grub-install --target x86_64-efi --removable /dev/sda

set timeout=3
menuentry 'Ubuntu' {
    chainloader /efi/ubuntu/grubx64.efi
}
menuentry 'Ubuntu Studio' {
    chainloader /efi/ubuntustudio/grubx64.efi
}
menuentry 'Windows' {
    chainloader /efi/Microsoft/Boot/bootmgfw.efi
}
menuentry 'Firmware Setup' {
    fwsetup
}