[Libvir] Re: [Xen-users] SOLVED Re: cannot use vncviewer and VMM graphics console to access HVM guest on RHES 5

Daniel P. Berrange berrange at redhat.com
Fri Jun 1 18:18:50 UTC 2007

On Fri, Jun 01, 2007 at 02:13:15PM -0400, Glen Deem wrote:
> Hi Dan,
> I'm with you about the VNC authentication.
> But I still don't understand the logic behind assigning HVM displays.
> Instead of clear "domU ID is the display number" (vncunused 0), the
> Virtual Machine Manager assigns vncunused to 1 and then calculates the
> 5900+ port, I suppose depending on what port is not occupied (BTW
> where exactly is this code in the source, please?).

Virt-manager doesn't calculate the port numbers - QEMU / Xen does
that - it starts at 5900 and tries to bind() to it, adding 1 and
retrying until it works. 'DomU ID is the display number' doesn't
scale - if your host has been up for a while / run alot of guests
your domU ID get up into the 1000's, 10,000's or more, and you
will easily clash port numbers with other apps on the machine.

> Why is that? And how am I suppose to find out what that port number is
> if I'd want to connect to a VMM-created vm manually with my vnc
> client?

In current RHEL-5

  virsh dumpxml  <dom name> | grep graphics

Or in Fedora you can now ask

 virsh vncdisplay <doma name>

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