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,
62 readonly s Hostname = '...';
63 readonly s StaticHostname = '...';
64 readonly s PrettyHostname = '...';
65 readonly s IconName = '...';
66 readonly s Chassis = '...';
67 readonly s Deployment = '...';
68 readonly s Location = '...';
69 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
70 readonly s KernelName = '...';
71 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
72 readonly s KernelRelease = '...';
73 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
74 readonly s KernelVersion = '...';
75 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
76 readonly s OperatingSystemPrettyName = '...';
77 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
78 readonly s OperatingSystemCPEName = '...';
79 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
80 readonly s HomeURL = '...';
82 interface org.freedesktop.DBus.Peer { ... };
83 interface org.freedesktop.DBus.Introspectable { ... };
84 interface org.freedesktop.DBus.Properties { ... };
88 <!--Autogenerated cross-references for systemd.directives, do not edit-->
90 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.hostname1"/>
92 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.hostname1"/>
94 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetHostname()"/>
96 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetStaticHostname()"/>
98 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetPrettyHostname()"/>
100 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetIconName()"/>
102 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetChassis()"/>
104 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDeployment()"/>
106 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLocation()"/>
108 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"GetProductUUID()"/>
110 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Hostname"/>
112 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"StaticHostname"/>
114 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"PrettyHostname"/>
116 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"IconName"/>
118 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Chassis"/>
120 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Deployment"/>
122 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Location"/>
124 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"KernelName"/>
126 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"KernelRelease"/>
128 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"KernelVersion"/>
130 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"OperatingSystemPrettyName"/>
132 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"OperatingSystemCPEName"/>
134 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"HomeURL"/>
136 <!--End of Autogenerated section-->
138 <para>Whenever the hostname or other metadata is changed via the daemon,
139 <function>PropertyChanged
</function> signals are sent out to subscribed clients. Changing a hostname
140 using this interface is authenticated via
141 <ulink url=
"https://www.freedesktop.org/software/polkit/docs/latest/">polkit
</ulink>.
</para>
145 <title>Semantics
</title>
147 <para>The
<varname>StaticHostname
</varname> property exposes the
"static" hostname configured in
148 <filename>/etc/hostname
</filename>. It is not always in sync with the current hostname as returned by the
149 <citerefentry project=
"man-pages"><refentrytitle>gethostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
150 system call. If no static hostname is configured this property will be the empty string.
</para>
152 <para>When
<citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry> or
153 <citerefentry><refentrytitle>systemd-hostnamed.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
154 set the hostname, this static hostname
<emphasis>has the highest priority
</emphasis>.
</para>
156 <para>The
<varname>Hostname
</varname> property exposes the actual hostname configured in the kernel via
157 <citerefentry project=
"man-pages"><refentrytitle>sethostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
158 It can be different from the static hostname. This property is never empty.
</para>
160 <para>The
<varname>PrettyHostname
</varname> property exposes the
<emphasis>pretty hostname
</emphasis>
161 which is a free-form UTF-
8 hostname for presentation to the user. User interfaces should ensure that the
162 pretty hostname and the static hostname stay in sync. E.g. when the former is
<literal>Lennart’s
163 Computer
</literal> the latter should be
<literal>lennarts-computer
</literal>. If no pretty hostname is
164 set this setting will be the empty string. Applications should then find a suitable fallback, such as the
165 dynamic hostname.
</para>
167 <para>The
<varname>IconName
</varname> property exposes the
<emphasis>icon name
</emphasis> following the
168 XDG icon naming spec. If not set, information such as the chassis type (see below) is used to find a
169 suitable fallback icon name (i.e.
<literal>computer-laptop
</literal>
170 vs.
<literal>computer-desktop
</literal> is picked based on the chassis information). If no such data is
171 available, the empty string is returned. In that case an application should fall back to a replacement
172 icon, for example
<literal>computer
</literal>. If this property is set to the empty string, the automatic
173 fallback name selection is enabled again.
</para>
175 <para>The
<varname>Chassis
</varname> property exposes a
<emphasis>chassis type
</emphasis>, one of the
176 currently defined chassis types:
<literal>desktop
</literal>,
<literal>laptop
</literal>,
177 <literal>server
</literal>,
<literal>tablet
</literal>,
<literal>handset
</literal>, as well as the special
178 chassis types
<literal>vm
</literal> and
<literal>container
</literal> for virtualized systems. Note that
179 in most cases the chassis type will be determined automatically from DMI/SMBIOS/ACPI firmware
180 information. Writing to this setting is hence useful only to override misdetected chassis types, or to
181 configure the chassis type if it could not be auto-detected. Set this property to the empty string to
182 reenable the automatic detection of the chassis type from firmware information.
