systemd-id128 — Generate and print sd-128 identifiers
systemd-id128 [OPTIONS...] new
systemd-id128 [OPTIONS...] machine-id
systemd-id128 [OPTIONS...] boot-id
systemd-id128 [OPTIONS...] invocation-id
systemd-id128 [OPTIONS...] show [NAME|UUID...]
id128 may be used to conveniently print sd-id128(3) UUIDs. What identifier is printed depends on the specific verb.
With new, a new random identifier will be generated.
With machine-id, the identifier of the current machine will be printed. See machine-id(5).
With boot-id, the identifier of the current boot will be printed.
With invocation-id, the identifier of the current service invocation will be printed. This is available in systemd services. See systemd.exec(5).
With show, well-known IDs are printed (for now, only GPT partition type UUIDs),
along with brief identifier strings. When no arguments are specified, all known IDs are shown. When
arguments are specified, they may be the identifiers or ID values of one or more known IDs, which are
then printed with their name, or arbitrary IDs, which are then printed with a placeholder name. Combine
with --uuid to list the IDs in UUID style, i.e. the way GPT partition type UUIDs are
usually shown.
machine-id, boot-id, and show may be
combined with the --app-specific= switch to generate
application-specific IDs. See
sd_id128_get_machine(3)
for the discussion when this is useful. Support for show --app-specific= was added in
version 255.app-id
The following options are understood:
-p, --pretty¶Generate output as programming language snippets.
-P, --value¶Only print the value. May be combined with
-u/--uuid.
-a app-id, --app-specific=app-id¶With this option, identifiers will be printed that are the result of hashing the
application identifier app-id and another ID. The
app-id argument must be a valid sd-id128 string identifying the
application. When used with machine-id, the other ID will be the machine ID as
described in
machine-id(5), when
used with boot-id, the other ID will be the boot ID, and when used with
show, the other ID or IDs should be specified via the positional arguments.
-u, --uuid¶Generate output as a UUID formatted in the "canonical representation", with five groups of digits separated by hyphens. See the Wikipedia entry for Universally Unique Identifiers for more discussion.
--no-pager¶Do not pipe output into a pager.
--no-legend¶Do not print the legend, i.e. column headers and the footer with hints.
--json=MODE¶Shows output formatted as JSON. Expects one of "short" (for the
shortest possible output without any redundant whitespace or line breaks), "pretty"
(for a pretty version of the same, with indentation and line breaks) or "off" (to turn
off JSON output, the default).
-j¶Equivalent to --json=pretty if running on a terminal, and
--json=short otherwise.
-h, --help¶--version¶Example 1. Show a well-known UUID
$ systemd-id128 show --value user-home
773f91ef66d449b5bd83d683bf40ad16
$ systemd-id128 show --value --uuid user-home
773f91ef-66d4-49b5-bd83-d683bf40ad16
$ systemd-id128 show 773f91ef-66d4-49b5-bd83-d683bf40ad16
NAME ID
user-home 773f91ef66d449b5bd83d683bf40ad16
Example 2. Generate an application-specific UUID
$ systemd-id128 machine-id -u
3a9d668b-4db7-4939-8a4a-5e78a03bffb7
$ systemd-id128 new -u
1fb8f24b-02df-458d-9659-cc8ace68e28a
$ systemd-id128 machine-id -u -a 1fb8f24b-02df-458d-9659-cc8ace68e28a
47b82cb1-5339-43da-b2a6-1c350aef1bd1
$ systemd-id128 -Pu show 3a9d668b-4db7-4939-8a4a-5e78a03bffb7 \
-a 1fb8f24b-02df-458d-9659-cc8ace68e28a
47b82cb1-5339-43da-b2a6-1c350aef1bd1
On a given machine with the ID 3a9d668b-4db7-4939-8a4a-5e78a03bffb7, for the application 1fb8f24b-02df-458d-9659-cc8ace68e28a, we generate an application-specific machine ID (47b82cb1-5339-43da-b2a6-1c350aef1bd1). If we want to later recreate the same calculation on a different machine, we need to specify both IDs explicitly as parameters to show.