This page is a bad fast google translate of the french version.

Fundamentals

The computational servers are shared and accessible to all members of the laboratory. However access is granted provided people have hpc_users group membership (associated with mailing list subscription). Ask any sysadmin to get that membership.

Some users have higher priority on servers. The list of prioritized users is in the file /etc/security/limits.conf as you can see. If you think you have the right to be in this list, contact the HPC referent for your team (or your team manager). Only teams directly involved in the financing of servers are eligible.

Some serveurs are fully shared and do not have priorities : sully and roadrunner.

Server features

All servers are installed in Ubuntu 18.04 LTS 64bit. They are cloned on the same model as the desktop workstations, thus facilitating program prototyping on clients before running on servers.

Supervision

At every moment, you can view load of computation servers for 24 hours at : http://supervision.greyc.fr.
Warning, graphs are updated every two minutes.

Best practices

Here are some common sense rules that should allow smooth experiments.

Do not start more processes (or threads) that cores on the server

Limit as possible outputs (stdout or stderr) as they slow down significantly the calculations.

Priority use the server's local disk space

It is forbidden to use the NFS service directories for I / O.

It is not recommended to use the other NFS services to make calculations with intensive needs I / O.

Do not let htop permanently because it consumes CPU control.

It is desirable to use the screen to control the console to recover in case of failure of the network connection. If you are allergic to screen, you can use nohup to minimum.

Available disk space

The servers are more disc space height and variables.

The directory / cluster / contains shared data, possibly subject to licenses (corpus). The Access Control List (ACL) to allow the access only to authorized persons rights. If you do not have access to a resource, contact the owner.

Screen cheat sheet

Useful commands to type in a normal shell (bash type):

Start screen: screen

Reconnect from another console: screen-r

Share the screen several: screen-x

Steal the screen: screen-d-r

List screen already launched: screen-ls

Inside the software screen, some interesting shortcuts:

Ctrl-a c: creation of a terminal

Ctrl-a k kill (destroy) the current terminal

Ctrl-a A: Rename the current terminal

Ctrl-a n: next terminal

Ctrl-a p: previous terminal

Ctrl-a NUM: NUM go to terminal

Ctrl-a d: off (turn the screen background software, for later retrieval)

Priority principles

The following is valid only on servers where priorities have been established:

Every user has a server running 15 default priority

Partially priority users are 10

Priority is 5

For a list of priorities for a server, look at the contents of /etc/security/limits.conf. In case of bad priority assignment, consult your reference:

Team Image: A. Lechervy

Team MAD: L. Jeanpierre.

In case of urgent need related to deadlines, priority teams, the referees are trying to better organize the distribution calculations on the server, if necessary, requesting cleaning system administrators.

Access from outside the laboratory

SSH gateways are reachable from outside the laboratory. Using the generic name gw.greyc.fr should lead you to one of them. For other servers, you will need to use a rebound per ssh gateways (proxy jump).

Staff whose laptop is managed or co-managed by DSI Campus 2 support (machines identified C301L-XXXXXX or N302L-XXXXXX) can request VPN access by contacting support. This solution is more convenient if you have to perform data transfers.

The request for VPN access to the establishment's network is to be made on the Request Management site: https://gedemande.unicaen.fr/ .

Maintenance and communication

To avoid disrupting the current experiments, the servers are restarted after asking the owners of calculation running. Communication of maintenance will only be to the HPC-users list GREYC. If you do not subscribe to this list, please make the request to your reference or an administrator if you do not have a referent.

Operation cuda

On a machine with an NVIDIA graphics card, you can run CUDA process. How to:

1. Check the status with "nvidia-smi" . This command should return information about NVIDIA graphics card(s) installed in the machine . If it is not the case, contact an administrator.
2. Edit your PATH and LD_LIBRARY_PATH to use the CUDA environment:
   1. export LD_LIBRARY_PATH=/usr/local/cuda/lib64:/usr/local/lib/:$LD_LIBRARY_PATH
   2. export PATH=/usr/local/cuda/bin:$PATH
3. Test cards :  /usr/local/cuda/extras/demo_suite/deviceQuery

Other computing resources available to GREYC members

See CRIANN.