[CentOS-virt] hot-plug vfb on Xen domU?

Chris Wik

chris at anu.net
Sun Jan 16 00:22:30 UTC 2011

On 16.01.2011, at 00:12, Pasi Kärkkäinen wrote:

>> * Related, I can't figure out how I can change the VNC password without restarting the domU, as the password is specified in the vfb config.
>> Is what I am trying to do possible? How?
> I wonder if the password is stored inside the qemu-dm process (vnc server),
> or in xenstore.. 
> If it's in xenstore then it's easy to change it.

Thanks for the tip, I never looked into xenstore before.

So I found that the vncpass is stored in xenstore:

# xenstore-read /local/domain/0/backend/vfb/<domain id>/0/vncpasswd
-> test123

# xenstore-write /local/domain/0/backend/vfb/19/0/vncpasswd test234

# xenstore-read /local/domain/0/backend/vfb/<domain id>/0/vncpasswd
-> test234

OK, so I can read and write the password. However, when I open a VNC connection, the new password is not in effect, instead the old one is still valid.

I noticed the qemu-dm process which looks like it might be responsible for setting up the vnc server:

# ps ax | grep vnc
12301 pts/0    Sl     0:00 /usr/lib64/xen/bin/qemu-dm -M xenpv -d <domain id> -domain-name <domain name> -vnc<vnc port>,password -k en-us

I tried sending this pid a HUP signal to see if it would reload the password, but instead it just died. Do you think I'm on the right track here? Any further suggestions would be very much appreciated.


Chris Wik
Anu Internet Services Ltd

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