ORG.FREEDESKTOP.HOSTNAME1(5)         ORG.FREEDESKTOP.HOSTNAME1(5)

     NAME
          org.freedesktop.hostname1 - The D-Bus interface of
          systemd-hostnamed

     INTRODUCTION
          systemd-hostnamed.service(8) is a system service that can be
          used to control the hostname and related machine metadata
          from user programs. This page describes the hostname
          semantics and the D-Bus interface.

     THE D-BUS API
          The service exposes the following interfaces on the bus:

              node /org/freedesktop/hostname1 {
                interface org.freedesktop.hostname1 {
                  methods:
                    SetHostname(in  s hostname,
                                in  b interactive);
                    SetStaticHostname(in  s hostname,
                                      in  b interactive);
                    SetPrettyHostname(in  s hostname,
                                      in  b interactive);
                    SetIconName(in  s icon,
                                in  b interactive);
                    SetChassis(in  s chassis,
                               in  b interactive);
                    SetDeployment(in  s deployment,
                                  in  b interactive);
                    SetLocation(in  s location,
                                in  b interactive);
                    GetProductUUID(in  b interactive,
                                   out ay uuid);
                  properties:
                    readonly s Hostname = '...';
                    readonly s StaticHostname = '...';
                    readonly s PrettyHostname = '...';
                    readonly s IconName = '...';
                    readonly s Chassis = '...';
                    readonly s Deployment = '...';
                    readonly s Location = '...';
                    @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                    readonly s KernelName = '...';
                    @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                    readonly s KernelRelease = '...';
                    @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                    readonly s KernelVersion = '...';
                    @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                    readonly s OperatingSystemPrettyName = '...';
                    @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                    readonly s OperatingSystemCPEName = '...';

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                    @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                    readonly s HomeURL = '...';
                };
                interface org.freedesktop.DBus.Peer { ... };
                interface org.freedesktop.DBus.Introspectable { ... };
                interface org.freedesktop.DBus.Properties { ... };
              };

          Whenever the hostname or other metadata is changed via the
          daemon, PropertyChanged signals are sent out to subscribed
          clients. Changing a hostname using this interface is
          authenticated via m[blue]polkitm[][1].

     SEMANTICS
          The static (configured) hostname is the one configured in
          /etc/hostname. It is chosen by the local user. It is not
          always in sync with the current hostname as returned by the
          gethostname(3) system call. If no hostname is configured
          this property will be the empty string. Setting this
          property to the empty string will remove /etc/hostname. This
          property should be an internet-style hostname, 7-bit
          lowercase ASCII, no special chars/spaces.

          The transient (dynamic) hostname is the one configured via
          the kernel's sethostname(3). It can be different from the
          static hostname if DHCP or mDNS have been configured to
          change the name based on network information.  This property
          is never empty. If no hostname is set this will default to

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          "localhost" (configurable at compilation time). Setting this
          property to the empty string will reset the dynamic hostname
          to the static hostname. If no static hostname is configured
          the dynamic hostname will be reset to "localhost". This
          property should be an internet-style hostname, 7-bit
          lowercase ASCII, no special chars/spaces.

          The pretty hostname is a free-form UTF-8 hostname for
          presentation to the user. User interfaces should ensure that
          the pretty hostname and the static hostname stay in sync.
          I.e. when the former is "Lennartcqs Computer" the latter
          should be "lennarts-computer". If no pretty hostname is set
          this setting will be the empty string. Applications should
          then find a suitable fallback, such as the dynamic hostname.

          The icon name is a name following the XDG icon naming spec.
          If not set, information such as the chassis type (see below)
          is used to find a suitable fallback icon name (i.e.
          "computer-laptop" vs.  "computer-desktop" is picked based on
          the chassis information). If no such data is available, the
          empty string is returned. In that case an application should
          fall back to a replacement icon, for example "computer". If
          this property is set to the empty string, the automatic
          fallback name selection is enabled again.

          The chassis type should be one of the currently defined
          chassis types: "desktop", "laptop", "server", "tablet",
          "handset", as well as the special chassis types "vm" and
          "container" for virtualized systems. Note that in most cases
          the chassis type will be determined automatically from
          DMI/SMBIOS/ACPI firmware information. Writing to this
          setting is hence useful only to override misdetected chassis
          types, or to configure the chassis type if it could not be
          auto-detected. Set this property to the empty string to
          reenable the automatic detection of the chassis type from
          firmware information.

          Note that systemd-hostnamed starts only on request and
          terminates after a short idle period. This effectively means
          that PropertyChanged messages are not sent out for changes
          made directly on the files (as in: administrator edits the
          files with vi). This is the intended behavior: manual
          configuration changes should require manual reloading.

          The transient (dynamic) hostname maps directly to the kernel
          hostname. This hostname should be assumed to be highly
          dynamic, and hence should be watched directly, without
          depending on PropertyChanged messages from
          systemd-hostnamed. To accomplish this, open
          /proc/sys/kernel/hostname and poll(3) for SIGHUP which is
          triggered by the kernel every time the hostname changes.
          Again: this is special for the transient (dynamic) hostname,

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          and does not apply to the configured (fixed) hostname.

          Applications may read the hostname data directly if hostname
          change notifications are not necessary. Use gethostname(3),
          /etc/hostname (possibly with per-distribution fallbacks),
          and machine-info(3) for that. For more information on these
          files and syscalls see the respective man pages.

        Methods and Properties
          SetHostname() sets the transient (dynamic) hostname which is
          exposed by the Hostname property. If empty, the transient
          hostname is set to the static hostname.

