CIS Computing & Information Services

Getting Started

This guide assumes you have an Oscar account. To request an account see create an account

OSCAR

Oscar is the shared compute cluster operated by CCV.

Oscar runs the Linux RedHat7 operating system. General Linux documentation is available from The Linux Documentation Project. We recommend you read up on basic Linux commands before using Oscar.

It has two login nodes and several hundred compute nodes. When users log in through SSH, they are first put on one of the login nodes which are shared among several users at a time. You can use the login nodes to compile your code, manage files, and launch jobs on the compute nodes. Running computationally intensive or memory intensive programs on the login node slows down the system for all users. Any processes taking up too much CPU or memory on a login node will be killed. Please do not run Matlab on the login nodes.

What username and password should I be using?

  • If you are at Brown and have requested a regular CCV account, your Oscar login will be authenticated using your Brown credentials itself, i.e. the same username and password that you use to login to any Brown service such as "canvas". We have seen login problems with the Brown credentials for some users so accounts moved to the Red Hat 7 system after September 1st 2018 can also log in to Red Hat 7 with their CCV password.

  • If it is a temporary guest account (e.g. as part of a class), you should have been provided with a username of the format "guestxxx" along with a password.

  • If you are an external user, you will have to get a sponsored ID at Brown through the department with which you are associated, before requesting an account on Oscar. Once you have the sponsored ID at Brown, you can request an account on Oscar and use your Brown username and password to login.

Connecting to Oscar for the first time

As of 9am September 24th 2018 the Red Hat 7 system will be the default login from ssh.ccv.brown.edu

To log in to Oscar you need Secure Shell (SSH) on your computer. Mac and Linux machines normally have SSH available. To login in to Oscar, open a terminal and type

ssh <username>@ssh.ccv.brown.edu

Windows users need to install an SSH client. We recommend PuTTY, a free SSH client for Windows. In PuTTY, use <username>@ssh.ccv.brown.edu or <username>@ssh4.ccv.brown.edu for the Host Name.

The first time you connect to Oscar you will see a message like:

The authenticity of host 'ssh.ccv.brown.edu (138.16.172.8)' can't be established.
RSA key fingerprint is SHA256:Nt***************vL3cH7A.
Are you sure you want to continue connecting (yes/no)? 

You can type yes . You will be prompted for your password. Note nothing will show up on the screen when you type in your password, just type it in and press enter. You will now be in your home directory on Oscar. In your terminal you will see a prompt like this:

[mhamilton@login004 ~]$ 

Congratulations, you are now on one of the Oscar login nodes.

Note: Please do not run computations or simulations on the login nodes, because they are shared with other users. You can use the login nodes to compile your code, manage files, and launch jobs on the compute nodes.

Changing Passwords

This section is only relevant for guest accounts as regular accounts will simply use their Brown password.

To change your Oscar login password, use the command:

$ passwd

You will be asked to enter your old password, then your new password twice.

Password reset rules:

  • minimum length: 8 characters
  • should have characters from all 4 classes: upper-case letters, lower-case letters, numbers and special characters
  • a character cannot appear more than twice in a row
  • cannot have more than 3 upper-case, lower-case, or number characters in a row
  • at least 3 characters should be different from the previous password
  • cannot be the same as username
  • should not include any of the words in the user's "full name"

File system

Users on Oscar have three places to store files.

  • home
  • scratch
  • data

Note guest and class accounts may not have a data directory. Users who are members of more than one research group may have access to multiple data directories.

To see how much space you have you can use the command myquota. Below is an example output

                   Block Limits                              |           File Limits              
Type    Filesystem           Used    Quota   HLIMIT    Grace |    Files    Quota   HLIMIT    Grace
-------------------------------------------------------------|--------------------------------------
USR     home               8.401G      10G      20G        - |    61832   524288  1048576        -
USR     scratch              332G     512G      12T        - |    14523   323539  4194304        -
FILESET data+apollo        11.05T      20T      24T        - |   459764  4194304  8388608        -

A good practice is to configure your application to read any initial input data from ~/data and write all output into ~/scratch. Then, when the application has finished, move or copy data you would like to save from ~/scratch to ~/data. For more information on which directories are backed up and best practices for reading/writing files, see Managing Files. You can go over your quota up to the hard limit for a grace period (14days). This grace period is to give you time to manage your files. When the grace period expires you will be unable to write any files until you are back under quota.


Software modules

CCV uses the PyModules package for managing the software environment on OSCAR. To see the software available on Oscar use the command module avail. The command module list shows what modules you have loaded. Below is an example of checking which versions of the module 'workshop' are available and loading a given version.

[mhamilton@login001 ~]$ module avail workshop
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ name: workshop*/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
workshop/1.0  workshop/2.0  
[mhamilton@login001 ~]$ module load workshop/2.0
module: loading 'workshop/2.0'
[mhamilton@login001 ~]$ 

For a list of all PyModule commands see Software Modules. If you have a request for software to be installed on Oscar, email support@ccv.brown.edu.


Using a Desktop on Oscar

You can connect remotely to a graphical desktop environment on Oscar using CCV's VNC client. The CCV VNC client integrates with the scheduling system on Oscar to create dedicated, persistent VNC sessions that are tied to a single user.

Using VNC, you can run graphical user interface (GUI) applications like Matlab, Mathematica, etc. while having access to Oscar's compute power and file system.

For download and installation instructions, click here.


Running Jobs

You are on Oscar's login nodes when you log in through SSH. You should not (and would not want to) run your programs on these nodes as these are shared by all active users to perform tasks like managing files and compiling programs.

With so many active users, a shared cluster has to use a "job scheduler" to assign compute resources to users for running programs. When you submit a job (a set of commands) to the scheduler along with the resources you need, it puts your job in a queue. The job is run when the required resources (cores, memory, etc.) become available. Note that since Oscar is a shared resource, you must be prepared to wait for your job to start running and it can't be expected to start running straight away.

Oscar uses the SLURM job scheduler. Batch jobs is the preferred mode of running programs, where all commands are mentioned in a "batch script" along with the required resources (number of cores, wall-time, etc.). However, there is also a way to run programs interactively.

For information on how to submit jobs on Oscar, see Running Jobs. There is also extensive documentation on the web on using SLURM. For instance, here is a quick start guide.


Where to get help