man/org.freedesktop.hostname1.xml - systemd-stable - Rivoreo Source Code Repositories

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   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

 <refentry id="org.freedesktop.hostname1" conditional='ENABLE_HOSTNAMED'
     xmlns:xi="http://www.w3.org/2001/XInclude">
   <refentryinfo>
     <title>org.freedesktop.hostname1</title>
     <productname>systemd</productname>
   </refentryinfo>

   <refmeta>
     <refentrytitle>org.freedesktop.hostname1</refentrytitle>
     <manvolnum>5</manvolnum>
   </refmeta>

   <refnamediv>
     <refname>org.freedesktop.hostname1</refname>
     <refpurpose>The D-Bus interface of systemd-hostnamed</refpurpose>
   </refnamediv>

   <refsect1>
     <title>Introduction</title>

     <para>
     <citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
     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.</para>
   </refsect1>

   <refsect1>
     <title>The D-Bus API</title>

     <para>The service exposes the following interfaces on the bus:</para>

     <programlisting executable="systemd-hostnamed" node="/org/freedesktop/hostname1" interface="org.freedesktop.hostname1">
 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 = '...';
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s HomeURL = '...';
   };
   interface org.freedesktop.DBus.Peer { ... };
   interface org.freedesktop.DBus.Introspectable { ... };
   interface org.freedesktop.DBus.Properties { ... };
 };
     </programlisting>

     <!--Autogenerated cross-references for systemd.directives, do not edit-->

     <variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.hostname1"/>

     <variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.hostname1"/>

     <variablelist class="dbus-method" generated="True" extra-ref="SetHostname()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="SetStaticHostname()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="SetPrettyHostname()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="SetIconName()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="SetChassis()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="SetDeployment()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="SetLocation()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="GetProductUUID()"/>

     <variablelist class="dbus-property" generated="True" extra-ref="Hostname"/>

     <variablelist class="dbus-property" generated="True" extra-ref="StaticHostname"/>

     <variablelist class="dbus-property" generated="True" extra-ref="PrettyHostname"/>

     <variablelist class="dbus-property" generated="True" extra-ref="IconName"/>

     <variablelist class="dbus-property" generated="True" extra-ref="Chassis"/>

     <variablelist class="dbus-property" generated="True" extra-ref="Deployment"/>

     <variablelist class="dbus-property" generated="True" extra-ref="Location"/>

     <variablelist class="dbus-property" generated="True" extra-ref="KernelName"/>

     <variablelist class="dbus-property" generated="True" extra-ref="KernelRelease"/>

     <variablelist class="dbus-property" generated="True" extra-ref="KernelVersion"/>

     <variablelist class="dbus-property" generated="True" extra-ref="OperatingSystemPrettyName"/>

     <variablelist class="dbus-property" generated="True" extra-ref="OperatingSystemCPEName"/>

     <variablelist class="dbus-property" generated="True" extra-ref="HomeURL"/>

     <!--End of Autogenerated section-->

     <para>Whenever the hostname or other metadata is changed via the daemon,
     <function>PropertyChanged</function> signals are sent out to subscribed clients. Changing a hostname
     using this interface is authenticated via
     <ulink url="https://www.freedesktop.org/software/polkit/docs/latest/">polkit</ulink>.</para>
   </refsect1>

   <refsect1>
     <title>Semantics</title>

     <para>The <emphasis>static (configured) hostname</emphasis> is the one configured in
     <filename>/etc/hostname</filename>. It is chosen by the local user. It is not always in sync with the
     current hostname as returned by the
     <citerefentry project="man-pages"><refentrytitle>gethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     system call. If no hostname is configured this property will be the empty string. Setting this property
     to the empty string will remove <filename>/etc/hostname</filename>. This property should be an
     internet-style hostname, 7-bit lowercase ASCII, no special chars/spaces.</para>

