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General FAQS

How do I get an account?

You should apply online

How do I find the correct IP address to register for direct access?

You should not have to do this if you are logging in from (or via) a machine connected to the CNN (the Centrale Nantes Network), which is likely to be the case if the machine is in the campus. If the machine is elsewhere, and you have SSH access to a system within the CNN, then follow the procedure here. If neither of the above are true, it is necessary to register an additional IP address to allow direct SSH connection to the ICI-SC systems. Hopefully, the machine you are sitting at has a static, public IP address - please try to find out whether it does from local IT support. In any event, it requires internet access, and browsing to the site should report the public IP address from which traffic from your machine will appear to originate, and which would have to be registered in order for SSH connections to us to be accepted. Please note however that registering a dynamic or gateway address, which is implied if your machine does not have an address which is both static and public, is strongly disfavoured for reasons of security.

How to create a visualization session?

Il faut préalablement télécharger et installer TurboVNC sur votre machine.
Puis vous devez utiliser le portail pour créer une nouvelle session de visualisation.

How to compile with CUDA on a visu node et analyze afterwards the results?

Il faut allouer préalablement une partie de la ressources de visualisation pour exécuter une session ssh sur ce noeud.

$ salloc -N 1 -n 1 -p visu
$ srun hostname
$ ssh <vizX>

How can I get shell prompts in interactive mode?

# srun --pty bash -i

Srun's –pty option runs task zero in pseudo terminal mode. Bash's -i option tells it to run in interactive mode (with prompts).

What is the difference between the sbatch and srun commands?

The srun command has two different modes of operation. First, if not run within an existing job (i.e. not within a Slurm job allocation created by salloc or sbatch), then it will create a job allocation and spawn an application. If run within an existing allocation, the srun command only spawns the application. For this question, we will only address the first mode of operation and compare creating a job allocation using the sbatch and srun commands.

The srun command is designed for interactive use, with someone monitoring the output. The output of the application is seen as output of the srun command, typically at the user's terminal. The sbatch command is designed to submit a script for later execution and its output is written to a file. Command options used in the job allocation are almost identical. The most noticable difference in options is that the sbatch command supports the concept of job arrays, while srun does not. Another significant difference is in fault tolerance. Failures involving sbatch jobs typically result in the job being requeued and executed again, while failures involving srun typically result in an error message being generated with the expectation that the user will respond in an appropriate fashion.

Why won't my job start?

Why won't my job submit?

How do external collaborators get an account?

How many processors (or other resources) should I request per job?

How many resources can I use?

Why am I not getting job notification emails? How do I make them stop?

How do I set up SSH keys for passwordless login?

How do I choose a specific MPI implementation?

How do I limit the amount of memory that my program uses?

supercomputer/liger/faqs/general.txt · Last modified: 2016/05/18 14:09 by