mjhjmtu

I have VirtualBox instance of Centos 5. The screen size is quite small (800*600) and I'd like to increase it to 1280*1080. Under the Gnome preferences for "Screen Resolution" I only get the option for 600*800 or 640*480.

I've tried editing my xorg.conf (based on this tutorial http://paulsiu.wordpress.com/2008/09/08/creating-and-managing-centos-virtual-machine-under-virtualbox/) but it doesn't seem to have made a difference. Here is a snippet from the edited section:

Section "Screen"
 Identifier "Screen0"
 Device "Card0"
 Monitor "Monitor0"
 DefaultDepth 24
 SubSection "Display"
 Viewport 0 0
 Depth 24
 Modes "1280x800"
 EndSubSection
EndSection

Does anyone know how to do this?

A maximum resolution of 800x600 suggests that your X server inside the virtual machine is using the SVGA driver. SVGA is the highest resolution for which there is standard support; beyond that, you need a driver.

VirtualBox emulates a graphics adapter that is specific to VirtualBox, it does not emulate a previously existing hardware component like most other subsystems. The guest additions include a driver for that adapter. Insert the guest additions CD from the VirtualBox device menu, then run the installation program. Log out, restart the X server (send Ctrl+Alt+Backspace from the VirtualBox menu), and you should have a screen resolution that matches your VirtualBox window. If you find that you still need manual tweaking of your xorg.conf, the manual has some pointers.

There's a limit to how high you can get, due to the amount of memory you've allocated to the graphics adapter in the VirtualBox configuration. 8MB will give you up to 1600x1200 in 32 colors. Going beyond that is mostly useful if you use 3D.

I had the same problems with different setup:

Host OS: Linux Mint 17 Cinnamon 64-bit
Guest OS: Centos 6.6
Virtualbox: Oracle VM VirtualBox Manager 4.3.10_Ubuntu

Solution which worked for me:

1. 
   

   Install Virtualbox --> Devices, Insert Guest Additions CD image

   
   
   

   [root@centos6 ~]# cd /media/VBOXADDITIONS_4.3.10_93012/
   ./VBoxLinuxAdditions.run
   

   
   


2. 
   

   get custom resolution string:

   
   
   

   [root@centos6 ~]$ cvt 1600 900
   # 1600x900 59.95 Hz (CVT 1.44M9) hsync: 55.99 kHz; pclk: 118.25 MHz Modeline "1600x900_60.00" 118.25 1600 1696 1856 2112 900 903 908 934 -hsync +vsync
   

   
   


3. 
   

   set custom resolution string:

   
   
   

   [root@centos6 ~]$ xrandr
   Screen 0: minimum 64 x 64, current 1024 x 768, maximum 16384 x 16384
   VBOX0 connected 1024x768+0+0 0mm x 0mm
    1024x768 60.0*+ 60.0*
    1600x1200 60.0 
    1440x1050 60.0 
    1280x960 60.0 
    800x600 60.0 
    640x480 60.0 
   
   [root@centos6 ~]$ xrandr --newmode "1600x900_60.00" 118.25 1600 1696 1856 2112 900 903 908 934 -hsync +vsync
   
   [root@centos6 ~]$ xrandr --addmode VBOX0 "1600x900_60.00"
   

   
   



4. use normal system administration config dialog to change resolution to 1600 x 900 which was not available before.

HTH,
Magnus

You need Virtual Box guest extensions.

In order to install them you first need the RPMForge repository added for yum, follow these instructions:

http://wiki.centos.org/AdditionalResources/Repositories/RPMForge#head-5aabf02717d5b6b12d47edbc5811404998926a1b

Then run this command in a terminal:

yum install dkms

In my case (virtualbox 5 + centos 7), all I did is install the "Guest additional cd image", then restart the vm, and make it full screen when start, it automatically take the biggest resolution.

I think u might forget to reboot or didn't full screen it via host + F.

My virtual machine suddenly no longer supported full-screen.

Eventually, the fix was easy: I had to update to the newest version of VirtualBox, then re-install the newest version of Guest Additions. After doing that then restarting my VM, the resolution was automatically the correct (full-screen) size.

on CentOS 7.5 on VirtualBox 5.2.22 the solution was:

1. install VirtualBox Additions


2. 
   

   create a kernel module configuration file for the module "vboxvideo". Without the "modeset" parameter the module fails to load.

   
   
   

   echo "options vboxvideo modeset=1" > /etc/modprobe.d/vboxvideo.conf

   
   


3. reboot