From agrajag@linuxpower.org Thu Mar  8 12:56:30 2001
Date: Thu, 8 Mar 2001 05:27:13 -0800
From: Jag <agrajag@linuxpower.org>
To: beowulf@beowulf.org
Subject: Re: Scyld and resolv library

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On Thu, 08 Mar 2001, Carlos J. Garca Orellana wrote:

> Hello,
> 
> I'm trying to start DNS resolver in nodes.
> I've created a hosts, host.conf and resolv.conf files in nodes, but, DNS
> doesn't work.
> 
> Not even, names in hosts file can be resolutes.

It's debatable wether letting nodes do this resolving is the 'right
thing', however I will assume that you have an application that's messed
up enough that it needs it.

By default, Scyld slave nodes have their nsswitch.conf setup so that
they only do host lookups through beonss (referenced as 'bproc' in the
nsswitch.conf).  This will resolve 'master' to the internal ip of the
master node, 'self' to get your own IP, '.-1' to get the master node
again, '.0' to get node zero, '.1' to get node one, and so on.  It also
reverses these so that the ip of a node (or the master node's internal
IP address) will resolve to '.<node number>' like above.   If you're
just wanting smiliar functionality to this, then you don't have to worry
about setting up dns and the hosts file.

If you're wanting more than this, you're talking about things that
theorectically shouldn't be on a beowulf cluster (like ipmasq on the
head node to get out).  However, for the /etc/hosts and dns resolution,
I'll tell you that the file you need to also look at is
/etc/nsswitch.conf


Jag

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From newt@scyld.com Thu Mar  8 12:56:49 2001
Date: Thu, 8 Mar 2001 11:41:00 -0500 (EST)
From: Daniel Ridge <newt@scyld.com>
To: Jag <agrajag@linuxpower.org>
Cc: beowulf@beowulf.org
Subject: Re: Scyld and resolv library

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On Thu, 8 Mar 2001, Jag wrote:

> On Thu, 08 Mar 2001, Carlos J. Garca Orellana wrote:

> > Hello, > > I'm trying to start DNS resolver in nodes. > I've created
> a hosts, host.conf and resolv.conf files in nodes, but, DNS > doesn't
> work. > > Not even, names in hosts file can be resolutes.

<SNIP>

Jag's discussion about local name service on Scyld was exactly right.

If you wish to create a permanently different nsswitch.conf, edit
/usr/lib/beoboot/bin/node_up to generate the contents that you want.

I believe this also means that the DNS resolver library has to be
installed in /lib on each node (as the NSS libraries are usually linked
in by dlopen() rather than by the dynamic linker).

Regards,
	Dan Ridge	
	Scyld Computing Corporation


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