Fixing MAC Address from Userspace
If you find that your 4Kopen board's MAC address changes on each boot, then it may be necessary to re-program it.
A symptom of this is that the board's IP is different each time it boots too.
You should be able to locate your MAC address on a sticker on your board - it should be six groups of two hexadecimal digits (0-9, A-F).
On the 4Kopen board, the MAC address is stored in the SPI flash, which can be updated using the following command:
printf "ethaddr=11:22:33:44:55:66\0" | sudo dd of=/dev/mtdblock0 seek=851968 oflag=seek_bytes
printf "\0" is necessary to ensure that the data is terminated correctly
$ dd if=/dev/mtd0 skip=851968 count=26 iflag=skip_bytes,count_bytes status=none | hexdump -Cv
00000000 65 74 68 61 64 64 72 3d 30 30 3a 30 30 3a 30 30 |ethaddr=00:00:00|
00000010 3a 30 30 3a 30 30 3a 30 30 00 |:00:00:00.|