I need to increase screen resolution to 1024x800 for all my XEN console.

I tried to place


at the end of kernel line the file /boot/grub/grub.conf but it seems that most of the boots arguments are ignored during startup. Probably inside XenSever /boot it's not really used in order to launch CentOS.

I even tried to add boot option in the boot option tab (VM -> Property -> Boot Option) but doesn't work.

Pls help. Thanks Max


have you tried adding extra="vga=791" in your domU-vmname.cfg file? That will set permanent kernel parameters for domain. For single kernel argument passing use xm create domU-vmname.cfg extra="vga-791"

  • Which is the path of this file in the XEN server? – Max Cuttins Mar 4 '14 at 18:05

The Xen virtual frame buffer may be limited to an 800x600 resolution.

On my Solaris 11 Express (Domain0) machine, I initially setup a VNCSever on CentOS (DomainU) and connect it via VNCViewer in Domain0.

But later I found a superior solution that is X11Forwarding provided by sshd in CentOS. In this way I can detach any virtual display device in DomianU configuration and in Domain0 use ssh with -X option to connect being able to run graphic applications like Firefox relying on Domain0 X11 which means 3D and hardware acceleration! If the CentOS is at the same time paravirtualized then you have near native DomainU performance in every aspect either CPU, RAM, Disk, Network or even Graphics!

Great thanks to the X11 client–server model where the communication protocol between server and client operates network-transparently! This is even advanced today. What a great feat it is back in 1984 when X11 takes its inception! And this is the reason why I prefer X11 to Wayland.

Presently, I'm considering XDMCP which has better performance without the encryption overhead induced by SSH.


Beyound the SSH X11Forwading way I succeded in XDMCP!

Use Xnest or Xephyr in Domain0:

Xnest :1 -geometry 1280x800 -query 10.0.1.x

Xephyr :1 -screen 1280x1024 -query 192.168.1.x

The only thing you have to do is to enable remote login in your VM or DomainU by manually editing /etc/gdm/custom.cfg or using the gdmsetup GUI program. Here CentOS 5 DomainU is taken as an example. In Ubuntu things will be a little differrent.

This approach is very different to VNC which is like Microsoft's RDP (screen capture) while XDMCP utilizes your Domain0's graphic power to assist DomainU system. That is comparable to Xen VGA passthrough in terms of performance.

Remember X11 was specifically designed to be used over network connections rather than on an integral or attached display device. X features network transparency: the machine where an application (the client application, for instance Firefox in your VM or DomainU) runs can differ from the user's local machine (the display server, that is the X11 in your Domain0). This approach allows both 2D and 3D operations to be fully accelerated on the user's local X server.

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