3 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
4 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
5 <!ENTITY % entities SYSTEM
"custom-entities.ent" >
8 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
10 <refentry id=
"org.freedesktop.hostname1" conditional='ENABLE_HOSTNAMED'
11 xmlns:
xi=
"http://www.w3.org/2001/XInclude">
13 <title>org.freedesktop.hostname1
</title>
14 <productname>systemd
</productname>
18 <refentrytitle>org.freedesktop.hostname1
</refentrytitle>
19 <manvolnum>5</manvolnum>
23 <refname>org.freedesktop.hostname1
</refname>
24 <refpurpose>The D-Bus interface of systemd-hostnamed
</refpurpose>
28 <title>Introduction
</title>
31 <citerefentry><refentrytitle>systemd-hostnamed.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
32 is a system service that can be used to control the hostname and related machine metadata from user
33 programs. This page describes the hostname semantics and the D-Bus interface.
</para>
37 <title>The D-Bus API
</title>
39 <para>The service exposes the following interfaces on the bus:
</para>
41 <programlisting executable=
"systemd-hostnamed" node=
"/org/freedesktop/hostname1" interface=
"org.freedesktop.hostname1">
42 node /org/freedesktop/hostname1 {
43 interface org.freedesktop.hostname1 {
45 SetHostname(in s hostname,
47 SetStaticHostname(in s hostname,
49 SetPrettyHostname(in s hostname,
51 SetIconName(in s icon,
53 SetChassis(in s chassis,
55 SetDeployment(in s deployment,
57 SetLocation(in s location,
59 GetProductUUID(in b interactive,
63 readonly s Hostname = '...';
64 readonly s StaticHostname = '...';
65 readonly s PrettyHostname = '...';
66 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
67 readonly s DefaultHostname = '...';
68 readonly s HostnameSource = '...';
69 readonly s IconName = '...';
70 readonly s Chassis = '...';
71 readonly s Deployment = '...';
72 readonly s Location = '...';
73 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
74 readonly s KernelName = '...';
75 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
76 readonly s KernelRelease = '...';
77 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
78 readonly s KernelVersion = '...';
79 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
80 readonly s OperatingSystemPrettyName = '...';
81 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
82 readonly s OperatingSystemCPEName = '...';
83 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
84 readonly s HomeURL = '...';
85 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
86 readonly s HardwareVendor = '...';
87 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
88 readonly s HardwareModel = '...';
90 interface org.freedesktop.DBus.Peer { ... };
91 interface org.freedesktop.DBus.Introspectable { ... };
92 interface org.freedesktop.DBus.Properties { ... };
96 <!--property HardwareVendor is not documented!-->
98 <!--property HardwareModel is not documented!-->
100 <!--Autogenerated cross-references for systemd.directives, do not edit-->
102 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.hostname1"/>
104 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.hostname1"/>
106 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetHostname()"/>
108 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetStaticHostname()"/>
110 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetPrettyHostname()"/>
112 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetIconName()"/>
114 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetChassis()"/>
116 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDeployment()"/>
118 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLocation()"/>
120 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"GetProductUUID()"/>
122 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"Describe()"/>
124 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Hostname"/>
126 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"StaticHostname"/>
128 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"PrettyHostname"/>
130 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DefaultHostname"/>
132 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"HostnameSource"/>
134 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"IconName"/>
136 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Chassis"/>
138 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Deployment"/>
140 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Location"/>
142 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"KernelName"/>
144 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"KernelRelease"/>
146 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"KernelVersion"/>
148 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"OperatingSystemPrettyName"/>
150 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"OperatingSystemCPEName"/>
152 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"HomeURL"/>
154 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"HardwareVendor"/>
156 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"HardwareModel"/>
158 <!--End of Autogenerated section-->
160 <para>Whenever the hostname or other metadata is changed via the daemon,
161 <function>PropertyChanged
</function> signals are sent out to subscribed clients. Changing a hostname
162 using this interface is authenticated via
163 <ulink url=
"https://www.freedesktop.org/software/polkit/docs/latest/">polkit
</ulink>.
</para>
167 <title>Semantics
</title>
169 <para>The
<varname>StaticHostname
</varname> property exposes the
"static" hostname configured in
170 <filename>/etc/hostname
</filename>. It is not always in sync with the current hostname as returned by the
171 <citerefentry project=
"man-pages"><refentrytitle>gethostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
172 system call. If no static hostname is configured this property will be the empty string.