     <para>The <emphasis>transient (dynamic) hostname</emphasis> is the one configured via the kernel's
     <citerefentry project="man-pages"><refentrytitle>sethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
     It can be different from the static hostname if DHCP or mDNS have been configured to change the name
     based on network information. <!-- FIXME: it's not DHCP that configures this... -->
     This property is never empty. If no hostname is set this will default to
     <literal>&FALLBACK_HOSTNAME;</literal> (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 <literal>&FALLBACK_HOSTNAME;</literal>. This property
     should be an internet-style hostname, 7-bit lowercase ASCII, no special chars/spaces.</para>

     <para>The <emphasis>pretty hostname</emphasis> 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 <literal>Lennart’s Computer</literal> the latter should be
     <literal>lennarts-computer</literal>. 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.</para>

     <para>The <emphasis>icon name</emphasis> 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. <literal>computer-laptop</literal> vs. <literal>computer-desktop</literal> 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 <literal>computer</literal>. If this property is set
     to the empty string, the automatic fallback name selection is enabled again.</para>

     <para>The <emphasis>chassis type</emphasis> should be one of the currently defined chassis types:
     <literal>desktop</literal>, <literal>laptop</literal>, <literal>server</literal>,
     <literal>tablet</literal>, <literal>handset</literal>, as well as the special chassis types
     <literal>vm</literal> and <literal>container</literal> 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.</para>

     <para>Note that <filename>systemd-hostnamed</filename> starts only on request and terminates after a
     short idle period. This effectively means that <function>PropertyChanged</function> 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.</para>

     <para>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
     <function>PropertyChanged</function> messages from <filename>systemd-hostnamed</filename>. To accomplish
     this, open <filename>/proc/sys/kernel/hostname</filename> and
     <citerefentry project="man-pages"><refentrytitle>poll</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     for <constant>SIGHUP</constant> 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.</para>

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

     <refsect2>
       <title>Methods and Properties</title>

       <para><function>SetHostname()</function> sets the transient (dynamic) hostname which is exposed by the
       <varname>Hostname</varname> property. If empty, the transient hostname is set to the static hostname.
       </para>

       <para><function>SetStaticHostname()</function> sets the static hostname which is exposed by the
       <varname>StaticHostname</varname> property. If empty, the built-in default of
       <literal>&FALLBACK_HOSTNAME;</literal> is used.</para>

       <para><function>SetPrettyHostname()</function> sets the pretty hostname which is exposed by the
       <varname>PrettyHostname</varname> property.</para>

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

       <para><varname>PrettyHostname</varname>, <varname>IconName</varname>, <varname>Chassis</varname>,
       <varname>Deployment</varname>, and <varname>Location</varname> are stored in
       <filename>/etc/machine-info</filename>. See
       <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
       the semantics of those settings.</para>

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

       <para><varname>KernelName</varname>, <varname>KernelRelease</varname>, and
       <varname>KernelVersion</varname> expose the kernel name (e.g. <literal>Linux</literal>), release
       (e.g. <literal>5.0.0-11</literal>), and version (i.e. the build number, e.g. <literal>#11</literal>) as
       reported by
       <citerefentry project="man-pages"><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>.
       <varname>OperatingSystemPrettyName</varname>, <varname>OperatingSystemCPEName</varname>, and
       <varname>HomeURL</varname> expose the <varname>PRETTY_NAME=</varname>, <varname>CPE_NAME=</varname> and
       <varname>HOME_URL=</varname> fields from
       <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
       purpose of those properties is to allow remote clients to access this information over D-Bus. Local
       clients can access the information directly.</para>
     </refsect2>

     <refsect2>
       <title>Security</title>

       <para>The <varname>interactive</varname> boolean parameters can be used to control whether polkit
       should interactively ask the user for authentication credentials if required.</para>

       <para>The polkit action for <function>SetHostname()</function> is
       <interfacename>org.freedesktop.hostname1.set-hostname</interfacename>. For
       <function>SetStaticHostname()</function> and <function>SetPrettyHostname()</function> it is
       <interfacename>org.freedesktop.hostname1.set-static-hostname</interfacename>. For
       <function>SetIconName()</function>, <function>SetChassis()</function>, <function>SetDeployment()</function>
       and <function>SetLocation()</function> it is
       <interfacename>org.freedesktop.hostname1.set-machine-info</interfacename>.</para>
     </refsect2>
   </refsect1>

