systemd Developer Lennart Poettering lennart@poettering.net sd_id128_get_machine 3 sd_id128_get_machine sd_id128_get_boot sd_id128_get_invocation Retrieve 128-bit IDs #include <systemd/sd-id128.h> int sd_id128_get_machine sd_id128_t *ret int sd_id128_get_boot sd_id128_t *ret int sd_id128_get_invocation sd_id128_t *ret sd_id128_get_machine() returns the machine ID of the executing host. This reads and parses the machine-id5 file. This function caches the machine ID internally to make retrieving the machine ID a cheap operation. sd_id128_get_boot() returns the boot ID of the executing kernel. This reads and parses the /proc/sys/kernel/random/boot_id file exposed by the kernel. It is randomly generated early at boot and is unique for every running kernel instance. See random4 for more information. This function also internally caches the returned ID to make this call a cheap operation. sd_id128_get_invocation() returns the invocation ID of the currently executed service. In its current implementation, this reads and parses the $INVOCATION_ID environment variable that the service manager sets when activating a service, see systemd.exec5 for details. The ID is cached internally. In future a different mechanism to determine the invocation ID may be added. Note that sd_id128_get_boot() and sd_id128_get_invocation() always return UUID v4 compatible IDs. sd_id128_get_machine() will also return a UUID v4-compatible ID on new installations but might not on older. It is possible to convert the machine ID into a UUID v4-compatible one. For more information, see machine-id5. For more information about the sd_id128_t type see sd-id1283. The two calls return 0 on success (in which case ret is filled in), or a negative errno-style error code. The sd_id128_get_machine(), sd_id128_get_boot() and sd_id128_get_invocation() interfaces are available as a shared library, which can be compiled and linked to with the libsystemd pkg-config1 file. systemd1, sd-id1283, machine-id5, systemd.exec5, sd_id128_randomize3, random4