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. This ID may be used wherever a unique identifier for the
local system is needed. However, it is recommended to use this ID
as-is only in trusted environments. In untrusted environments it is
recommended to derive an application specific ID from this machine
ID, in an irreversable (cryptographically secure) way. To make this
easy sd_id128_get_machine_app_specific() is provided, see below.
sd_id128_get_machine_app_specific() is similar to
sd_id128_get_machine(), but retrieves a machine ID that is specific
to the application that is identified by the indicated application
ID. It is recommended to use this function instead of
sd_id128_get_machine() when passing an ID to untrusted environments,
in order to make sure that the original machine ID may not be
determined externally. The application-specific ID should be
generated via a tool like journalctl --new-id128, and may be compiled
into the application. This function will return the same
application-specific ID for each combination of machine ID and
application ID. Internally, this function calculates HMAC-SHA256 of
the application ID, keyed by the machine ID.
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_machine_app_specific(), 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,
For more information about the "sd_id128_t" type see sd-id128(3).
sd_id128_get_invocation() interfaces are available as a shared
library, which can be compiled and linked to with the
"libsystemd" pkg-config(1) file.
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
page was obtained from the project's upstream Git repository
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systemd 233 SD_ID128_GET_MACHINE(3)