Interesting info about temperatures and such can be found in places like: /sys/devices/virtual/thermal/thermal_zone0/temp or even /sys/devices/platform/axp81x_board/axp-regulator.41/regulator/regulator.2/microvolts. There is a shell-script in /usr/local/sbin for reading things, sudo /usr/local/sbin/pine64_health.sh. The sudo part is needed for the processor-info.
It turns out, the MAC address is set in the distro and not in the hardware. It will be set to some random address if none was specified, this being based on some property of the board such as a serial number. Some of the early versions used the same number for everyone, resulting in the same MAC address -- this has since been corrected. As of the recent (since 2018-10-27 dated kernels) the MAC address is taken from the last six octets in the file /etc/dhcpcd.duid, and remain fairly stable because this file is only written when missing.
In earlier kernels, which are no longer being developed, the MAC address being used, whether automatically generated or copied from the label on the board, is defined in the file /boot/uEnv.txt where there is a line something like
ethaddr=36:c9:e3:f1:b8:05
There are distinct MAC addresses printed on a label on the card, and thus, the line for ethaddr, the list of octets in /etc/dhcpcd.duid, could usefully be edited to refer to that instead, for example:
ethaddr=00:06:dc:8b:89:8c
or equivalently for /etc/dhcpcd.duid:
00:01:00:01:1f:ae:2d:86:00:06:dc:8b:89:8c
Similarly, the hostname can be changed from the default by editing it in /etc/hosts and in /etc/hostname
