Why no rlogin to nodes?

[Walt Dabell]

----- Original Message ----- 
From: "Robert G. Brown" <rgb at phy.duke.edu>

> On Thu, 12 Oct 2000, Daniel Ridge wrote:

> > Run Scyld Beowulf! Our nodes don't even have inetd -- let alone
> > rsh, telnet, or ftp daemons!

> To add just a teeny bit to this, since your "beowulf" could be more of a
> "cluster supercomputer" with some nodes acting as workstations (like
> ours) which makes just running Scyld Beowulf a bit tricky, from what
> Erik told me on Saturday at ALSC -- EVEN if you cannot run SB, EVEN if
> you don't even have "nodes" but instead have a bunch of PC's running
> linux in folks' offices and want to run e.g. PVM or MPI calculations
> spread out across them:

So are you saying that I _SHOULD_ run SB? I'm not now, and hadn't
intended to... There would have to be a monumental reason to switch
at this point. But for the future cluster... 

> You do not (and should not) run rshd, rlogind, telnetd and ftpd.  The
> only service a typical workstation needs to offer these days to enable
> just about all the kinds of incoming access one requires to support
> parallel calculations, remote logins, remote file copies (bidirectional)
> and so forth is sshd.  sshd replaces rshd (but is run standalone, not

Doesn't ssh have some extra overhead? I assume too that you
were making that recommendation assuming that I was not running
a dedicated cluster. Current and future clusters sit behind a mother
node, future also behind a firewall. Is there an advantage to running
ssh on such a cluster? I assume not?

Thanks for all the input!

     Walt Dabell  302-831-1499  walt at bartol.udel.edu
Computer Facilities Manager - Bartol Research Institute
                     University of Delaware