Add README

README.md

+## CS 2xx Course VM
+
+### Requirements
+
+For now, this script needs to be run on a 64-bit Arch Linux host, with
+`extra/arch-install-scripts` and `community/virtualbox` installed.
+
+If you don't need to create a VirtualBox VM and just want the raw disk image
+(runnable with, e.g., QEMU), you can comment out the bottom of the script. 
+
+If you do want the VirtualBox VM, it's better if VirtualBox is not running.
+
+
+### Building
+
+To build, edit the top of `create_vm.sh` and change `ARCH` to either `x86_64`
+or `x86`. Then run the script.