5.6.3 Autofs: The Automounter

		OPTIONS

		Options control timeouts, status reports, output flushing, etc. Options may be entered with one -hyphen or two -hyphens and they may be abbreviated as long as they are unambiguous.

		Detailed information about the options may be found in the online manual page.

		EXAMPLES

		Set the default list of remote processors to the contents of a file export PRSH_HOSTS='cat /var/run/bnodes-up'

		Ensure that we have a directory on every node's /scratch:

		prsh -- mkdir --parent /scratch/johns/tmp

		Kill the program amok (perhaps an MPI or PVM process) that is running out of control.

		prsh -- killall amok

		Ask every remote processor to touch a unique file in your home directory. This is a fairly severe test that network services, including NFS and rsh are intact between the remote nodes and the host node. Nodes that respond with OK are probably completely operational. Type this command on a single line.

		prsh --prepend -ssh --status -- touch $HOME/.checknodes/\'uname     --nodename\'

		ENVIRONMENT

		Any switches in the PRSH_OPTIONS environment variable will be used before the command line arguments. The environment variable PRSH_HOSTS is used as a list of hostnames only if no hostnames are explicitly provided on the command line.

		SEE ALSO

		rsh(1), ssh(l)

		6.5 Defending the Pack: Security Strategies

		After the number of computers connected to the Internet exploded in the mid '90s, it became impossible to attach a computer to a network without paying some attention to preventive security measures. The situation is no different with Beowulf clusters, and is even more important, because making a Beowulf accessible via the