| # Chrome OS Flex ID |
| 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`. |
| |
| ## CloudReady Legacy Client 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-`. |
| |
| ## DMI Serial Number |
| 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. |
| |
| ## MAC Address |
| 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`. |
| |
| ## Kernel UUID |
| If all of the above fails, a random UUID generated from |
| `/proc/sys/kernel/random/uuid` will be used. |
