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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLES | SEE ALSO | NOTES | COLOPHON |
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SYSTEMD-ID128(1) systemd-id128 SYSTEMD-ID128(1)
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...] var-partition-uuid
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=app-id 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.
var-partition-uuid prints a UUID which, following the Discoverable
Partitions Specification[1], should be used as the GPT partition
UUID for /var/, being derived from the GPT partition type, keyed
by the local /etc/machine-id. Added in version 257.
The following options are understood:
-p, --pretty
Generate output as programming language snippets.
Added in version 240.
-P, --value
Only print the value. May be combined with -u/--uuid.
Added in version 255.
-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.
Added in version 240.
-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[2] for more discussion.
Added in version 244.
--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
Print a short help text and exit.
--version
Print a short version string and exit.
On success 0 is returned, and a non-zero failure code otherwise.
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.
systemd(1), sd-id128(3), sd_id128_get_machine(3)
1. Discoverable Partitions Specification
https://uapi-group.org/specifications/specs/discoverable_partitions_specification
2. Universally Unique Identifiers
https://en.wikipedia.org/wiki/Universally_unique_identifier#Format
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
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 258~rc2 SYSTEMD-ID128(1)
Pages that refer to this page: sd-id128(3), sd_id128_get_machine(3), sd_id128_randomize(3), systemd.directives(7), systemd.index(7), systemd-gpt-auto-generator(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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