On Fri, 2009-05-01 at 18:50 -0400, John A. Sullivan III wrote:
> On Sat, 2009-05-02 at 00:40 +0200, Herbert Poetzl wrote:
> > On Fri, May 01, 2009 at 06:05:15PM -0400, John A. Sullivan III wrote:
> > > On Fri, 2009-05-01 at 23:34 +0200, Herbert Poetzl wrote:
> > > > 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 ...
> >
> > > Sorry to be showing my ignorance again but what is "single IP special
> > > casing" that I should be disabling? Thanks - John
> >
> > A Linux-VServer context flag, which controls the
> > behaviour in case a single IP is assigned to a guest
> > (which can be optimized by replacing 0.0.0.0 with
> > that single IP, instead of keeping a list to check
> > against) ...
> >
> > http://linux-vserver.org/Capabilities_and_Flags
> >
> > (see nflags, SINGLE_IP)
> >
> > note, that in the kernel config, you can also set the
> > default behaviour (VSERVER_AUTO_SINGLE) which, when
> > enabled does set that flag automatically
> >
> > HTC,
> > Herbert
> <snip>
> Hmm . . . so then it sounds like one could ideally turn off both
> automatic settings in the kernel and use the flags to have the greatest
> flexibility to choose which treatment is best for each application. Am
> I finally starting to get it? - John
Ah, so I see the flags can be used to not only enable when the kernel is
not but disable when the kernel is. Thus it really doesn't matter; we
always have the flexibility. Thanks for pointing me in the right
direction - John
-- John A. Sullivan III Open Source Development Corporation +1 207-985-7880 jsullivan@opensourcedevel.com http://www.spiritualoutreach.com Making Christianity intelligible to secular societyReceived on Sat May 2 00:16:43 2009