man: import org.freedesktop.hostname1(3) from the wiki
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
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<!ENTITY systemenvgeneratordir @SYSTEM_ENV_GENERATOR_DIR@>
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<!ENTITY userenvgeneratordir @USER_ENV_GENERATOR_DIR@>
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<!ENTITY CERTIFICATE_ROOT @CERTIFICATE_ROOT@>
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<!ENTITY FALLBACK_HOSTNAME @FALLBACK_HOSTNAME@>
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<!ENTITY MEMORY_ACCOUNTING_DEFAULT @MEMORY_ACCOUNTING_DEFAULT_YES_NO@>
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<!ENTITY KILL_USER_PROCESSES @KILL_USER_PROCESSES_YES_NO@>
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<!ENTITY DEBUGTTY @DEBUGTTY@>
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@ -0,0 +1,236 @@
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<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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<!ENTITY % entities SYSTEM "custom-entities.ent" >
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%entities;
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]>
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="org.freedesktop.hostname1" conditional='ENABLE_HOSTNAMED'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>org.freedesktop.hostname1</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>org.freedesktop.hostname1</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>org.freedesktop.hostname1</refname>
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<refpurpose>The D-Bus interface of systemd-hostnamed</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Introduction</title>
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<para>
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<citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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is a system service that can be used to control the host name and related machine meta data from user
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programs. This page describes the hostname semantics and the D-Bus interface.</para>
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</refsect1>
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<refsect1>
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<title>The D-Bus API</title>
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<para>The service exposes the following interfaces on the bus:</para>
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<programlisting>
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$ gdbus introspect --system \
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--dest org.freedesktop.hostname1 \
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--object-path /org/freedesktop/hostname1
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node /org/freedesktop/hostname1 {
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interface org.freedesktop.hostname1 {
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methods:
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SetHostname(in s name,
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in b user_interaction);
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SetStaticHostname(in s name,
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in b user_interaction);
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SetPrettyHostname(in s name,
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in b user_interaction);
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SetIconName(in s name,
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in b user_interaction);
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SetChassis(in s name,
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in b user_interaction);
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signals:
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properties:
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readonly s Hostname = 'dhcp-192-168-47-11';
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readonly s StaticHostname = 'lennarts-computer';
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readonly s PrettyHostname = 'Lennart’s Computer';
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readonly s IconName = 'computer-laptop';
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readonly s Chassis = 'laptop';
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};
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interface org.freedesktop.DBus.Properties {
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};
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interface org.freedesktop.DBus.Introspectable {
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};
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interface org.freedesktop.DBus.Peer {
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};
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};
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</programlisting>
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<para>Whenever the hostname or other meta data is changed via the daemon,
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<function>PropertyChanged</function> signals are sent out to subscribed clients. Changing a hostname
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using this interface is authenticated via PolicyKit.</para>
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</refsect1>
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<refsect1>
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<title>Semantics</title>
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<para>The <emphasis>static (configured) host name</emphasis> is the one configured in
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<filename>/etc/hostname</filename>. It is chosen by the local user. It is not always in sync with the
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current hostname as returned by the
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<citerefentry project='man-pages'><refentrytitle>gethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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system call. If no host name is configured this property will be the empty string. Setting this property
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to the empty string will remove <filename>/etc/hostname</filename>. This hostname should be an
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internet-style hostname, 7-bit lowercase ASCII, no special chars/spaces.</para>
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<para>The <emphasis>transient (dynamic) host name</emphasis> is the one configured via the kernel's
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<citerefentry project='man-pages'><refentrytitle>sethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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It can be different from the static hostname in case DHCP or mDNS have been configured to change the name
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based on network information. <!-- FIXME: it's not DHCP that configures this... -->
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This property is never empty. If no hostname is set this will default to
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<literal>&FALLBACK_HOSTNAME;</literal> (configurable at compilation time). Setting this property to the
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empty string will reset the dynamic hostname to the static host name. If no static host name is
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configured the dynamic host name will be reset to <literal>&FALLBACK_HOSTNAME;</literal>. This hostname
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should be an internet-style hostname, 7-bit lowercase ASCII, no special chars/spaces.</para>
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<para>The <emphasis>pretty host name</emphasis> is a free-form UTF-8 host name for presentation to the
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user. User interfaces should ensure that the pretty hostname and the static hostname stay in sync.