   <refsect1>
     <title>Recommendations</title>

     <para>Here are three examples that show how the pretty hostname and the icon name should be used:
     <itemizedlist>
       <listitem><para>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.
       </para></listitem>

       <listitem><para>Set the bluetooth name to the pretty hostname.</para></listitem>

       <listitem><para>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.</para></listitem>
     </itemizedlist></para>

     <para>To properly handle name lookups with changing local hostnames without having to edit
     <filename>/etc/hosts</filename>, we recommend using <filename>systemd-hostnamed</filename> in combination
     with <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
     </para>

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

     <para>Here are some recommendations to follow when generating a static (internet) hostname from a pretty
     name:
     <itemizedlist>
       <listitem><para>Generate a single DNS label only, not an FQDN. That means no dots allowed. Strip them,
       or replace them with <literal>-</literal>.</para></listitem>

       <listitem><para>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 <literal>a-zA-Z0-9</literal> and <literal>-</literal>.
       Strip other chars, or try to replace them in some smart way with chars from this set, for example
       <literal>ä</literal> → <literal>ae</literal>, and use <literal>-</literal> as the replacement for all
       punctuation characters and whitespace.</para></listitem>

       <listitem><para>Try to avoid creating repeated <literal>-</literal>, as well as <literal>-</literal> as
       the first or last char.</para></listitem>

       <listitem><para>Limit the hostname to 63 chars, which is the length of a DNS label.</para></listitem>

       <listitem><para>If after stripping special chars the empty string is the result, you can pass this
       as-is to <filename>systemd-hostnamed</filename> in which case it will automatically use
       <literal>&FALLBACK_HOSTNAME;</literal>.</para></listitem>

       <listitem><para>Uppercase charaacters should be replaced with their lowercase equivalents.
       </para></listitem>
     </itemizedlist></para>

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

     <para>Here are a couple of example conversions:
     <itemizedlist>
       <listitem><para><literal>Lennart's PC</literal> → <literal>lennarts-pc</literal></para></listitem>
       <listitem><para><literal>Müllers Computer</literal> → <literal>muellers-computer</literal></para></listitem>
       <listitem><para><literal>Voran!</literal> → <literal>voran</literal></para></listitem>
       <listitem><para><literal>Es war einmal ein Männlein</literal> → <literal>es-war-einmal-ein-maennlein</literal></para></listitem>
       <listitem><para><literal>Jawoll. Ist doch wahr!</literal> → <literal>jawoll-ist-doch-wahr</literal></para></listitem>
       <listitem><para><literal>レナート</literal> → <literal>localhost</literal></para></listitem>
       <listitem><para><literal>...zack!!! zack!...</literal> → <literal>zack-zack</literal></para></listitem>
     </itemizedlist></para>

     <para>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.</para>
   </refsect1>

   <refsect1>
     <title>Versioning</title>

     <para>These D-Bus interfaces follow <ulink url="http://0pointer.de/blog/projects/versioning-dbus.html">
     the usual interface versioning guidelines</ulink>.</para>
   </refsect1>

   <refsect1>
     <title>Examples</title>

     <example>
       <title>Introspect <interfacename>org.freedesktop.hostname1</interfacename> on the bus</title>

       <programlisting>$ gdbus introspect --system \
   --dest org.freedesktop.hostname1 \
   --object-path /org/freedesktop/hostname1
       </programlisting>
     </example>
   </refsect1>

   <refsect1>
     <title>See also</title>

     <para>David Zeuthen's original Fedora
     <ulink url="https://fedoraproject.org/wiki/Features/BetterHostname">Feature page about xdg-hostname</ulink></para>
   </refsect1>
 </refentry>
	<?xml version="1.0"?>
	<!---nxml--->
	<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
	<!ENTITY % entities SYSTEM "custom-entities.ent" >
	%entities;
	]>
	<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

