Using Secure Socket Handler (SSH) in the CAD Compute Cluster
In this document, a “$>” symbol refers to a LINUX prompt in a terminal window.
Secure Socket Handler (SSH) is a form of security granted to users in this cluster. A passcode is generated by a small script, and placed on each node (login, compute) to permit intra-cluster/inter-nodal communication during a user’s simulation runs.
The utility setsshkey is used as a kind of password checking on nodes (SSH security).
- Found under /home/scripts/ (top-level directory)
Figure 2. The location of the setsshkey script.
To set up SSH keys in advance of your first simulation run, type in a terminal window:
When prompted, do not use a passphrase, and leave the result in the default directory. To see if an SSH key has been properly installed, type:
$> ssh uwmhpc04
A user should then be logged into that node, if the SSH permissions are set properly. This uses the fourth compute node as an example, though any uwm* node should be accessible.Use a ‘logout’ command to exit the node login.
Message Passing Interface (MPI) Software in the CAD Compute Cluster: ANSYS
A Message Passing Interface (MPI) is an application bundled with ANSYS. It handles functions that enable parts of a parallel program to communicate at a high-level with the underlying mechanisms of the host cluster, to perform such tasks as launching jobs, disk input and output, and exchanging information between distributed memories. Two flavours of MPI are bundled with ANSYS: Intel- and IBM-based. The Intel version is the default.
When ANSYS has been loaded:
$> module load ansys
.. it is possible to test MPI function using the following utility command:
$> mpitest (Intel-based version)
$> mpitest -ibmmpi (IBM-based version)
The output will be written to your screen as shown in Figure 3 and an mpitest.out file will be written to your working directory.
Figure 3. Testing the Message Passing Interface software for both Intel and IBM versions.
To see if the MPI environment variable has been set, type the command:
$> env (for all variable names)
$> env |grep –i mpi (to isolate your search to the MPI environment variable MPI_ROOT)