</para>
174 <para>When
<citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry> or
175 <citerefentry><refentrytitle>systemd-hostnamed.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
176 set the hostname, this static hostname
<emphasis>has the highest priority
</emphasis>.
</para>
178 <para>The
<varname>Hostname
</varname> property exposes the actual hostname configured in the kernel via
179 <citerefentry project=
"man-pages"><refentrytitle>sethostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
180 It can be different from the static hostname. This property is never empty.
</para>
182 <para>The
<varname>PrettyHostname
</varname> property exposes the
<emphasis>pretty hostname
</emphasis>
183 which is a free-form UTF-
8 hostname for presentation to the user. User interfaces should ensure that the
184 pretty hostname and the static hostname stay in sync. E.g. when the former is
<literal>Lennart’s
185 Computer
</literal> the latter should be
<literal>lennarts-computer
</literal>. If no pretty hostname is
186 set this setting will be the empty string. Applications should then find a suitable fallback, such as the
187 dynamic hostname.
</para>
189 <para>The
<varname>DefaultHostname
</varname> property exposes the default hostname (configured through
190 <citerefentry><refentrytitle>os-release
</refentrytitle><manvolnum>5</manvolnum></citerefentry>, or a
191 fallback set at compilation time).
</para>
193 <para>The
<varname>HostnameSource
</varname> property exposes the origin of the currently configured
194 hostname. One of
<literal>static
</literal> (set from
<filename>/etc/hostname
</filename>),
195 <literal>transient
</literal> (a non-permanent hostname from an external source),
196 <literal>default
</literal> (the value from
<filename>os-release
</filename> or the the compiled-in
199 <para>The
<varname>IconName
</varname> property exposes the
<emphasis>icon name
</emphasis> following the
200 XDG icon naming spec. If not set, information such as the chassis type (see below) is used to find a
201 suitable fallback icon name (i.e.
<literal>computer-laptop
</literal>
202 vs.
<literal>computer-desktop
</literal> is picked based on the chassis information). If no such data is
203 available, the empty string is returned. In that case an application should fall back to a replacement
204 icon, for example
<literal>computer
</literal>. If this property is set to the empty string, the automatic
205 fallback name selection is enabled again.
</para>
207 <para>The
<varname>Chassis
</varname> property exposes a
<emphasis>chassis type
</emphasis>, one of the
208 currently defined chassis types:
<literal>desktop
</literal>,
<literal>laptop
</literal>,
209 <literal>server
</literal>,
<literal>tablet
</literal>,
<literal>handset
</literal>, as well as the special
210 chassis types
<literal>vm
</literal> and
<literal>container
</literal> for virtualized systems. Note that
211 in most cases the chassis type will be determined automatically from DMI/SMBIOS/ACPI firmware
212 information. Writing to this setting is hence useful only to override misdetected chassis types, or to
213 configure the chassis type if it could not be auto-detected. Set this property to the empty string to
214 reenable the automatic detection of the chassis type from firmware information.
</para>
216 <para>Note that
<filename>systemd-hostnamed
</filename> starts only on request and terminates after a
217 short idle period. This effectively means that
<function>PropertyChanged
</function> messages are not sent
218 out for changes made directly on the files (as in: administrator edits the files with vi). This is
219 the intended behavior: manual configuration changes should require manual reloading.
</para>
221 <para>The transient (dynamic) hostname exposed by the
<varname>Hostname
</varname> property maps directly
222 to the kernel hostname. This hostname should be assumed to be highly dynamic, and hence should be watched
223 directly, without depending on
<function>PropertyChanged
</function> messages from
224 <filename>systemd-hostnamed
</filename>. To accomplish this, open
225 <filename>/proc/sys/kernel/hostname
</filename> and
226 <citerefentry project=
"man-pages"><refentrytitle>poll
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
227 for
<constant>SIGHUP
</constant> which is triggered by the kernel every time the hostname changes. Again:
228 this is special for the transient (dynamic) hostname, and does not apply to the configured (fixed)
231 <para>Applications may read the hostname data directly if hostname change notifications
232 are not necessary. Use
233 <citerefentry project=
"man-pages"><refentrytitle>gethostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
234 <filename>/etc/hostname
</filename> (possibly with per-distribution fallbacks), and
235 <citerefentry><refentrytitle>machine-info
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
236 for that. For more information on these files and syscalls see the respective man pages.
