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$ cat /proc/device-tree/serial-number 0000000061679646 $ cat /proc/device-tree/serial-number 00000000550945e3
This problem became apparent because a running application on the device (Raspbian stretch), which uses the wlan0 MAC address, was returning an unexpected value. For reference, the eth0 MAC is equal to the last 24 bits of the serial number, and the wlan0 MAC is equal to that hex value XOR 0x555555. The MAC addresses are being generated from the serial number(s) correctly, but on each call the underlying serial is "randomized" so the reported MAC changes.
I am about 98% sure that what happened here is the SD card was removed from one running device, and put into another, new device. The OS has apparently cached the old serial number somewhere, and which of those values is returned seems nondeterministic.
Have any of you dealt with a similar problem before? I'm hoping I can wipe delete a file somewhere and be good to go. Thanks in advance!