1<?xml version="1.0"?> 2<!--*-nxml-*--> 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" > 6%entities; 7]> 8<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> 9 10<refentry id="org.freedesktop.hostname1" conditional='ENABLE_HOSTNAMED' 11 xmlns:xi="http://www.w3.org/2001/XInclude"> 12 <refentryinfo> 13 <title>org.freedesktop.hostname1</title> 14 <productname>systemd</productname> 15 </refentryinfo> 16 17 <refmeta> 18 <refentrytitle>org.freedesktop.hostname1</refentrytitle> 19 <manvolnum>5</manvolnum> 20 </refmeta> 21 22 <refnamediv> 23 <refname>org.freedesktop.hostname1</refname> 24 <refpurpose>The D-Bus interface of systemd-hostnamed</refpurpose> 25 </refnamediv> 26 27 <refsect1> 28 <title>Introduction</title> 29 30 <para> 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> 34 </refsect1> 35 36 <refsect1> 37 <title>The D-Bus API</title> 38 39 <para>The service exposes the following interfaces on the bus:</para> 40 41 <programlisting executable="systemd-hostnamed" node="/org/freedesktop/hostname1" interface="org.freedesktop.hostname1"> 42node /org/freedesktop/hostname1 { 43 interface org.freedesktop.hostname1 { 44 methods: 45 SetHostname(in s hostname, 46 in b interactive); 47 SetStaticHostname(in s hostname, 48 in b interactive); 49 SetPrettyHostname(in s hostname, 50 in b interactive); 51 SetIconName(in s icon, 52 in b interactive); 53 SetChassis(in s chassis, 54 in b interactive); 55 SetDeployment(in s deployment, 56 in b interactive); 57 SetLocation(in s location, 58 in b interactive); 59 GetProductUUID(in b interactive, 60 out ay uuid); 61 GetHardwareSerial(out s serial); 62 Describe(out s json); 63 properties: 64 readonly s Hostname = '...'; 65 readonly s StaticHostname = '...'; 66 readonly s PrettyHostname = '...'; 67 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 68 readonly s DefaultHostname = '...'; 69 readonly s HostnameSource = '...'; 70 readonly s IconName = '...'; 71 readonly s Chassis = '...'; 72 readonly s Deployment = '...'; 73 readonly s Location = '...'; 74 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 75 readonly s KernelName = '...'; 76 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 77 readonly s KernelRelease = '...'; 78 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 79 readonly s KernelVersion = '...'; 80 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 81 readonly s OperatingSystemPrettyName = '...'; 82 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 83 readonly s OperatingSystemCPEName = '...'; 84 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 85 readonly s HomeURL = '...'; 86 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 87 readonly s HardwareVendor = '...'; 88 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 89 readonly s HardwareModel = '...'; 90 @org.freedesktop.DBus.Property.EmitsChangedSignal("const") 91 readonly s FirmwareVersion = '...'; 92 }; 93 interface org.freedesktop.DBus.Peer { ... }; 94 interface org.freedesktop.DBus.Introspectable { ... }; 95 interface org.freedesktop.DBus.Properties { ... }; 96}; 97 </programlisting> 98 99 <!--method GetHardwareSerial is not documented!--> 100 101 <!--property HardwareVendor is not documented!--> 102 103 <!--property HardwareModel is not documented!--> 104 105 <!--property FirmwareVersion is not documented!--> 106 107 <!--Autogenerated cross-references for systemd.directives, do not edit--> 108 109 <variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.hostname1"/> 110 111 <variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.hostname1"/> 112 113 <variablelist class="dbus-method" generated="True" extra-ref="SetHostname()"/> 114 115 <variablelist class="dbus-method" generated="True" extra-ref="SetStaticHostname()"/> 116 117 <variablelist class="dbus-method" generated="True" extra-ref="SetPrettyHostname()"/> 118 119 <variablelist class="dbus-method" generated="True" extra-ref="SetIconName()"/> 120 121 <variablelist class="dbus-method" generated="True" extra-ref="SetChassis()"/> 122 123 <variablelist class="dbus-method" generated="True" extra-ref="SetDeployment()"/> 124 125 <variablelist class="dbus-method" generated="True" extra-ref="SetLocation()"/> 126 127 <variablelist class="dbus-method" generated="True" extra-ref="GetProductUUID()"/> 128 129 <variablelist class="dbus-method" generated="True" extra-ref="GetHardwareSerial()"/> 130 131 <variablelist class="dbus-method" generated="True" extra-ref="Describe()"/> 132 133 <variablelist class="dbus-property" generated="True" extra-ref="Hostname"/> 134 135 <variablelist class="dbus-property" generated="True" extra-ref="StaticHostname"/> 136 137 <variablelist class="dbus-property" generated="True" extra-ref="PrettyHostname"/> 138 139 <variablelist class="dbus-property" generated="True" extra-ref="DefaultHostname"/> 140 141 <variablelist class="dbus-property" generated="True" extra-ref="HostnameSource"/> 142 143 <variablelist class="dbus-property" generated="True" extra-ref="IconName"/> 144 145 <variablelist class="dbus-property" generated="True" extra-ref="Chassis"/> 146 147 <variablelist class="dbus-property" generated="True" extra-ref="Deployment"/> 148 149 <variablelist class="dbus-property" generated="True" extra-ref="Location"/> 150 151 <variablelist class="dbus-property" generated="True" extra-ref="KernelName"/> 152 153 <variablelist class="dbus-property" generated="True" extra-ref="KernelRelease"/> 154 155 <variablelist class="dbus-property" generated="True" extra-ref="KernelVersion"/> 156 157 <variablelist class="dbus-property" generated="True" extra-ref="OperatingSystemPrettyName"/> 158 159 <variablelist class="dbus-property" generated="True" extra-ref="OperatingSystemCPEName"/> 160 161 <variablelist class="dbus-property" generated="True" extra-ref="HomeURL"/> 162 163 <variablelist class="dbus-property" generated="True" extra-ref="HardwareVendor"/> 164 165 <variablelist class="dbus-property" generated="True" extra-ref="HardwareModel"/> 166 167 <variablelist class="dbus-property" generated="True" extra-ref="FirmwareVersion"/> 168 169 <!