it isn't bound automatically so you need
	bind -b '#v' /dev
to make it appear in /dev, or use
	echo -n 'size 800x600x8' >'#v/vgactl'

that's probably still not what you intend, because VGA being what it is,
a host of major and minor register values need to be adjusted in most cases,
in a device-dependent way.  use aux/vga, described by vga(8).
read the manual page first, though.  aux/vga eventually sets the
using vgactl, but sets all those registers first, if it can.
it needs to be done outside rio.