armbian-install: can we set a custom or random macaddress ?

[Dantes]

 

I had a need to change the macaddress of this device, after looking through the bootloader I spotted 2 offsets:

• 0x380400 macaddress NIC1
• 0x380406 macaddress NIC2

 

I would love an option in the installer, but I did it manually now:

 

# dd if=/dev/mmcblk2 bs=16M count=1 of=bootloader
1+0 records in
1+0 records out
16777216 bytes (17 MB, 16 MiB) copied, 0,0736928 s, 228 MB/s

# read_mac bootloader 0x380400
9c:d5:dc:b2:ce:1c

# write_mac bootloader 0x380400 $(random_mac)
write_mac bootloader 0x380400 $(random_mac)

# read_mac bootloader 0x380400
b0:3f:1a:83:9a:da

 

After scripting a couple of functions of course:

 

### Functions read_mac , write_mac and random_mac are hereby licensed under GPLv3

# read_mac file offset
# read_mac bootloader 0x380400
# read_mac /dev/mmcblk2 0x380400
read_mac(){ 
  dd if=$1 bs=1 count=6 skip=$(($2)) 2>/dev/null |\
    xxd -l 16 -p | sed 's/../:&/g;s/^://'
}

# write_mac file offset macaddress
# write_mac bootloader 0x380400 aa:bb:cc:dd:ee:ff
# write_mac /dev/mmcblk2 0x380400 aa:bb:cc:dd:ee:ff
write_mac(){
  for hex in $(echo $3|tr ':' ' ');do printf "\x$hex";done |\
    dd of=$file bs=1 count=6 seek=$(($offset)) conv=notrunc 2>/dev/null
}

# print a random macaddress
random_mac(){
  printf "%012x" \
    $(( 0x$(hexdump -n6 -ve '/1 "%02X"' /dev/urandom) & 0xFCFFFFFFFFFF )) |\
      sed 's/../:&/g;s/^://'
}

 

Edited June 4, 2023 by Dantes