unwanted change to lower desktop resolution during tty1 virtual console boot process

[Patrick Schleizer <patrick-mailinglists@whonix.org>]

Not using any desktop environment. Not using any login manager. Using
Debian stretch inside VirtualBox.

Initially during boot the usual grub configuration [1] works for me. The
screen resolution get increased from to 1024x768.

However, as systemd continues booting, I see "Set console font and
keymap". Right before the virtual console (tty1) appears, the resolution
is reset to a lower 800x600. The window size decreased.

My questions:

1) What changes the tty screen resolution later in the boot process?
console-setup.service?

2) How to prevent the screen resolution from being changed or how to
change the screen resolution by the program that changes it
(console-setup.service?)?

fbset does not work at all inside VirtualBox. Error message:

ioctl FBIOPUT_VSCREENINFO: Invalid argument

Cheers,
Patrick

[1]
GRUB_GFXMODE=1024x768x24
GRUB_GFXPAYLOAD_LINUX=keep
or GRUB_GFXPAYLOAD_LINUX=1024x768x24