Change Screen Resolution For Ubuntu Running On VirtualBox

1) Devices->Install Guest Additions and your virtual Ubuntu should recognize a new CD. Open a terminal and run this command:

sudo /media/cdrom/VBoxLinuxAdditions.run

2) Open your guest machine’s xorg.conf file:

gksu gedit /etc/X11/xorg.conf

Find the device section, which should look like this:

Section "Device"
Identifier "Configured Video Device"
EndSection

Replace to :

Section "Device"
Identifier "Configured Video Device"
Driver "vboxvideo"
EndSection

3) Find the code like this :

Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
EndSection

replace with :

Section "Screen"
Identifier "Default Screen"
Device "VirtualBox graphics card"
Monitor "Generic Monitor"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1024x768"
EndSubSection
EndSection

4) Save the file, and restart your Virtual box.