Xen users - Mar 2007 - Remote access to domU console using vnc

I have an FC6 dom0 running on a headless server.  I want to install a
CentOS 4.4 domU with a console accessed using vnc from a remote machine.
I *think* I should be able to do this from my understanding of the
documentation.

I''ve configured a domU to boot from an ISO image to do the CentOS
install and run xm create.  netstat on dom0 shows there''s a listener
on 0.0.0.0:5900, but I am unable to connect using vnc from my remote
system.  vncviewer reports "connection refused".  dom0 is not running
any firewalling and the relevant parts of the domU config file are:

  vnc = 1
  vnclisten=''0.0.0.0''
  vncconsole = 0

Any ideas what I need to do to make it work?

James

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James Fidell wrote:
<snip />
> I''ve configured a domU to boot from an ISO image to do the CentOS
> install and run xm create.  netstat on dom0 shows there''s a
listener
> on 0.0.0.0:5900, but I am unable to connect using vnc from my remote
> system.  vncviewer reports "connection refused".  dom0 is not
running
> any firewalling and the relevant parts of the domU config file are:
> 
>   vnc = 1
>   vnclisten=''0.0.0.0''
>   vncconsole = 0
> 
> Any ideas what I need to do to make it work?
>
Hi James,

I ran into this before.  In order to be able to attach to the :0 desktop 
you must specifically allow it.

   Desktop --> Preferences --> Remote Desktop

hth,
:m)

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Mike Wright wrote:
> James Fidell wrote:
> <snip />
>> I''ve configured a domU to boot from an ISO image to do the
CentOS
>> install and run xm create.  netstat on dom0 shows there''s a
listener
>> on 0.0.0.0:5900, but I am unable to connect using vnc from my remote
>> system.  vncviewer reports "connection refused".  dom0 is not
running
>> any firewalling and the relevant parts of the domU config file are:
>>
>>   vnc = 1
>>   vnclisten=''0.0.0.0''
>>   vncconsole = 0
>>
>> Any ideas what I need to do to make it work?
>>
> Hi James,
> 
> I ran into this before.  In order to be able to attach to the :0 desktop
> you must specifically allow it.
> 
>   Desktop --> Preferences --> Remote Desktop
Hmmm.  Where do I actually do this?  All I have on dom0 is an ssh
session -- it''s completely headless; there''s no GUI at all. 
And the
domU isn''t even installed yet.

James

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> Hmmm.  Where do I actually do this?  All I have on dom0 is an ssh
> session -- it''s completely headless; there''s no GUI at
all.  And the
> domU isn''t even installed yet.
I think you want to do the qemu install technique instead.

Do you have the image file or partitition already ready?

Here''s the partition based technique:

% qemu -hda <path-to-image-file> -cdrom /path/to/myiso.iso -boot d -vnc
<localhostip>:2





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Kraska, Joe A (US SSA) wrote:
>> Hmmm.  Where do I actually do this?  All I have on dom0 is an ssh
>> session -- it''s completely headless; there''s no GUI
at all.  And the
>> domU isn''t even installed yet.
> 
> I think you want to do the qemu install technique instead.
> 
> Do you have the image file or partitition already ready?
> 
> Here''s the partition based technique:
> 
> % qemu -hda <path-to-image-file> -cdrom /path/to/myiso.iso -boot d
-vnc
> <localhostip>:2
It seems there is an alternative solution, at least for getting me
through the installation.  I have set up an ssh tunnel from my
desktop machine (where I am running the vncviewer) forwarding port
5900 to localhost:5900 on dom0 on the remote server.  Connecting
vncviewer to localhost:5900 now gives me a console on my domU :)

Once I have the domU installed, is there no way to configure xen to
allow remote vnc sessions to the domU console directly (the domU
won''t be running X on it''s virtual console, so I
don''t think running
a vnc server inside domU is an option).

James

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> Once I have the domU installed, is there no way to configure xen to
> allow remote vnc sessions to the domU console directly (the domU
> won''t be running X on it''s virtual console, so I
don''t think running
> a vnc server inside domU is an option).
The above confused me, I''ll say!

So, if you''re not running X, what''s the use of a vnc session
anyway?

Just ssh directly to the domU.

Or attach to its serial console with "xm console <domid>"

If I''m confused, and the domU is running X, just set up vncserver
as normal. Works fine.

I understand that there''s a difference between the management interface
and the fully functional interface. Are you drawing a distinction here?
If so, to what purpose?

Joe.



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Kraska, Joe A (US SSA) wrote:
>> Once I have the domU installed, is there no way to configure xen to
>> allow remote vnc sessions to the domU console directly (the domU
>> won''t be running X on it''s virtual console, so I
don''t think running
>> a vnc server inside domU is an option).
> 
> The above confused me, I''ll say!
Sorry.  Perhaps I didn''t explain myself very well.
> So, if you''re not running X, what''s the use of a vnc
session anyway?
The machine running Xen is not running X in dom0, nor in domU.  I am
running vncviewer on my desktop machine and wanted to connect to domU
to install an OS using that connection.
> Just ssh directly to the domU.
Not before I''ve installed an OS, though.  That''s what I was
trying to
do before my ssh forwarding trick that I posted about earlier today.
> Or attach to its serial console with "xm console <domid>"
I tried that, but nothing happened.  I''ve read that it doesn''t
work
with fully virtualized installations, but if that isn''t true then
presumably I have something wrong with my config.  I just don''t know
what :(

Unfortunately I don''t have another machine capable of running fully-
virtual VMs, so I can''t try it out locally.

Now the domU is installed and running, I *can* connect remotely from
my desktop box to <dom0>:5900 and get the domU console, so the reason
I couldn''t connect after I''d created domU looks like something
to
do with the installation process, but I''m guessing.  I''m
tempted to go
back and do another install whilst attempting to connect from my vnc on
my desktop just because I''m not sure I believe what was happening.

James

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> Now the domU is installed and running, I *can* connect remotely from
> my desktop box to <dom0>:5900 and get the domU console, so the reason
> I couldn''t connect after I''d created domU looks like
something to
> do with the installation process, but I''m guessing.  I''m
tempted to go
> back and do another install whilst attempting to connect from my vnc
on
> my desktop just because I''m not sure I believe what was happening.
I see what you''re saying. I believe that if you compiled up your
own qemu, you''d get what you want: a vnc port on the IP of your
local xen0 box. The qemu installation technique works reliably
for me. Although I run a text mode install in that vnc session.

Joe.



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James Fidell wrote:
> dom0 is not running
> any firewalling and the relevant parts of the domU config file are:
> 
>   vnc = 1
>   vnclisten=''0.0.0.0''
>   vncconsole = 0
> 
> Any ideas what I need to do to make it work?
Ran into the same issue with xen 3.0.4 on a Centos 4.4 dom0.
make sure your /etc/xen/xend-config.sxp contains
(vnc-listen ''XXX.XXX.XXX.XXX'')
(vnclisten ''XXX.XXX.XXX.XXX'')
and substitute XXX.XXX.XXX.XXX with the address of your dom0 NIC.

Did the trick for me.

/Håkan

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