virt-install ignoring vnc port/listen?

Question

I'm trying to create kvm machine on remote host.

The host is running debian testing.

Did use this command:

virt-install --name debian-test \
    --os-type=linux \
    --os-variant=debianwheezy \
    --cdrom /media/media/software/iso/debian-testing-amd64-netinst-2014-01-16.iso \
    --graphics vnc,listen=0.0.0.0,port=20001 \
    --disk pool=default,format=raw,size=20 \
    --ram 2048 \
    --vcpus=2 \
    --network bridge=virbr0 \
    --hvm \
    --virt-type=kvm

But when it is created, it listens on:

=# virsh domdisplay debian-test
vnc://localhost:14101

When I had port=40001 in creation, it was listening on port 34101, so it looks like the port is treated as some kind of offset?! In any way - listen is not being used at all, and being able to connect from localhost is not what I want right now.

What am I doing wrong?

Solution

You aren't doing anything wrong. The VNC protocol specifies that the "port" isn't actually a port, but an offset from 5900, the default VNC port.

Thus localhost:0 would connect to port 5900, localhost:1 would connect to port 5901, etc.

---

By default, libvirt only binds VNC listeners to localhost, regardless of what you specify on the command line. To change this, you need to edit the appropriate option in /etc/libvirt/qemu.conf.

# VNC is configured to listen on 127.0.0.1 by default.
# To make it listen on all public interfaces, uncomment
# this next option.
#
# NB, strong recommendation to enable TLS + x509 certificate
# verification when allowing public access
#
#vnc_listen = "0.0.0.0"

Make sure to reload or restart libvirtd after making this change.

Comments

[sciurus]

Interesting that 20001-14101=5900, the default VNC port.