Function current_boot_id 

pub fn current_boot_id() -> Option<String>

Best-effort current boot identifier.

• Linux: /proc/sys/kernel/random/boot_id.
• macOS: a stable prefix of sysctl -n kern.boottime (the { sec = …, usec = … } half is stable across invocations on the same boot; the trailing human-readable date is not).
• Everything else: None.