</para>
238 <para><varname>KernelName
</varname>,
<varname>KernelRelease
</varname>, and
239 <varname>KernelVersion
</varname> expose the kernel name (e.g.
<literal>Linux
</literal>), release
240 (e.g.
<literal>5.0.0-
11</literal>), and version (i.e. the build number, e.g.
<literal>#
11</literal>) as
241 reported by
<citerefentry project=
"man-pages"><refentrytitle>uname
</refentrytitle><manvolnum>2</manvolnum></citerefentry>.
242 <varname>OperatingSystemPrettyName
</varname>,
<varname>OperatingSystemCPEName
</varname>, and
243 <varname>HomeURL
</varname> expose the
<varname>PRETTY_NAME=
</varname>,
<varname>CPE_NAME=
</varname> and
244 <varname>HOME_URL=
</varname> fields from
245 <citerefentry><refentrytitle>os-release
</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
246 purpose of those properties is to allow remote clients to access this information over D-Bus. Local
247 clients can access the information directly.
</para>
250 <title>Methods
</title>
252 <para><function>SetHostname()
</function> sets the transient (dynamic) hostname, which is used if no
253 static hostname is set. This value must be an internet-style hostname,
7-bit lowercase ASCII, no
254 special chars/spaces. An empty string will unset the transient hostname.
</para>
256 <para><function>SetStaticHostname()
</function> sets the static hostname which is exposed by the
257 <varname>StaticHostname
</varname> property. When called with an empty argument, the static
258 configuration in
<filename>/etc/hostname
</filename> is removed. Since the static hostname has the
259 highest priority, calling this function usually affects also the
<varname>Hostname
</varname> property
260 and the effective hostname configured in the kernel.
</para>
262 <para><function>SetPrettyHostname()
</function> sets the pretty hostname which is exposed by the
263 <varname>PrettyHostname
</varname> property.
</para>
265 <para><function>SetIconName()
</function>,
<function>SetChassis()
</function>,
266 <function>SetDeployment()
</function>, and
<function>SetLocation()
</function> set the properties
267 <varname>IconName
</varname> (the name of the icon representing for the machine),
268 <varname>Chassis
</varname> (the machine form factor),
<varname>Deployment
</varname> (the system
269 deployment environment), and
<varname>Location
</varname> (physical system location), respectively.
272 <para><varname>PrettyHostname
</varname>,
<varname>IconName
</varname>,
<varname>Chassis
</varname>,
273 <varname>Deployment
</varname>, and
<varname>Location
</varname> are stored in
274 <filename>/etc/machine-info
</filename>. See
275 <citerefentry><refentrytitle>machine-info
</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
276 the semantics of those settings.
</para>
278 <para><function>GetProductUUID()
</function> returns the
"product UUID" as exposed by the kernel based
279 on DMI information in
<filename>/sys/class/dmi/id/product_uuid
</filename>. Reading the file directly
280 requires root privileges, and this method allows access to unprivileged clients through the polkit
283 <para><function>Describe()
</function> returns a JSON representation of all properties in one.
</para>
287 <title>Security
</title>
289 <para>The
<varname>interactive
</varname> boolean parameters can be used to control whether polkit
290 should interactively ask the user for authentication credentials if required.
</para>
292 <para>The polkit action for
<function>SetHostname()
</function> is
293 <interfacename>org.freedesktop.hostname1.set-hostname
</interfacename>. For
294 <function>SetStaticHostname()
</function> and
<function>SetPrettyHostname()
</function> it is
295 <interfacename>org.freedesktop.hostname1.set-static-hostname
</interfacename>. For
296 <function>SetIconName()
</function>,
<function>SetChassis()
</function>,
<function>SetDeployment()
</function>
297 and
<function>SetLocation()
</function> it is
298 <interfacename>org.freedesktop.hostname1.set-machine-info
</interfacename>.
</para>
303 <title>Recommendations
</title>
305 <para>Here are three examples that show how the pretty hostname and the icon name should be used:
307 <listitem><para>When registering DNS-SD services: use the pretty hostname in the service name, and pass
308 the icon name in the TXT data, if there is an icon name. Browsing clients can then show the server icon
309 on each service. This is especially useful for WebDAV applications or UPnP media sharing.