	<refentry id="org.freedesktop.hostname1" conditional='ENABLE_HOSTNAMED'
	xmlns:xi="http://www.w3.org/2001/XInclude">
	<refentryinfo>
	<title>org.freedesktop.hostname1</title>
	<productname>systemd</productname>
	</refentryinfo>

	<refmeta>
	<refentrytitle>org.freedesktop.hostname1</refentrytitle>
	<manvolnum>5</manvolnum>
	</refmeta>

	<refnamediv>
	<refname>org.freedesktop.hostname1</refname>
	<refpurpose>The D-Bus interface of systemd-hostnamed</refpurpose>
	</refnamediv>

	<refsect1>
	<title>Introduction</title>

	<para>
	<citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
	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.</para>
	</refsect1>

	<refsect1>
	<title>The D-Bus API</title>

	<para>The service exposes the following interfaces on the bus:</para>

	<programlisting executable="systemd-hostnamed" node="/org/freedesktop/hostname1" interface="org.freedesktop.hostname1">
	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 = '...';
	@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
	readonly s HomeURL = '...';
	};
	interface org.freedesktop.DBus.Peer { ... };
	interface org.freedesktop.DBus.Introspectable { ... };
	interface org.freedesktop.DBus.Properties { ... };
	};
	</programlisting>

	<!--Autogenerated cross-references for systemd.directives, do not edit-->

	<variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.hostname1"/>

	<variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.hostname1"/>

	<variablelist class="dbus-method" generated="True" extra-ref="SetHostname()"/>

	<variablelist class="dbus-method" generated="True" extra-ref="SetStaticHostname()"/>

	<variablelist class="dbus-method" generated="True" extra-ref="SetPrettyHostname()"/>

	<variablelist class="dbus-method" generated="True" extra-ref="SetIconName()"/>

	<variablelist class="dbus-method" generated="True" extra-ref="SetChassis()"/>

	<variablelist class="dbus-method" generated="True" extra-ref="SetDeployment()"/>

	<variablelist class="dbus-method" generated="True" extra-ref="SetLocation()"/>

	<variablelist class="dbus-method" generated="True" extra-ref="GetProductUUID()"/>

	<variablelist class="dbus-property" generated="True" extra-ref="Hostname"/>

	<variablelist class="dbus-property" generated="True" extra-ref="StaticHostname"/>

	<variablelist class="dbus-property" generated="True" extra-ref="PrettyHostname"/>

	<variablelist class="dbus-property" generated="True" extra-ref="IconName"/>

	<variablelist class="dbus-property" generated="True" extra-ref="Chassis"/>

	<variablelist class="dbus-property" generated="True" extra-ref="Deployment"/>

	<variablelist class="dbus-property" generated="True" extra-ref="Location"/>

	<variablelist class="dbus-property" generated="True" extra-ref="KernelName"/>

	<variablelist class="dbus-property" generated="True" extra-ref="KernelRelease"/>

	<variablelist class="dbus-property" generated="True" extra-ref="KernelVersion"/>

	<variablelist class="dbus-property" generated="True" extra-ref="OperatingSystemPrettyName"/>

	<variablelist class="dbus-property" generated="True" extra-ref="OperatingSystemCPEName"/>

	<variablelist class="dbus-property" generated="True" extra-ref="HomeURL"/>

	<!--End of Autogenerated section-->

	<para>Whenever the hostname or other metadata is changed via the daemon,
	<function>PropertyChanged</function> signals are sent out to subscribed clients. Changing a hostname
	using this interface is authenticated via
	<ulink url="https://www.freedesktop.org/software/polkit/docs/latest/">polkit</ulink>.</para>
	</refsect1>

	<refsect1>
	<title>Semantics</title>

	<para>The <emphasis>static (configured) hostname</emphasis> is the one configured in
	<filename>/etc/hostname</filename>. It is chosen by the local user. It is not always in sync with the
	current hostname as returned by the
	<citerefentry project="man-pages"><refentrytitle>gethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	system call. If no hostname is configured this property will be the empty string. Setting this property
	to the empty string will remove <filename>/etc/hostname</filename>. This property should be an
	internet-style hostname, 7-bit lowercase ASCII, no special chars/spaces.</para>

