I may expand this later. . . .
Query the file /proc/sys/kernel/random/uuid for a globally unique value. It produces a new value on each read. For a globally unique value that’s persistent between machine startup, query /proc/sys/kernel/random/boot_id.
[earth:/]120 % cat /proc/sys/kernel/random/uuid 78345a49-875f-48d3-aa80-130db5e57991 [earth:/]121 % cat /proc/sys/kernel/random/uuid d258123d-f2bd-49c0-89d6-e4db5d377776 [earth:/]122 % cat /proc/sys/kernel/random/boot_id e58a255a-0f6c-418f-ac0b-0fac81a5ff4a [earth:/]123 % cat /proc/sys/kernel/random/boot_id e58a255a-0f6c-418f-ac0b-0fac81a5ff4a