If you would like to configure the Raspberry Pi to use DHCP, ''leave the "headless" file empty'', and the Raspberry Pi should be assigned an IP Address dynamically.

If "RESIZE" is in the "headless" file, the root filesystem will be expanded to the maximum size of the sd card via the service rootfs-resize. If "SWAP"(requires the value in megabytes) exists in the "headless" file, a swap file will be created of the specified size, and then activated.