312 <listitem><para>Set the bluetooth name to the pretty hostname.
</para></listitem>
314 <listitem><para>When your file browser has a
"Computer" icon, replace the name with the pretty hostname
315 if set, and the icon with the icon name, if it is set.
</para></listitem>
316 </itemizedlist></para>
318 <para>To properly handle name lookups with changing local hostnames without having to edit
319 <filename>/etc/hosts
</filename>, we recommend using
<filename>systemd-hostnamed
</filename> in combination
320 with
<citerefentry><refentrytitle>nss-myhostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
323 <para>Here are some recommendations to follow when generating a static (internet) hostname from a pretty
326 <listitem><para>Generate a single DNS label only, not an FQDN. That means no dots allowed. Strip them,
327 or replace them with
<literal>-
</literal>.
</para></listitem>
329 <listitem><para>It's probably safer to not use any non-ASCII chars, even if DNS allows this in some way
330 these days. In fact, restrict your charset to
<literal>a-zA-Z0-
9</literal> and
<literal>-
</literal>.
331 Strip other chars, or try to replace them in some smart way with chars from this set, for example
332 <literal>ä
</literal> →
<literal>ae
</literal>, and use
<literal>-
</literal> as the replacement for all
333 punctuation characters and whitespace.
</para></listitem>
335 <listitem><para>Try to avoid creating repeated
<literal>-
</literal>, as well as
<literal>-
</literal> as
336 the first or last char.
</para></listitem>
338 <listitem><para>Limit the hostname to
63 chars, which is the length of a DNS label.
</para></listitem>
340 <listitem><para>If after stripping special chars the empty string is the result, you can pass this
341 as-is to
<filename>systemd-hostnamed
</filename> in which case it will automatically use a suitable
342 fallback.
</para></listitem>
344 <listitem><para>Uppercase charaacters should be replaced with their lowercase equivalents.
346 </itemizedlist></para>
348 <para>Note that while
<filename>systemd-hostnamed
</filename> applies some checks to the hostname you pass
349 they are much looser than the recommendations above. For example,
<filename>systemd-hostnamed
</filename>
350 will also accept
<literal>_
</literal> in the hostname, but we recommend not using this to avoid clashes
351 with DNS-SD service types. Also
<filename>systemd-hostnamed
</filename> allows longer hostnames, but
352 because of the DNS label limitations, we recommend not making use of this.
</para>
354 <para>Here are a couple of example conversions:
356 <listitem><para><literal>Lennart's PC
</literal> →
<literal>lennarts-pc
</literal></para></listitem>
357 <listitem><para><literal>Müllers Computer
</literal> →
<literal>muellers-computer
</literal></para></listitem>
358 <listitem><para><literal>Voran!
</literal> →
<literal>voran
</literal></para></listitem>
359 <listitem><para><literal>Es war einmal ein Männlein
</literal> →
<literal>es-war-einmal-ein-maennlein
</literal></para></listitem>
360 <listitem><para><literal>Jawoll. Ist doch wahr!
</literal> →
<literal>jawoll-ist-doch-wahr
</literal></para></listitem>
361 <listitem><para><literal>レナート
</literal> →
<literal>localhost
</literal></para></listitem>
362 <listitem><para><literal>...zack!!! zack!...
</literal> →
<literal>zack-zack
</literal></para></listitem>
363 </itemizedlist></para>
365 <para>Of course, an already valid internet hostname label you enter and pass through this
366 conversion should stay unmodified, so that users have direct control of it, if they want — by simply
367 ignoring the fact that the pretty hostname is pretty and just edit it as if it was the normal internet
372 <title>Versioning
</title>
374 <para>These D-Bus interfaces follow
<ulink url=
"http://0pointer.de/blog/projects/versioning-dbus.html">
375 the usual interface versioning guidelines
</ulink>.
</para>
379 <title>Examples
</title>
382 <title>Introspect
<interfacename>org.freedesktop.hostname1
</interfacename> on the bus
</title>
384 <programlisting>$ gdbus introspect --system \
385 --dest org.freedesktop.hostname1 \
386 --object-path /org/freedesktop/hostname1
392 <title>See also
</title>
394 <para>David Zeuthen's original Fedora
395 <ulink url=
"https://fedoraproject.org/wiki/Features/BetterHostname">Feature page about xdg-hostname
</ulink></para>