Change VNC listen address in Libvirt without restarting VM

Question

Is there a way to to edit the listen address of a Libvirt-Machine on the fly? At the moment it seems like when I want to edit the listen address, I have to shut down the corresponding VM first, then edit the xml and redefine the domain.

I'm currently building a small web application (libvirt frontend) where I would like to implement a function called "enable / disable vnc" - however, that doesn't seem possible to me at the moment if the only way is shutting down the vm.

Solution 1

You have to go to QEMU Monitor and run:

change vnc display,options

Where display is <host>:<display_number> or unix:<path> or none. Options are options for display. See: https://qemu.weilnetz.de/doc/qemu-doc.html#sec_005finvocation

E.g. To change the port to 5905 and accept VNC connections for any host:

change vnc :5

If you are using virsh, use "qemu-monitor-command":

virsh # qemu-monitor-command <domain> --hmp change  vnc :5

Solution 2

No, it doesn't seem possible to change the VNC display dynamically. I don't think that KVM supports it anyway, so libvirt can't provide it.

What you could do is put something in front of the VNC port as a proxy, like socat. You'd setup the VM on a localhost address which can't be accessed from outside, and then to enable it start a proxy on the external IP.

Comments

[lzap]

Right QEMU does not support this: code.metager.de/source/xref/libvirt/src/qemu/… (except password)

[Antoine Rodriguez]

you saved me about : how to disable vnc display. For those who search here is the command : qemu-monitor-command <domain> --hmp change vnc none