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