          SetStaticHostname() sets the static hostname which is
          exposed by the StaticHostname property. If empty, the
          built-in default of "localhost" is used.

          SetPrettyHostname() sets the pretty hostname which is
          exposed by the PrettyHostname property.

          SetIconName(), SetChassis(), SetDeployment(), and
          SetLocation() set the properties IconName (the name of the
          icon representing for the machine), Chassis (the machine
          form factor), Deployment (the system deployment
          environment), and Location (physical system location),
          respectively.

          PrettyHostname, IconName, Chassis, Deployment, and Location
          are stored in /etc/machine-info. See machine-info(5) for the
          semantics of those settings.

          GetProductUUID() returns the "product uuid" as exposed by
          the kernel based on DMI information in
          /sys/class/dmi/id/product_uuid. Reading the file directly
          requires root privileges, and this method allows access to
          unprivileged clients through the polkit framework.

          KernelName, KernelRelease, and KernelVersion expose the
          kernel name (e.g.  "Linux"), release (e.g.  "5.0.0-11"), and
          version (i.e. the build number, e.g.  "#11") as reported by
          uname(2).  OperatingSystemPrettyName,
          OperatingSystemCPEName, and HomeURL expose the PRETTY_NAME=,
          CPE_NAME= and HOME_URL= fields from os-release(5). The
          purpose of those properties is to allow remote clients to
          access this information over D-Bus. Local clients can access
          the information directly.

        Security
          The interactive boolean parameters can be used to control
          whether polkit should interactively ask the user for
          authentication credentials if required.

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          The polkit action for SetHostname() is
          org.freedesktop.hostname1.set-hostname. For
          SetStaticHostname() and SetPrettyHostname() it is
          org.freedesktop.hostname1.set-static-hostname. For
          SetIconName(), SetChassis(), SetDeployment() and
          SetLocation() it is
          org.freedesktop.hostname1.set-machine-info.

     RECOMMENDATIONS
          Here are three examples that show how the pretty hostname
          and the icon name should be used:

          +o   When registering DNS-SD services: use the pretty
              hostname in the service name, and pass the icon name in
              the TXT data, if there is an icon name. Browsing clients
              can then show the server icon on each service. This is
              especially useful for WebDAV applications or UPnP media
              sharing.

          +o   Set the bluetooth name to the pretty hostname.

          +o   When your file browser has a "Computer" icon, replace
              the name with the pretty hostname if set, and the icon
              with the icon name, if it is set.

          To properly handle name lookups with changing local
          hostnames without having to edit /etc/hosts, we recommend
          using systemd-hostnamed in combination with nss-
          myhostname(3).

          A client that wants to change the local hostname for
          DHCP/mDNS should invoke SetHostname("newname", false) as
          soon as the name is available and afterwards reset it via
          SetHostname("").

          Here are some recommendations to follow when generating a
          static (internet) hostname from a pretty name:

          +o   Generate a single DNS label only, not an FQDN. That
              means no dots allowed. Strip them, or replace them with
              "-".

          +o   It's probably safer to not use any non-ASCII chars, even
              if DNS allows this in some way these days. In fact,
              restrict your charset to "a-zA-Z0-9" and "-". Strip
              other chars, or try to replace them in some smart way
              with chars from this set, for example "ä" → "ae", and
              use "-" as the replacement for all punctuation
              characters and whitespace.

          +o   Try to avoid creating repeated "-", as well as "-" as
              the first or last char.

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          +o   Limit the hostname to 63 chars, which is the length of a
              DNS label.

          +o   If after stripping special chars the empty string is the
              result, you can pass this as-is to systemd-hostnamed in
              which case it will automatically use "localhost".

          +o   Uppercase charaacters should be replaced with their
              lowercase equivalents.

          Note that while systemd-hostnamed applies some checks to the
          hostname you pass they are much looser than the
          recommendations above. For example, systemd-hostnamed will
          also accept "_" in the hostname, but we recommend not using
          this to avoid clashes with DNS-SD service types. Also
          systemd-hostnamed allows longer hostnames, but because of
          the DNS label limitations, we recommend not making use of
          this.

          Here are a couple of example conversions:

          +o   "Lennart's PC" → "lennarts-pc"

          +o   "Müllers Computer" → "muellers-computer"

          +o   "Voran!"  → "voran"

          +o   "Es war einmal ein Männlein" →
              "es-war-einmal-ein-maennlein"

          +o   "Jawoll. Ist doch wahr!"  → "jawoll-ist-doch-wahr"

          +o   "レナート" → "localhost"

          +o   "...zack!!! zack!..."  → "zack-zack"

          Of course, an already valid internet hostname label you
          enter and pass through this conversion should stay
          unmodified, so that users have direct control of it, if they
          want - by simply ignoring the fact that the pretty hostname
          is pretty and just edit it as if it was the normal internet
          name.

     VERSIONING
          These D-Bus interfaces follow m[blue]the usual interface
          versioning guidelinesm[][2].

     EXAMPLES
          Example 1. Introspect org.freedesktop.hostname1 on the bus

              $ gdbus introspect --system \
                --dest org.freedesktop.hostname1 \

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                --object-path /org/freedesktop/hostname1

     SEE ALSO
          David Zeuthen's original Fedora m[blue]Feature page about
          xdg-hostnamem[][3]

     NOTES
           1. polkit
              https://www.freedesktop.org/software/polkit/docs/latest/

           2. the usual interface versioning guidelines
              http://0pointer.de/blog/projects/versioning-dbus.html

           3. Feature page about xdg-hostname
              https://fedoraproject.org/wiki/Features/BetterHostname

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