virtualbox.org

I would like to know how to use full screen mode on rdesktop?

With RDP its a setting, I'm sure rdesktop has such a setting.

Read the documentation of Rdesktop, Ctrl+Alt+Enter puts rdesktop into fullscreen.

But when I use ctrl+alt+enter, the screen is not fully filled with the virtual machine screen.
I'm using Ubuntu as my host and guest system. When I go to the screen proporties, there is no option to change the screen resolution to a resolution greater than 800x600. How can I fix this problem?

That might be an rdesktop problem, not VB's. Do make sure that the resolution is set to 'default', and nothing else. That will let X decide which resolution is usable and will be used as such.

when I go to the Display properties, there is no default option to be selected. Any suggestions to enable the default option?

I think you may have to give the virtual machine more memory for the virtual video card. If the virtual machine is set at 800x600 then the RDP session will be that. You have to have the guest match the RDP session size you are looking to achieve. Example: My desktop is 1024x768 and my virtual machine is setup the same. Now when I login it looks seamless. I hope this helps in some way.

The default memory allocation (12 MB) is more than enough. Also, RDP doesn't take the resolution from the system it connects to, you either supply that through the command line, or it tries the highest available windowed mode of your own system. It's possible it defaults to 1024x768 even though you have a higher resolution monitor. Check that with the rdesktop documentation.