning::
  As the login node is exposed to the wild wild Internet,
  a prohibitive firewall is configured. Additionally, any excessive login attempts
  will be blocked by a specialized software.

The only one way to log in into the cluster is by using the **SSH keys**;
password authentication is disabled. 

.. code-block:: shell
   :linenos:

   ssh cluster_user@entropy.mimuw.edu.pl

Home directory and disk quota
-----------------------------

Each user of the **entropy** cluster has a home directory located on the login node.
The ``/home`` system is ``RAID5`` and thus is tolerant of a failure of one HDD.
Currently, there is no backup of the user's data.

.. warning::
   Currently, we cannot provide any backup of the ``/home`` disk array. Thus, each
   user should backup important files and results outside of the cluster.

Each user has a limited **quota** on the cluster login node. The quota is enabled
for the ``/home`` filesystem.

* The **quota** value for students and other users is 60 GB.
* The **quota** value for Faculty's staff is 120 GB.

Each user can check the disk usage:

.. code-block:: shell
   :linenos:

   $ entropy_account_info 
   
      ____________
     < Disk quota >
      ------------
       \
        \   \_\_    _/_/
         \      \__/
                (oo)\_______
                (__)\       )\/\
                    ||----w |
                    ||     ||
   
   +----------------+----------+-----------+
   | Mountpoint     | Used     | Limit     |
   +----------------+----------+-----------+
   | /home          | 16K      | 60G       |
   +----------------+----------+-----------+

/home NFS
---------

``/home`` partition is available on each compute node through the NFS share.
All results from computations should be written here or to one of local
filesystems.

.. warning::
   Please **do not** run any computations on the login node! This machine serves
   as an entry point to the cluster and hosts users' home directories, Slurm deamons,
   monitoring system, etc.

   If results of computations (or any intermediate steps) are large, please write them
   to one of available local partitions and then copy them to your home directory.