	<para>The <emphasis>transient (dynamic) hostname</emphasis> is the one configured via the kernel's
	<citerefentry project="man-pages"><refentrytitle>sethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
	It can be different from the static hostname if DHCP or mDNS have been configured to change the name
	based on network information. <!-- FIXME: it's not DHCP that configures this... -->
	This property is never empty. If no hostname is set this will default to
	<literal>&FALLBACK_HOSTNAME;</literal> (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 <literal>&FALLBACK_HOSTNAME;</literal>. This property
	should be an internet-style hostname, 7-bit lowercase ASCII, no special chars/spaces.</para>

	<para>The <emphasis>pretty hostname</emphasis> 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 <literal>Lennart’s Computer</literal> the latter should be
	<literal>lennarts-computer</literal>. 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.</para>

	<para>The <emphasis>icon name</emphasis> 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. <literal>computer-laptop</literal> vs. <literal>computer-desktop</literal> 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 <literal>computer</literal>. If this property is set
	to the empty string, the automatic fallback name selection is enabled again.</para>

	<para>The <emphasis>chassis type</emphasis> should be one of the currently defined chassis types:
	<literal>desktop</literal>, <literal>laptop</literal>, <literal>server</literal>,
	<literal>tablet</literal>, <literal>handset</literal>, as well as the special chassis types
	<literal>vm</literal> and <literal>container</literal> 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.</para>

	<para>Note that <filename>systemd-hostnamed</filename> starts only on request and terminates after a
	short idle period. This effectively means that <function>PropertyChanged</function> 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.</para>

	<para>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
	<function>PropertyChanged</function> messages from <filename>systemd-hostnamed</filename>. To accomplish
	this, open <filename>/proc/sys/kernel/hostname</filename> and
	<citerefentry project="man-pages"><refentrytitle>poll</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	for <constant>SIGHUP</constant> 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.</para>

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

	<refsect2>
	<title>Methods and Properties</title>

	<para><function>SetHostname()</function> sets the transient (dynamic) hostname which is exposed by the
	<varname>Hostname</varname> property. If empty, the transient hostname is set to the static hostname.
	</para>

	<para><function>SetStaticHostname()</function> sets the static hostname which is exposed by the
	<varname>StaticHostname</varname> property. If empty, the built-in default of
	<literal>&FALLBACK_HOSTNAME;</literal> is used.</para>

	<para><function>SetPrettyHostname()</function> sets the pretty hostname which is exposed by the
	<varname>PrettyHostname</varname> property.</para>

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

	<para><varname>PrettyHostname</varname>, <varname>IconName</varname>, <varname>Chassis</varname>,
	<varname>Deployment</varname>, and <varname>Location</varname> are stored in
	<filename>/etc/machine-info</filename>. See
	<citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
	the semantics of those settings.</para>

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

	<para><varname>KernelName</varname>, <varname>KernelRelease</varname>, and
	<varname>KernelVersion</varname> expose the kernel name (e.g. <literal>Linux</literal>), release
	(e.g. <literal>5.0.0-11</literal>), and version (i.e. the build number, e.g. <literal>#11</literal>) as
	reported by
	<citerefentry project="man-pages"><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>.
	<varname>OperatingSystemPrettyName</varname>, <varname>OperatingSystemCPEName</varname>, and
	<varname>HomeURL</varname> expose the <varname>PRETTY_NAME=</varname>, <varname>CPE_NAME=</varname> and
	<varname>HOME_URL=</varname> fields from
	<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
	purpose of those properties is to allow remote clients to access this information over D-Bus. Local
	clients can access the information directly.</para>
	</refsect2>

	<refsect2>
	<title>Security</title>

	<para>The <varname>interactive</varname> boolean parameters can be used to control whether polkit
	should interactively ask the user for authentication credentials if required.</para>

