Enable frame buffer in grub2

With legacy grub, if you want to enable frame buffer built in kernel, the option "vga=xxx" is needed in boot command.
However, grub2 provides a newer way to enable the feature. You should set gfxpayload=1280x1024x32, and insmod vbe manually if needed. So where to add? I write it to /etc/grub.d/40_custom, as it is an user custom hook script.

cat <<EOF
insmod vbe
set gfxpayload=1280x1024x32
EOF

You can use vbeinfo in grub2 shell to look up which modes are available.
By the way, DO NOT FORGET to run:

# update-grub

to make newer grub.cfg generated.