</para>
184 <para>Note that
<filename>systemd-hostnamed
</filename> starts only on request and terminates after a
185 short idle period. This effectively means that
<function>PropertyChanged
</function> messages are not sent
186 out for changes made directly on the files (as in: administrator edits the files with vi). This is
187 the intended behavior: manual configuration changes should require manual reloading.
</para>
189 <para>The transient (dynamic) hostname exposed by the
<varname>Hostname
</varname> property maps directly
190 to the kernel hostname. This hostname should be assumed to be highly dynamic, and hence should be watched
191 directly, without depending on
<function>PropertyChanged
</function> messages from
192 <filename>systemd-hostnamed
</filename>. To accomplish this, open
193 <filename>/proc/sys/kernel/hostname
</filename> and
194 <citerefentry project=
"man-pages"><refentrytitle>poll
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
195 for
<constant>SIGHUP
</constant> which is triggered by the kernel every time the hostname changes. Again:
196 this is special for the transient (dynamic) hostname, and does not apply to the configured (fixed)
199 <para>Applications may read the hostname data directly if hostname change notifications
200 are not necessary. Use
201 <citerefentry project=
"man-pages"><refentrytitle>gethostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
202 <filename>/etc/hostname
</filename> (possibly with per-distribution fallbacks), and
203 <citerefentry><refentrytitle>machine-info
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
204 for that. For more information on these files and syscalls see the respective man pages.
</para>
207 <title>Methods
</title>
209 <para><function>SetHostname()
</function> sets the transient (dynamic) hostname, which is used if no
210 static hostname is set. This value must be an internet-style hostname,
7-bit lowercase ASCII, no
211 special chars/spaces. An empty string will unset the transient hostname.
</para>
213 <para><function>SetStaticHostname()
</function> sets the static hostname which is exposed by the
214 <varname>StaticHostname
</varname> property. When called with an empty argument, the static
215 configuration in
<filename>/etc/hostname
</filename> is removed. Since the static hostname has the
216 highest priority, calling this function usually affects also the
<varname>Hostname
</varname> property
217 and the effective hostname configured in the kernel.
</para>
219 <para><function>SetPrettyHostname()
</function> sets the pretty hostname which is exposed by the
220 <varname>PrettyHostname
</varname> property.
</para>
222 <para><function>SetIconName()
</function>,
<function>SetChassis()
</function>,
223 <function>SetDeployment()
</function>, and
<function>SetLocation()
</function> set the properties
224 <varname>IconName
</varname> (the name of the icon representing for the machine),
225 <varname>Chassis
</varname> (the machine form factor),
<varname>Deployment
</varname> (the system
226 deployment environment), and
<varname>Location
</varname> (physical system location), respectively.
229 <para><varname>PrettyHostname
</varname>,
<varname>IconName
</varname>,
<varname>Chassis
</varname>,
230 <varname>Deployment
</varname>, and
<varname>Location
</varname> are stored in
231 <filename>/etc/machine-info
</filename>. See
232 <citerefentry><refentrytitle>machine-info
</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
233 the semantics of those settings.
</para>
235 <para><function>GetProductUUID()
</function> returns the
"product uuid" as exposed by the kernel based
236 on DMI information in
<filename>/sys/class/dmi/id/product_uuid
</filename>. Reading the file directly
237 requires root privileges, and this method allows access to unprivileged clients through the polkit
240 <para><varname>KernelName
</varname>,
<varname>KernelRelease
</varname>, and
241 <varname>KernelVersion
</varname> expose the kernel name (e.g.
<literal>Linux
</literal>), release
242 (e.g.
<literal>5.0.0-
11</literal>), and version (i.e. the build number, e.g.
<literal>#
11</literal>) as
244 <citerefentry project=
"man-pages"><refentrytitle>uname
</refentrytitle><manvolnum>2</manvolnum></citerefentry>.
245 <varname>OperatingSystemPrettyName
</varname>,
<varname>OperatingSystemCPEName
</varname>, and
246 <varname>HomeURL
</varname> expose the
<varname>PRETTY_NAME=
</varname>,
<varname>CPE_NAME=
</varname> and
247 <varname>HOME_URL=
</varname> fields from
248 <citerefentry><refentrytitle>os-release
</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
249 purpose of those properties is to allow remote clients to access this information over D-Bus. Local
250 clients can access the information directly.
</para>
254 <title>Security
</title>
256 <para>The
<varname>interactive
</varname> boolean parameters can be used to control whether polkit
257 should interactively ask the user for authentication credentials if required.
</para>
259 <para>The polkit action for
<function>SetHostname()
</function> is
260 <interfacename>org.freedesktop.hostname1.set-hostname
</interfacename>. For
261 <function>SetStaticHostname()
</function> and
<function>SetPrettyHostname()
</function> it is
262 <interfacename>org.freedesktop.hostname1.set-static-hostname
</interfacename>. For
263 <function>SetIconName()
</function>,
<function>SetChassis()
</function>,
<function>SetDeployment()
</function>
264 and
<function>SetLocation()
</function> it is
265 <interfacename>org.freedesktop.hostname1.set-machine-info
</interfacename>.
