[Beowulf] password-less "rsh"

[Martin Siegert]

Hi Pete,

On Sat, Jul 30, 2005 at 12:34:23AM +0100, Pete Nevill wrote:
> I am trying to put a cluster together but seem to have fallen at the
> first hurdle. A key part of the cluster set up is for the master node to
> be able to communicate and run processes on the slave nodes. One way I
> have seen to do this is to use the "rsh" command. Unfortunately I am
> unable to get this to work in a "password-less" way, actually cannot
> connect one node to the other using "rsh" without getting a connection
> refused or unable to authenticate 
> "Trying krb4 rlogin...
> krb_sendauth failed: You have no tickets cached"
> 
> Security is not an issues as none of the nodes will not be connected to
> the Internet. only the master node for which the slave nodes do not need
> to logon to. I have change "disabled = no" in the /etc/xinted.d/rsh and
> telnet files. There is no firewall up, host.deny is empty and so is
> hosts.allow. I have added the machine names to .rhosts and hosts.equiv
> but still no joy. Any help or advice would be much appreciate. I am
> pulling my hair out over what should be a very simple thing.
> 
> Thanks,
> 
> Pete.
> P.S. I am using 2.6.11-1.1369_FC4

While I am not absolutely sure what the problem is there are two indications
of what may go wrong:

you seem to be using
1) the kerberos version of "rsh"
2) you seem to be using rsh in the form "rsh <hostname>" instead of
   "rsh <hostname> <command>"

ad 1) try to find where the non-kerberos rsh is (usually in /usr/bin)
and make sure that it appears in the PATH before the kerberos version.
ad 2) "rsh <hostname>" is actually the same as "rlogin <hostname>".
Thus, in order to get that to work you would need to enable the rlogin
protocol in /etc/xinetd.d/rlogin. But you do not need this for MPI, etc.
(you also do not need telnet, thus you could leave that disabled
as well). What you do need to get working is "rsh <hostname> <command>".

I hope this helps.

Cheers,
Martin

-- 
Martin Siegert
Head, HPC at SFU
WestGrid Site Manager
Academic Computing Services                        phone: (604) 291-4691
Simon Fraser University                            fax:   (604) 291-4242
Burnaby, British Columbia                          email: siegert at sfu.ca
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