[Beowulf] problem of mpich-1.2.7p1

[Mark Hahn]

> In MPICH2 you need to establish passwordless ssh (not rsh!)
> connection across your machines.

it should be said that mpich2 doesn't strictly require this.
all mpi flavors can operate with other spawning methods - 
some have hooks to be spawned by the resource manager, for instance, 
which bypasses ssh/rsh type access.

> In OpenMPI you also need to establish passwordless ssh connection

same for OpenMPI: doesn't actually require passwordless ssh.

but if you do want passwordless ssh, IMO the only sane solution is to 
configure hostbased trust.  having an unencrypted private key in your 
home directory is hideous (moral equivalent of putting your password 
in a file, in the clear...)