Need to start up VM in 640x480 FB

[mveg]

In order to port a embedded project from an ARM target to Linux/x86, I have to create a Debian VM which starts in framebuffer mode with 640x480 resolution.

I used the command to make the VM start on framebuffer, but it seems it cannot go below 800x600 resolution.
All tutorials and guide I can find are related to starting the guest VM at high resolution modes, while I cannot find anything tackling with my issue.

I followed the suggestions found here, at thread 8319 (cannot post links as a new user):

# edit /etc/default/grub
Uncomment: #GRUB_GFXMODE=640x480
Modify it to required resolution: GRUB_GFXMODE=1024x768
Add the following: GRUB_GFXPAYLOAD_LINUX=keep
Save, exit, and run update-grub
Edit "/etc/modprobe.d/fbdev-blacklist.conf" and add vboxvideo
Reboot

using GRUB_GFXMODE=640x480 and creating the /etc/modprobe.d/fbdev-blacklist.conf file, but with no results - it keeps starting at 800x600

Can anyone help on this? I am currently using Debian 9, can move to another version in case of incompatibilities.

[scottgus1]

Someone knowing how to do this may come along, (I don't) but I can give you a hint where to look.

Virtualbox is just a "hardware" provider, like Gigabyte or MSI or Biostar. What you install in Virtualbox has its own commands on how to set resolution, etc. Pretend that you are on a real PC and Virtualbox is not involved, then try to set things directly in the guest OS. Look in the Debian help files and forums to see how to force 640x480.

There is in the guest window a View menu, with a Virtual Screen # popout, and a set of Resize To choices, one of which is 640x480, but I don't know if that will help.

[mveg]

Thanks for your feedback. If I try to force a 640x480 resolution from View -> Virtual Screen 1 -> Resize menu, it is just ignored. I was thinking that, since Virtualbox acts as the HW provider, it could force the HW specifics - namely, the screen size.

[scottgus1]

If I try to force a 640x480 resolution from View -> Virtual Screen 1 -> Resize menu, it is just ignored.

I have just discovered that the Guest Additions need to be up and running inside the guest for the Resize choices to work. Are your Resize choices grayed out? On an XP guest I tested, the Resize coices are grayed out until I log in and the Guest Additions icon appears in the system tray. The Resize choices are not active in the Login screen.

[fth0]

I was thinking that, since Virtualbox acts as the HW provider, it could force the HW specifics - namely, the screen size.

I don't know if it will work in your case, but you could try the following commands (replace the VM name):

Code: Select all

VBoxManage setextradata "VM name" VBoxInternal/Devices/vga/0/Config/MaxBiosXRes 640
VBoxManage setextradata "VM name" VBoxInternal/Devices/vga/0/Config/MaxBiosYRes 480