cannot change screen size from 640x480 after 14.04 installation on VirtualBox OSX [duplicate]

After installing Ubuntu 14.04 guest on VirtualBox running on a Max OSX host, I am stuck with 640x480 screen resolution. Adding guest additions again doesn't help. Previous Ubuntu installations are fine with bigger resolution. The 'Detect Displays' button on the 'Display Settings' Settings screen is not reachable, because 640x480 is too small. I could not find a /etc/X11/xorg.conf file to configure manually.

Independently of your installed version of VirtualBox you should install the latest version of the VirtualBox Guest Additions into your Ubuntu-Guest. You can get it from the Ubuntu-Software-Repository.

Startup your guest and hit Ctrl+Alt+T to open a terminal session. Type

sudo apt-get install virtualbox-guest-dkms

to install the latest package. Restart the VM and enjoy screen-size.

Just had exaclty the same problem with Ubuntu 14.04 on Windows 7 VirtualBox. I've updated to latest version of Virtualbox (4.3.10 r93012) and it now works correctly. Make sure to install the latest version of Guest Additions (v4.3.10 at the moment).