QLogic OFED+ Host Software User Guide, Rev. B

3–TrueScale Cluster Setup and Administration
Host Environment Setup for MPI
Configuring for ssh
Running MPI programs with the command mpirun on an TrueScale cluster
depends, by default, on secure shell ssh to launch node programs on the nodes.
In QLogic MPI, mpirun uses the secure shell command ssh to start instances of
the given MPI program on the remote compute nodes without the need for
interactive password entry on every node.
To use ssh, you must have generated Rivest, Shamir, Adleman (RSA) or Digital
Signal Algorithm (DSA) keys, public and private. The public keys must be
distributed and stored on all the compute nodes so that connections to the remote
machines can be established without supplying a password.
You or your administrator must set up the ssh keys and associated files on the
cluster. There are two methods for setting up ssh on your cluster. The first
method, the shosts.equiv mechanism, is typically set up by the cluster
administrator. The second method, using ssh-agent, is more easily
accomplished by an individual user.
NOTE:
• rsh can be used instead of ssh. To use rsh, set the environment
variable MPI_SHELL=rsh. See “Environment Variables” on page 4-20 for
information on setting environment variables. Also see “Shell Options”
on page A-6 for information on setting shell options in mpirun.
• rsh has a limit on the number of concurrent connections it can have,
typically 255, which may limit its use on larger clusters.
Configuring ssh and sshd Using shosts.equiv
This section describes how the cluster administrator can set up ssh and sshd
through the shosts.equiv mechanism. This method is recommended, provided
that your cluster is behind a firewall and accessible only to trusted users.
“Configuring for ssh Using ssh-agent” on page 3-32 shows how an individual user
can accomplish the same thing using ssh-agent.
The example in this section assumes the following:
• Both the cluster nodes and the front end system are running the openssh
package as distributed in current Linux systems.
• All cluster end users have accounts with the same account name on the
front end and on each node, by using Network Information Service (NIS) or
another means of distributing the password file.
• The front end used in this example is called ip-fe.
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