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.

       --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.

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