</para>
270 <title>Recommendations
</title>
272 <para>Here are three examples that show how the pretty hostname and the icon name should be used:
274 <listitem><para>When registering DNS-SD services: use the pretty hostname in the service name, and pass
275 the icon name in the TXT data, if there is an icon name. Browsing clients can then show the server icon
276 on each service. This is especially useful for WebDAV applications or UPnP media sharing.
279 <listitem><para>Set the bluetooth name to the pretty hostname.
</para></listitem>
281 <listitem><para>When your file browser has a
"Computer" icon, replace the name with the pretty hostname
282 if set, and the icon with the icon name, if it is set.
</para></listitem>
283 </itemizedlist></para>
285 <para>To properly handle name lookups with changing local hostnames without having to edit
286 <filename>/etc/hosts
</filename>, we recommend using
<filename>systemd-hostnamed
</filename> in combination
287 with
<citerefentry><refentrytitle>nss-myhostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
290 <para>Here are some recommendations to follow when generating a static (internet) hostname from a pretty
293 <listitem><para>Generate a single DNS label only, not an FQDN. That means no dots allowed. Strip them,
294 or replace them with
<literal>-
</literal>.
</para></listitem>
296 <listitem><para>It's probably safer to not use any non-ASCII chars, even if DNS allows this in some way
297 these days. In fact, restrict your charset to
<literal>a-zA-Z0-
9</literal> and
<literal>-
</literal>.
298 Strip other chars, or try to replace them in some smart way with chars from this set, for example
299 <literal>ä
</literal> →
<literal>ae
</literal>, and use
<literal>-
</literal> as the replacement for all
300 punctuation characters and whitespace.
</para></listitem>
302 <listitem><para>Try to avoid creating repeated
<literal>-
</literal>, as well as
<literal>-
</literal> as
303 the first or last char.
</para></listitem>
305 <listitem><para>Limit the hostname to
63 chars, which is the length of a DNS label.
</para></listitem>
307 <listitem><para>If after stripping special chars the empty string is the result, you can pass this
308 as-is to
<filename>systemd-hostnamed
</filename> in which case it will automatically use
309 <literal>&FALLBACK_HOSTNAME;</literal>.
</para></listitem>
311 <listitem><para>Uppercase charaacters should be replaced with their lowercase equivalents.
313 </itemizedlist></para>
315 <para>Note that while
<filename>systemd-hostnamed
</filename> applies some checks to the hostname you pass
316 they are much looser than the recommendations above. For example,
<filename>systemd-hostnamed
</filename>
317 will also accept
<literal>_
</literal> in the hostname, but we recommend not using this to avoid clashes
318 with DNS-SD service types. Also
<filename>systemd-hostnamed
</filename> allows longer hostnames, but
319 because of the DNS label limitations, we recommend not making use of this.
</para>
321 <para>Here are a couple of example conversions:
323 <listitem><para><literal>Lennart's PC
</literal> →
<literal>lennarts-pc
</literal></para></listitem>
324 <listitem><para><literal>Müllers Computer
</literal> →
<literal>muellers-computer
</literal></para></listitem>
325 <listitem><para><literal>Voran!
</literal> →
<literal>voran
</literal></para></listitem>
326 <listitem><para><literal>Es war einmal ein Männlein
</literal> →
<literal>es-war-einmal-ein-maennlein
</literal></para></listitem>
327 <listitem><para><literal>Jawoll. Ist doch wahr!
</literal> →
<literal>jawoll-ist-doch-wahr
</literal></para></listitem>
328 <listitem><para><literal>レナート
</literal> →
<literal>localhost
</literal></para></listitem>
329 <listitem><para><literal>...zack!!! zack!...
</literal> →
<literal>zack-zack
</literal></para></listitem>
330 </itemizedlist></para>
332 <para>Of course, an already valid internet hostname label you enter and pass through this
333 conversion should stay unmodified, so that users have direct control of it, if they want — by simply
334 ignoring the fact that the pretty hostname is pretty and just edit it as if it was the normal internet
339 <title>Versioning
</title>
341 <para>These D-Bus interfaces follow
<ulink url=
"http://0pointer.de/blog/projects/versioning-dbus.html">
342 the usual interface versioning guidelines
</ulink>.
</para>
346 <title>Examples
</title>
349 <title>Introspect
<interfacename>org.freedesktop.hostname1
</interfacename> on the bus
</title>
351 <programlisting>$ gdbus introspect --system \
352 --dest org.freedesktop.hostname1 \
353 --object-path /org/freedesktop/hostname1
359 <title>See also
</title>
361 <para>David Zeuthen's original Fedora
362 <ulink url=
"https://fedoraproject.org/wiki/Features/BetterHostname">Feature page about xdg-hostname
</ulink></para>