	<para>The polkit action for <function>SetHostname()</function> is
	<interfacename>org.freedesktop.hostname1.set-hostname</interfacename>. For
	<function>SetStaticHostname()</function> and <function>SetPrettyHostname()</function> it is
	<interfacename>org.freedesktop.hostname1.set-static-hostname</interfacename>. For
	<function>SetIconName()</function>, <function>SetChassis()</function>, <function>SetDeployment()</function>
	and <function>SetLocation()</function> it is
	<interfacename>org.freedesktop.hostname1.set-machine-info</interfacename>.</para>
	</refsect2>
	</refsect1>

	<refsect1>
	<title>Recommendations</title>

	<para>Here are three examples that show how the pretty hostname and the icon name should be used:
	<itemizedlist>
	<listitem><para>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.
	</para></listitem>

	<listitem><para>Set the bluetooth name to the pretty hostname.</para></listitem>

	<listitem><para>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.</para></listitem>
	</itemizedlist></para>

	<para>To properly handle name lookups with changing local hostnames without having to edit
	<filename>/etc/hosts</filename>, we recommend using <filename>systemd-hostnamed</filename> in combination
	with <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
	</para>

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

	<para>Here are some recommendations to follow when generating a static (internet) hostname from a pretty
	name:
	<itemizedlist>
	<listitem><para>Generate a single DNS label only, not an FQDN. That means no dots allowed. Strip them,
	or replace them with <literal>-</literal>.</para></listitem>

	<listitem><para>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 <literal>a-zA-Z0-9</literal> and <literal>-</literal>.
	Strip other chars, or try to replace them in some smart way with chars from this set, for example
	<literal>ä</literal> → <literal>ae</literal>, and use <literal>-</literal> as the replacement for all
	punctuation characters and whitespace.</para></listitem>

	<listitem><para>Try to avoid creating repeated <literal>-</literal>, as well as <literal>-</literal> as
	the first or last char.</para></listitem>

	<listitem><para>Limit the hostname to 63 chars, which is the length of a DNS label.</para></listitem>

	<listitem><para>If after stripping special chars the empty string is the result, you can pass this
	as-is to <filename>systemd-hostnamed</filename> in which case it will automatically use
	<literal>&FALLBACK_HOSTNAME;</literal>.</para></listitem>

	<listitem><para>Uppercase charaacters should be replaced with their lowercase equivalents.
	</para></listitem>
	</itemizedlist></para>

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

	<para>Here are a couple of example conversions:
	<itemizedlist>
	<listitem><para><literal>Lennart's PC</literal> → <literal>lennarts-pc</literal></para></listitem>
	<listitem><para><literal>Müllers Computer</literal> → <literal>muellers-computer</literal></para></listitem>
	<listitem><para><literal>Voran!</literal> → <literal>voran</literal></para></listitem>
	<listitem><para><literal>Es war einmal ein Männlein</literal> → <literal>es-war-einmal-ein-maennlein</literal></para></listitem>
	<listitem><para><literal>Jawoll. Ist doch wahr!</literal> → <literal>jawoll-ist-doch-wahr</literal></para></listitem>
	<listitem><para><literal>レナート</literal> → <literal>localhost</literal></para></listitem>
	<listitem><para><literal>...zack!!! zack!...</literal> → <literal>zack-zack</literal></para></listitem>
	</itemizedlist></para>

	<para>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.</para>
	</refsect1>

	<refsect1>
	<title>Versioning</title>

	<para>These D-Bus interfaces follow <ulink url="http://0pointer.de/blog/projects/versioning-dbus.html">
	the usual interface versioning guidelines</ulink>.</para>
	</refsect1>

	<refsect1>
	<title>Examples</title>

	<example>
	<title>Introspect <interfacename>org.freedesktop.hostname1</interfacename> on the bus</title>

	<programlisting>$ gdbus introspect --system \
	--dest org.freedesktop.hostname1 \
	--object-path /org/freedesktop/hostname1
	</programlisting>
	</example>
	</refsect1>

	<refsect1>
	<title>See also</title>

	<para>David Zeuthen's original Fedora
	<ulink url="https://fedoraproject.org/wiki/Features/BetterHostname">Feature page about xdg-hostname</ulink></para>
	</refsect1>
	</refentry>