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I.e. when the former is <literal>Lennart’s Computer</literal> the latter should be
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<literal>lennarts-computer</literal>. If no pretty host name is set this setting will be the empty
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string. Applications should then find a suitable fallback, such as the dynamic hostname.</para>
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<para>The <emphasis>icon name</emphasis> is a name following the XDG icon naming spec. If not set,
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information such as the chassis type (see below) is used to find a suitable fallback icon name
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(i.e. <literal>computer-laptop</literal> vs. <literal>computer-desktop</literal> is picked based on the
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chassis information). If no such data is available, returns the empty string. In that case an application
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should fall back to a replacement icon, for example <literal>computer</literal>. If this property is set
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to the empty string, this automatic fallback name selection is enabled again.</para>
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<para>The <emphasis>chassis type</emphasis> should be one of the following that are currently defined:
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<literal>desktop</literal>, <literal>laptop</literal>, <literal>server</literal>,
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<literal>tablet</literal>, <literal>handset</literal>, as well as the special chassis types
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<literal>vm</literal> and <literal>container</literal> for virtualized systems. Note that in most cases
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the chassis type will be determined automatically from DMI/SMBIOS/ACPI firmware information. Writing to
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this setting is hence useful only to override misdetected chassis types, or configure a chassis type if
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none could be auto-detected. Set this property to the empty string to reenable the automatic detection of
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the chassis type from firmware information.</para>
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<para>A client which wants to change the local host name for DHCP/mDNS should invoke
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<code>SetHostname("newname", false)</code> as soon as the name is available and afterwards reset it via
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<code>SetHostname("")</code>.</para>
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<para>Note that <filename>systemd-hostnamed</filename> starts only on request and terminates after a
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short idle period. This effectively means that <function>PropertyChanged</function> messages are not sent
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out for changes made directly on the files (as in: administrator edits the files with vi). This is
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actually intended behavior: manual configuration changes should require manual reloading of them.</para>
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<para>The transient (dynamic) hostname directly maps to the kernel hostname. This hostname should be
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assumed to be highly dynamic, and hence should be watched directly, without involving
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<function>PropertyChanged</function> messages from <filename>systemd-hostnamed</filename>. For that, open
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<filename>/proc/sys/kernel/hostname</filename> and
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<citerefentry project='man-pages'><refentrytitle>poll</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for <constant>SIGHUP</constant> which is triggered by the kernel every time the hostname changes. Again:
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this is special for the transient (dynamic) hostname, and does not apply to the configured (fixed)
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hostname.</para>
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<para>Applications may bypass the daemon to read the hostname data if notifications of host name changes
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are not necessary. Use
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<citerefentry project='man-pages'><refentrytitle>gethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<filename>/etc/hostname</filename> (possibly with per-distribution fallbacks), and
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<citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for that. For more information on these files and syscalls see the respective man pages.</para>
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<para>The user_interaction boolean parameters can be used to control whether PolicyKit should
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interactively ask the user for authentication credentials if it needs to.</para>
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<para>The PolicyKit action for <function>SetHostname()</function> is
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<interfacename>org.freedesktop.hostname1.set-hostname</interfacename>. For
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<function>SetStaticHostname()</function> and <function>SetPrettyHostname()</function> it is
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<interfacename>org.freedesktop.hostname1.set-static-hostname</interfacename>. For
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<function>SetIconName()</function> and <function>SetChassis()</function> it is
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<interfacename>org.freedesktop.hostname1.set-machine-info</interfacename>.</para>
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<para>Here are three examples how the pretty hostname and the icon name should be used:
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<itemizedlist>
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<listitem><para>When registering DNS-SD services: use the pretty host name in the service name, and
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pass the icon name in the TXT data, if there is an icon name. Browsing clients can then show the server
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icon on each service. Especially useful for WebDAV stuff. Similar for UPnP media
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sharing.</para></listitem>
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<listitem><para>Set the bluetooth name to the pretty host name.</para></listitem>
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<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>
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</itemizedlist></para>
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<para>To properly handle name lookups with changing local hostnames without having to edit
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<filename>/etc/hosts</filename> for them, we recommend using <filename>systemd-hostnamed</filename> in
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combination with <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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</para>
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<para>Here are some recommendations to follow when generating a static (internet) hostname from a pretty
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name:
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<itemizedlist>
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<listitem><para>Generate a single DNS label only, not an FQDN. That means no dots allowed. Strip them,
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or replace them by <literal>-</literal>.</para></listitem>
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<listitem><para>It's probably safer not to use any non-ASCII chars, even if DNS allows this in some way
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these days. In fact, restrict your charset to <literal>a-zA-Z0-9</literal> and <literal>-</literal>.
