SYSTEMD-ID128(1) systemd-id128 SYSTEMD-ID128(1)
NAME
systemd-id128 - Generate and print sd-128 identifiers
SYNOPSIS
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...]
DESCRIPTION
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.
OPTIONS
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[1] for
more discussion.
Added in version 244.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
EXIT STATUS
On success 0 is returned, and a non-zero failure code otherwise.
EXAMPLES
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.
SEE ALSO
systemd(1), sd-id128(3), sd_id128_get_machine(3)
NOTES
1. Universally Unique Identifiers
https://en.wikipedia.org/wiki/Universally_unique_identifier#Format
systemd 255 SYSTEMD-ID128(1)
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