It was annoying to have only a resolution of 640×480 in the virtualbox instance of my new debian virtual instance. So I have had to do something. Here [1] I found the solution of the already well known problem:
In Grub2 the vga= parameter is deprecated.
To set a screen resolution for your console you can do the following log in as root
edit /etc/default/grub uncomment the GRUB_GFXMODE=640×480 and change the resolution to something you can use e.g. 1024×768
Add the line
GRUB_GFXPAYLOAD_LINUX=keep
to the file to have the same resolution at the Linux console. You do not edit the 00_header file as some suggest you need to do.run update-grub
run reboot to confirm that your changes worked!