Subject: Re: [vserver] Understanding localhost
From: "John A. Sullivan III" <jsullivan@opensourcedevel.com>
Date: Fri, 01 May 2009 09:19:32 -0400

On Fri, 2009-05-01 at 07:24 -0400, John A. Sullivan III wrote:
> On Fri, 2009-05-01 at 04:48 -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.  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
> Hmm . . . we're noticing this showing up in our Zimbra installation,
> too.  It all went splendidly well despite the hard coded installation
> routine use of 127.0.0.1.  However, when it tried to access its java
> engine on localhost, it failed.  It looks like almost all (but not quite
> all) services are bound to the non-loopback IP address.  I'm getting
> ready to change the localhost entry back to the non-loopback address now
> that the installation is complete but thought I had better check with
> the more knowledgeable folks on the list.  Thanks - John
As a follow up to anyone integrating vserver and zimbra, I deleted the
entire vserver guest and started over.  This time, I use an /etc/hosts
file with:
        127.0.0.1 localhost.localdomain localhost
        192.168.x.x guestname.domain guestname
There were still a few glitches in the installation such as needing a
symbolic link named /etc/syslog.conf to /etc/rsyslog.conf - nothing to
do with vserver.
As expected, the calls to build the documentation via the java engine
failed but the installation was successful.
I then stopped the vserver and edited the guest's /etc/hosts to now
read:
192.168.x.x localhost.localdomain localhost guestname.domain guestname
The system now starts without error.  I was able to manually create the
documentation and all services are bound to 192.168.x.x except 10024
which is, I believe, amavisd and can be fixed in the config file if it
turns into a problem.

However, this seems a little more convoluted than what I've seen posted
elsewhere. That's why I'm wondering if I've done something wrong.
Thanks - John
-- 
John A. Sullivan III
Open Source Development Corporation
+1 207-985-7880
jsullivan@opensourcedevel.com

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