This is a utility and library for generating a device-specific identifier known as a Flex ID. This was previously named Client ID, and is also a separate identifier from the client id used in UMA and crash reporting.
Flex ID can be used to account for the lack of VPD information by amd64 generic based platforms (such as the Reven board).
This utility will check a number of locations to attempt to find a useful source to define a non-random device identifier.
The Flex ID is stored at /var/lib/flex_id/flex_id.
The Flex ID is preserved through power wash and saved to mnt/stateful_partition/unencrypted/preserve/flex/flex_id.
This is a Client ID generated by CloudReady devices that is stored at mnt/stateful_partition/cloudready/client_id. It consists of the device's mac address and should be prepended with CloudReady-.
This is the serial number from DMI/SMBIOS information, read from /sys/devices/virtual/dmi/id/product_serial. Serial number is not guaranteed to be useful. There are certain criteria such as minimum length, and comparison with known bad strings that must be met to be useful.
This is the best case hardware MAC address that can be read from /sys/class/net/<device name>/address. Priority is given to eth0 and wlan0.
If all of the above fails, a random UUID generated from /proc/sys/kernel/random/uuid will be used.