systemd Developer Lennart Poettering lennart@poettering.net machine-id 5 machine-id local machine ID configuration file /etc/machine-id The /etc/machine-id file configures the unique machine id of the local system that is set during installation. It should contain a single newline-terminated, hexadecimal, lowercase 16 character machine ID string. The machine ID is usually generated from a random source during system installation and stays constant for all subsequent boots. Optionally, for stateless systems it is generated during runtime at boot. The machine ID does not change based on user configuration, or when hardware is replaced. This machine id follows the same format and logic as the D-Bus machine ID. Programs may use this ID to identify the host with a globally unique ID in the network, that does not change even if the local network configuration changes. Due to this and its greater length it is a more useful replacement than the gethostid3 call POSIX specifies. The simple configuration file format of /etc/machine-id originates in the /var/lib/dbus/machine-id file introduced by D-Bus. In fact this latter file might be a symlink to the /etc/machine-id. systemd1, gethostid3, hostname5