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Strip other chars, or try to replace them in some smart way with chars from this set, for example
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<literal>ä</literal> → <literal>ae</literal>, and use <literal>-</literal> as replacement for all kinds
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of punctuation chars or spaces.</para></listitem>
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<listitem><para>Try to avoid creating repeated <literal>-</literal>, as well as <literal>-</literal> as
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the first or last char.</para></listitem>
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<listitem><para>Limit the hostname to 63 chars, which is the length of a DNS label.</para></listitem>
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<listitem><para>If after stripping special chars the empty string is the result, you can pass this
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as-is to <filename>systemd-hostnamed</filename> in which case it will automatically make
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<literal>&FALLBACK_HOSTNAME;</literal> out of this.</para></listitem>
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<listitem><para>It probably is a good idea to replace uppercase by lowercase chars.</para></listitem>
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</itemizedlist></para>
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<para>Note that while <filename>systemd-hostnamed</filename> applies some checks to the hostname you pass
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they are much looser than the recommendations above. For example, <filename>systemd-hostnamed</filename>
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will also accept <literal>_</literal> in the hostname, but I'd recommend not using this to avoid clashes
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with DNS-SD service types. Also <filename>systemd-hostnamed</filename> allows longer hostnames, but
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because of the DNS label limitations, I'd recommend not making use of this.</para>
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<para>Here are a couple of example conversions:
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<itemizedlist>
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<listitem><para><literal>Lennart's PC</literal> → <literal>lennarts-pc</literal></para></listitem>
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<listitem><para><literal>Müllers Computer</literal> → <literal>muellers-computer</literal></para></listitem>
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<listitem><para><literal>Voran!</literal> → <literal>voran</literal></para></listitem>
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<listitem><para><literal>Es war einmal ein Männlein</literal> → <literal>es-war-einmal-ein-maennlein</literal></para></listitem>
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<listitem><para><literal>Jawoll. Ist doch wahr!</literal> → <literal>jawoll-ist-doch-wahr</literal></para></listitem>
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<listitem><para><literal>レナート</literal> → <literal>localhost</literal></para></listitem>
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<listitem><para><literal>...zack!!! zack!...</literal> → <literal>zack-zack</literal></para></listitem>
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</itemizedlist></para>
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<para>Oh, and of course, an already valid internet hostname label you enter and pass through this
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conversion should stay unmodified, so that users have direct control of it, if they want -- by simply
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ignoring the fact that the pretty hostname is pretty and just edit it as if it was the normal internet
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name.</para>
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</refsect1>
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<refsect1>
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<title>Versioning</title>
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<para>These D-Bus interfaces follow <ulink url="http://0pointer.de/blog/projects/versioning-dbus.html">
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the usual interface versioning guidelines</ulink>.</para>
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</refsect1>
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<refsect1>
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<title>See also</title>
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<para>David Zeuthen's original Fedora
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<ulink url="https://fedoraproject.org/wiki/Features/BetterHostname">Feature page about xdg-hostname</ulink></para>
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</refsect1>
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</refentry>
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@ -44,6 +44,7 @@ manpages = [
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['nss-mymachines', '8', ['libnss_mymachines.so.2'], 'ENABLE_NSS_MYMACHINES'],
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['nss-resolve', '8', ['libnss_resolve.so.2'], 'ENABLE_NSS_RESOLVE'],
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['nss-systemd', '8', ['libnss_systemd.so.2'], 'ENABLE_NSS_SYSTEMD'],
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['org.freedesktop.hostname1', '5', [], 'ENABLE_HOSTNAMED'],
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['org.freedesktop.import1', '5', [], 'ENABLE_IMPORTD'],
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['org.freedesktop.login1', '5', [], 'ENABLE_LOGIND'],
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['org.freedesktop.machine1', '5', [], 'ENABLE_MACHINED'],
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@ -18,7 +18,7 @@
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<refnamediv>
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<refname>systemd-hostnamed.service</refname>
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<refname>systemd-hostnamed</refname>
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<refpurpose>Host name bus mechanism</refpurpose>
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<refpurpose>Daemon to control system hostname from programs</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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@ -29,19 +29,35 @@
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-hostnamed</filename> is a system service
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that may be used as a mechanism to change the system's hostname.
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<filename>systemd-hostnamed</filename> is automatically activated
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on request and terminates itself when it is unused.</para>
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<para><filename>systemd-hostnamed.service</filename> is a system service that may be used to change the
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system's hostname and related machine meta data from user programs. It is automatically activated on
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request and terminates itself when unused.</para>
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<para>It currently offers access to five variables:
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<itemizedlist>
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<listitem><para>The current host name (Example: <literal>dhcp-192-168-47-11</literal>)</para>
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</listitem>
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<listitem><para>The static (configured) host name (Example:
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<literal>lennarts-computer</literal>)</para></listitem>
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<listitem><para>The pretty host name (Example: <literal>Lennart's Computer</literal>)</para>
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</listitem>
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<listitem><para>A suitable icon name for the local host (Example:
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<literal>computer-laptop</literal>)</para></listitem>
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<listitem><para>A chassis type (Example: <literal>tablet</literal>)</para>
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</listitem>
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</itemizedlist></para>
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<para>The tool
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<citerefentry><refentrytitle>hostnamectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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is a command line client to this service.</para>
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<para>See the <ulink
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url="https://www.freedesktop.org/wiki/Software/systemd/hostnamed">
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developer documentation</ulink> for information about the APIs
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<filename>systemd-hostnamed</filename> provides.</para>
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<para>See the
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<citerefentry><refentrytitle>org.freedesktop.hostname1</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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for a description of the D-Bus API.</para>
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</refsect1>
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<refsect1>
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