DEADBEEF is actually an "old school programmer thing". But if we look into a stock debian image file . . .
$ sudo fdisk -lu cleanup/downloads/linux-images/bone-debian-7.8-console-armhf-2015-03-01-2gb.img
Disk cleanup/downloads/linux-images/bone-debian-7.8-console-armhf-2015-03-01-2gb.img: 1782 MB, 1782579200 bytes
184 heads, 31 sectors/track, 610 cylinders, total 3481600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
cleanup/downloads/linux-images/bone-debian-7.8-console-armhf-2015-03-01-2gb.img1 * 2048 3481599 1739776 83 Linux
$ sudo mount -o loop,offset=1048576 cleanup/downloads/linux-images/bone-debian-7.8-console-armhf-2015-03-01-2gb.img /media/rootfs
william@eee-pc:~$ cat /media/rootfs/etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto eth0
iface eth0 inet dhcp
# Example to keep MAC address between reboots
#hwaddress ether DE:AD:BE:EF:CA:FE
# The secondary network interface
#auto eth1
#iface eth1 inet dhcp
# WiFi Example
#auto wlan0
#iface wlan0 inet dhcp
# wpa-ssid "essid"
# wpa-psk "password"
# Ethernet/RNDIS gadget (g_ether)
# ... or on host side, usbnet and random hwaddr
# Note on some boards, usb0 is automaticly setup with an init script
iface usb0 inet static
address 192.168.7.2
netmask 255.255.255.0
network 192.168.7.0
gateway 192.168.7.1
As I recall there is also a script somewhere that did, or still sets this MAC address for the ethernet interface. Granted this is not what my own beaglebones are set to . . .