Higher Screen Resolution without VirtualBox Guest Additions

From Kicksecure

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Introduction[edit]

Info This procedure is experimental and has not been widely tested.

This procedure is an alternative to using VirtualBox Guest Additions for a higher screen resolution. See also: Security Considerations.

Before attempting this procedure it is recommended to have a recent backup in case problems are encountered. However, it should be possible to undo these changes.

Higher Screen Resolution without VirtualBox Guest Additions[edit]

To achieve a higher screen resolution without installing VirtualBox guest additions, complete the following steps.

1. Create a relevant configuration file.

For example, create a file called /etc/X11/xorg.conf.d/00-virtualbox-monitor.conf.

Create the directory if it does not already exist.

sudo mkdir -p /etc/X11/xorg.conf.d

2. Open the configuration file in an editor with root rights.

sudoedit /etc/X11/xorg.conf.d/00-virtualbox-monitor.conf

3. Add the following contents.

Section "Device" Identifier "VirtualBox-Device" Option "Monitor-default" "VirtualBox-Monitor" EndSection Section "Monitor" Identifier "VirtualBox-Monitor" VendorName "VirtualBox" ModelName "VirtualBox" HorizSync 1.0 - 1000.0 VertRefresh 1.0 - 1000.0 Option "MinClock" "1.0" Option "MaxClock" "10000.0" Option "Primary" "True" Option "PreferredMode" "1600x1200" EndSection Section "Screen" Identifier "MyScreen" Device "VirtualBox-Device" Monitor "VirtualBox-Monitor" EndSection

4. Run restart the display manager reboot.

Kicksecure ™ will now be set to 1600x1200 mode by default.

5. Optional: Change the default resolution mode.

If a default resolution mode other than 1600x1200 is preferred, then change the "PreferredMode" option in the "Monitor" section.

It is possible to dynamically switch modes from the command line with "xrandr --output default --mode [resolution value]". To view a list of available modes, run "xrandr".

6. Optional: Change the screen resolution using the XFCE graphical user interface.

  • Start MenuSystem ToolsDisplay.

If the preferred screen resolution is not listed (e.g. 1440x900), try running this command on the host.

vboxmanage setextradata "VM Name" "CustomVideoMode1" "1440x900x32"

If the Start Menu button is not visible (because it is outside the screen), then start Konsole and manually start System Settings by running systemsettings.

Ubuntu[edit]

Info This procedure was recommended for an earlier version of Ubuntu (14.04). Functionality in later versions has not been confirmed (e.g. Ubuntu 20.04).

If Ubuntu has a screen resolution of 640x480, it may be possible to achieve 1024x768 by:

  1. Running xdiagnose.
  2. Changing any setting under Debug -- marking them all or unmarking "Enable automatic crash reporting" were previously reported to work.
  3. Reboot.

Troubleshooting[edit]

If this procedure does not work or you want to revert the changes, delete /etc/X11/xorg.conf.d/00-virtualbox-monitor.conf.

sudo rm /etc/X11/xorg.conf.d/00-virtualbox-monitor.conf

Next, restart the display manager or reboot.

Technical Information[edit]

EDID[edit]

An anonymous user stated:

The reason you can't just get higher resolutions using xrandr "--newmode" and "--addmode" without an xorg.conf file appears to be that VirtualBox is not providing EDID information to the default VESA driver. The driver therefore makes the conservative assumption that it can't drive the "monitor" with the high clock rates needed for larger display sizes. The above config file tells the driver that it can use an effectively infinite range of clock rates.

Also see: VirtualBox get-edid output.

How to use xserver-xorg-video-modesetting?[edit]

Questions directed to the maintainers of the xserver-xorg-video-modesetting package and the debian-user mailing list went unanswered.

Interested readers might find the following resources helpful:

Footnotes[edit]



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