/** The Linux kernel's per-boot identity at `/proc/sys/kernel/random/boot_id` —
 *  a fresh random UUID minted on every kernel boot, or null when unreadable
 *  (non-Linux dev, or the file is absent). Exact when present: a microVM
 *  recreate boots a new kernel (new id); a plain daemon restart within the same
 *  boot leaves it identical. */
export declare function readKernelBootId(): string | null;