Subject: Re: [vserver] Understanding localhost
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Fri, 1 May 2009 23:34:08 +0200

On Fri, May 01, 2009 at 04:48:12AM -0400, John A. Sullivan III wrote:
> Hello, all.  I'd like to confirm that I understand the way vserver 2.3
> is handling localhost and the loopback address.

> Am I correct to understand that, unlike earlier version, the default
> kernel compilation makes it safe to use 127.0.0.1 on a guest? That is,
> each one is uniquely mapped and does not interfere with the host
> listening in 127.0.0.1? We can thus set our /etc/hosts files to use:
> 127.0.0.1 localhost localhost.localdomain etc . . .?

> However, is it also true that daemon bindings to localhost will still be
> made to the address in /etc/vservers/<guest>/interfaces/0 and will not
> include 127.0.0.1 unless explicitly bound?

> I ask because we were delighted to realize we could simplify our zimbra
> installation by leaving /etc/hosts at 127.0.0.1 for localhost.  We then
> started retrofitting our other servers to do the same.  Some of our
> servers communicate with sshd on 127.0.0.1.  We had changed the
> configuration files to bind them to the non-loopback address, e.g.,
> 192.168.1.10 because of our old understanding of 127.0.0.1.  We also
> changed sshd_config by removing the ListenAddress 192.168.1.10 so that
> it goes back to the default of binding to all interfaces.

> This broke those applications.  When we do a netstat -tln on the vserver
> guests, it shows sshd listening only on 192.168.1.10 (as an example) and
> not 0.0.0.0.  

if you disable the single IP special casing, this
will change to the expected behaviour ...

best,
Herbert

> That's fine and we can accommodate it by leaving our
> settings as they were but I wanted to make sure I hadn't missed
> something.  Thanks - John
> -- 
> John A. Sullivan III
> Open Source Development Corporation
> +1 207-985-7880
> jsullivan@opensourcedevel.com
> 
> http://www.spiritualoutreach.com
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