org.freedesktop.hostname1(5) — Linux manual page

NAME | INTRODUCTION | THE D-BUS API | SEMANTICS | RECOMMENDATIONS | VERSIONING | EXAMPLES | SEE ALSO | NOTES | COLOPHON

ORG.FREEDESKTOP.HOSTNAME1(5)freedesktop.hostname1REEDESKTOP.HOSTNAME1(5)

NAME         top

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

INTRODUCTION         top

       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         top

       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);
                 Describe(out s json);
               properties:
                 readonly s Hostname = '...';
                 readonly s StaticHostname = '...';
                 readonly s PrettyHostname = '...';
                 @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                 readonly s DefaultHostname = '...';
                 readonly s HostnameSource = '...';
                 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 = '...';
                 @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                 readonly s HomeURL = '...';
                 @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                 readonly s HardwareVendor = '...';
                 @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
                 readonly s HardwareModel = '...';
             };
             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 polkit[1].

SEMANTICS         top

       The StaticHostname property exposes the "static" hostname
       configured in /etc/hostname. It is not always in sync with the
       current hostname as returned by the gethostname(3) system call.
       If no static hostname is configured this property will be the
       empty string.

       When systemd(1) or systemd-hostnamed.service(8) set the hostname,
       this static hostname has the highest priority.

       The Hostname property exposes the actual hostname configured in
       the kernel via sethostname(3). It can be different from the
       static hostname. This property is never empty.

       The PrettyHostname property exposes the pretty hostname which 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. E.g. when the former is "Lennart’s
       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 DefaultHostname property exposes the default hostname
       (configured through os-release(5), or a fallback set at
       compilation time).

       The HostnameSource property exposes the origin of the currently
       configured hostname. One of "static" (set from /etc/hostname),
       "transient" (a non-permanent hostname from an external source),
       "default" (the value from os-release or the compiled-in
       fallback).

       The IconName property exposes the icon 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 property exposes a chassis type, 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 exposed by the Hostname property
       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, 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.

       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.

   Methods
       SetHostname() sets the transient (dynamic) hostname, which is
       used if no static hostname is set. This value must be an
       internet-style hostname, 7-bit lowercase ASCII, no special
       chars/spaces. An empty string will unset the transient hostname.

       SetStaticHostname() sets the static hostname which is exposed by
       the StaticHostname property. When called with an empty argument,
       the static configuration in /etc/hostname is removed. Since the
       static hostname has the highest priority, calling this function
       usually affects also the Hostname property and the effective
       hostname configured in the kernel.

       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.

       Describe() returns a JSON representation of all properties in
       one.

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

       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         top

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

       •   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.

       •   Set the bluetooth name to the pretty hostname.

       •   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).

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

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

       •   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.

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

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

       •   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 a suitable fallback.

       •   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:

       •   "Lennart's PC" → "lennarts-pc"

       •   "Müllers Computer" → "muellers-computer"

       •   "Voran!"  → "voran"

       •   "Es war einmal ein Männlein" → "es-war-einmal-ein-maennlein"

       •   "Jawoll. Ist doch wahr!"  → "jawoll-ist-doch-wahr"

       •   "レナート" → "localhost"

       •   "...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         top

       These D-Bus interfaces follow the usual interface versioning
       guidelines[2].

EXAMPLES         top

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

           $ gdbus introspect --system \
             --dest org.freedesktop.hostname1 \
             --object-path /org/freedesktop/hostname1

SEE ALSO         top

       David Zeuthen's original Fedora Feature page about
       xdg-hostname[3]

NOTES         top

        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

COLOPHON         top

       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 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-27.)  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 249                                 ORG.FREEDESKTOP.HOSTNAME1(5)

Pages that refer to this page: os-release(5)systemd-hostnamed.service(8)