We can have another option, as follows,to boot the system from the hard disk after we install the system using the previous configuration:

label 2. x86vbox (ROOT=/dev/sda1, serial port) 
menu x86vbox_sda1_S3 
kernel x86vbox/kernel 
append ip=dhcp console=ttyS3,115200 initrd=x86vbox/initrd.img androidboot.hardware=x86vbox DEBUG=2 SRC=/android-x86vbox ROOT=/dev/sda1 

In the preceding configuration, we use the /dev/sda1 device as the root and we don't have the INSTALL=1 option. With this configuration, the virtual machine will boot to the Android system from the hard disk /dev/sda1 and the debug output will print to the virtual serial port.

We can use another similar configuration that prints the debug output to the screen.