virtualbox.org

I have installed Debian 9 in Windows Host without GUI. Since console size was small i successfully changed resolution to 1024x768 via GRUB_GFXMODE and GRUB_GFXPAYLOAD in /etc/default/grub. However, if i install Virtual Box Guest Additions, it does not work anymore. As soon as i selected boot option from GRUB menu it starts to boot and during the boot process it changes resolution to some smaller resolution. If i uninstall guest additions it keeps the resolution from GRUB menu.

Any ideas?

Without Xorg the auto-resize and/or increased screen resolution provided with the guest additions will not change. You must change console mode using framebuffers.

One other thing. The Guest Additions may interfere with the GFX_MODE because it requires X and to work around that you need to black list vboxvideo.

Blacklisting vboxvideo did the trick. Thank you for your help.

For the uninitiated of us, would blacklisting mean something like this?
https://wiki.debian.org/KernelModuleBlacklisting

Exactly!