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ssh#

Two key points when using the supercomputer:

  1. We access the computers remotely with our terminal

  2. Slurm is used to manage jobs on the cluster

What is ssh?#

To login remotely to a supercomputer, we use the command ssh on the terminal. This is short for secure shell protocol and can take a few arguments. The syntax is ssh [username]@ssh.server.example.edu.

First, open your terminal, and follow the directions for Oscer or Pete SSH. Change the [username] part, to the username you created!!

What is Slurm?#

Since high-performace computing centers are composed of many parts (CPU, GPU, RAM, SSD, HDD, etc.), involving many different users (biological science, machine learning, etc.) with different needs. They require a job scheduling and resource management system. One system is Slurm.

Slurm is like a traffic cop for computers. It’s a software system used in big computer clusters, like those in data centers or supercomputers. Slurm helps manage and allocate the computing resources, like processors and memory, to different tasks or jobs that people want to run on the cluster.

Imagine a busy intersection where the traffic cop directs cars to different lanes or tells them when to go. Slurm does something similar but for computer tasks, making sure they don’t crash into each other and efficiently use the available resources, so everything runs smoothly. It helps coordinate and schedule who gets to use the computers and when.

For us, the users, some key points when using Slurm are:

  1. Job Submission/Management

  2. Resource Allocation/Utilization

  3. Scripting and Automation

Accessing the HPC#

Remote Login#

Accessing the supercomputer can be done on your laptop, in the comfort of your bed. The command is ssh, which stands for “Secure Shell protocol”.

It has the following format:

ssh username@hostname

Where,

  1. username is the username (whatever you made when applying for the account)

  2. @ is always between username and hostname

  3. hostname is the name and IP address of the supercomputer

Example For my username, van, the command would be:

ssh van@hostname

What is the hostname?#

It depends on the computing center. In Oklahoma, you can access Oscer (schooner.oscer.ou.edu) or Pete (pete.hpc.okstate.edu) by:

ssh username@schooner.oscer.ou.edu 

ssh username@pete.hpc.okstate.edu

Task: Accessing the HPC#

Try logging into one of the supercomputer. Change the hostname to the pete.hpc.okstate.edu or ``schooner.oscer.ou.edu`.

My username is van, so logging in looks like this:

ssh van@schooner.oscer.ou.edu 

ssh van@pete.hpc.okstate.edu

Note

On the first login attempt, you will get the following prompt:

The authenticity of host 'pete.hpc.okstate.edu' cannot be established.
 DSA key fingerprint is 01:23:45:67:89:ab:cd:ef:ff:fe:dc:ba:98:76:54:32:10.
 Are you sure you want to continue connecting (yes/no)?

Answering yes to the prompt will cause the session to continue, and the host key is stored in the local system’s known_hosts file. This is a hidden file, stored by default in a hidden directory, called /.ssh/known_hosts, in the your home directory. Once the host key has been stored in the known_hosts file, the client system can connect directly to that server again without need for any approvals.

Answer yes by typing into your terminal. This will only happen on the first login!

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