Product specifications

5 – Detailed Descriptions of Command LineTools

Basic Setup and Administration Tools

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Fast Fabric provides additional flexibility in the translation between IPoIB and

management network hostnames. Refer to appendix C for more information.

Setup_ssh provides an easy way to create ssh keys and distribute them to the

hosts in the cluster. Many of the Fast Fabric tools (as well as many versions of

MPI) require ssh be set up for password-less operation. Therefore, setup_ssh

is an important setup step.

This tool also sets up ssh to the local host and the local hosts IPoIB name. This

capability is required by selected Fast Fabric commands and may be used by

some applications (such as MPI).

Setup_ssh has two modes of operation. The mode is selected by the presence

or absence of the -C option. Typically, setup_ssh will first be run without the

-C option, then it may later be run with the -C option.

Initial key exchange

When run without the -C option, setup_ssh will perform the initial key exchange

and enable password-less ssh and scp. The key exchange can be accomplished

using ssh and scp (in a password prompting manner) via the -s option or using

password-less rsh and rcp (omitting the -s option).

The preferred way to use setup_ssh for initial key exchange is with the -s

and -S options. This requires all hosts have been configured with the same

password for the specified "user" (typically root). In this mode the password

will be prompted for once and then ssh and scp are used in conjunction with that

password to complete the setup for the hosts. Use in this manner also avoids

the need to setup rsh/rcp/rlogin (which can be a security risk).

If -s is used without the -S option, the user will be prompted by ssh and scp for

each host as they are setup. There will be multiple prompts per host. For a

handful of hosts this is manageable, however for a significant number of hosts

this can become cumbersome. Therefore, the -S option is recommended in this

case.

If the -s option is not specified, rsh and rcp will be used to perform the ssh key

exchange. This requires password-less rcp and rlogin be enabled on each host

(check_rsh can perform verification).

Setup_ssh will configure password-less ssh/scp for both the management

network and IPoIB. Typically, the management network will be used for Fast

Fabric while IPoIB will be used for MPI and other applications. If IPoIB is not yet

running (for example, during initial cluster installation IB software will not yet be

installed on all the hosts), the -i option can be specified with an empty string:

setup_ssh -i ''

This will cause the last part of the setup of ssh for IPoIB to be skipped.

Refreshing local systems known hosts