Index · Directives systemd 232

Name

sd_id128_get_machine, sd_id128_get_boot, sd_id128_get_invocation — Retrieve 128-bit IDs

Synopsis

#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);
 

Description

sd_id128_get_machine() returns the machine ID of the executing host. This reads and parses the machine-id(5) 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 random(4) 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.exec(5) 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-id(5).

For more information about the "sd_id128_t" type see sd-id128(3).

Return Value

The two calls return 0 on success (in which case ret is filled in), or a negative errno-style error code.

Notes

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 "libsystemdpkg-config(1) file.

See Also

systemd(1), sd-id128(3), machine-id(5), systemd.exec(5), sd_id128_randomize(3), random(4)