How is android root filesystem created for android emulator?

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http://stackoverflow.com – I am currently working on Android ICS AOSP for android emulator. When I compile and create android images and load it using Android SDK (emualtor), I can see set of devices under /dev/ But when I see /out/target/product/generic/root/dev/ folder its empty. Now my question how this dev folder gets its devices during boot up time. Is there any configuration file in /system/ folder which helps in populating all the devices. Also, if I want to update or add more devices like /dev/block/sda1 so that I can mount another qemu raw image as sda1 or so? I can see emulator under -qemu as "-hda/-hdb file (HowTos)