--End of Autogenerated section--> 170 171 <para>Whenever the hostname or other metadata is changed via the daemon, 172 <function>PropertyChanged</function> signals are sent out to subscribed clients. Changing a hostname 173 using this interface is authenticated via 174 <ulink url="https://www.freedesktop.org/software/polkit/docs/latest/">polkit</ulink>.</para> 175 </refsect1> 176 177 <refsect1> 178 <title>Semantics</title> 179 180 <para>The <varname>StaticHostname</varname> property exposes the "static" hostname configured in 181 <filename>/etc/hostname</filename>. It is not always in sync with the current hostname as returned by the 182 <citerefentry project="man-pages"><refentrytitle>gethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry> 183 system call. If no static hostname is configured this property will be the empty string.</para> 184 185 <para>When <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> or 186 <citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> 187 set the hostname, this static hostname <emphasis>has the highest priority</emphasis>.</para> 188 189 <para>The <varname>Hostname</varname> property exposes the actual hostname configured in the kernel via 190 <citerefentry project="man-pages"><refentrytitle>sethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>. 191 It can be different from the static hostname. This property is never empty.</para> 192 193 <para>The <varname>PrettyHostname</varname> property exposes the <emphasis>pretty hostname</emphasis> 194 which is a free-form UTF-8 hostname for presentation to the user. User interfaces should ensure that the 195 pretty hostname and the static hostname stay in sync. E.g. when the former is <literal>Lennart’s 196 Computer</literal> the latter should be <literal>lennarts-computer</literal>. If no pretty hostname is 197 set this setting will be the empty string. Applications should then find a suitable fallback, such as the 198 dynamic hostname.</para> 199 200 <para>The <varname>DefaultHostname</varname> property exposes the default hostname (configured through 201 <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>, or a 202 fallback set at compilation time).</para> 203 204 <para>The <varname>HostnameSource</varname> property exposes the origin of the currently configured 205 hostname. One of <literal>static</literal> (set from <filename>/etc/hostname</filename>), 206 <literal>transient</literal> (a non-permanent hostname from an external source), 207 <literal>default</literal> (the value from <filename>os-release</filename> or the compiled-in 208 fallback).</para> 209 210 <para>The <varname>IconName</varname> property exposes the <emphasis>icon name</emphasis> following the 211 XDG icon naming spec. If not set, information such as the chassis type (see below) is used to find a 212 suitable fallback icon name (i.e. <literal>computer-laptop</literal> 213 vs. <literal>computer-desktop</literal> is picked based on the chassis information). If no such data is 214 available, the empty string is returned. In that case an application should fall back to a replacement 215 icon, for example <literal>computer</literal>. If this property is set to the empty string, the automatic 216 fallback name selection is enabled again.</para> 217 218 <para>The <varname>Chassis</varname> property exposes a <emphasis>chassis type</emphasis>, one of the 219 currently defined chassis types: <literal>desktop</literal>, <literal>laptop</literal>, 220 <literal>server</literal>, <literal>tablet</literal>, <literal>handset</literal>, as well as the special 221 chassis types <literal>vm</literal> and <literal>container</literal> for virtualized systems. Note that 222 in most cases the chassis type will be determined automatically from DMI/SMBIOS/ACPI firmware 223 information. Writing to this setting is hence useful only to override misdetected chassis types, or to 224 configure the chassis type if it could not be auto-detected. Set this property to the empty string to 225 reenable the automatic detection of the chassis type from firmware information.</para> 226 227 <para>Note that <filename>systemd-hostnamed</filename> starts only on request and terminates after a 228 short idle period. This effectively means that <function>PropertyChanged</function> messages are not sent 229 out for changes made directly on the files (as in: administrator edits the files with vi). This is 230 the intended behavior: manual configuration changes should require manual reloading.</para> 231 232 <para>The transient (dynamic) hostname exposed by the <varname>Hostname</varname> property maps directly 233 to the kernel hostname. This hostname should be assumed to be highly dynamic, and hence should be watched 234 directly, without depending on <function>PropertyChanged</function> messages from 235 <filename>systemd-hostnamed</filename>. To accomplish this, open 236 <filename>/proc/sys/kernel/hostname</filename> and 237 <citerefentry project="man-pages"><refentrytitle>poll</refentrytitle><manvolnum>3</manvolnum></citerefentry> 238 for <constant>SIGHUP</constant> which is triggered by the kernel every time the hostname changes. Again: 239 this is special for the transient (dynamic) hostname, and does not apply to the configured (fixed) 240 hostname.</para> 241 242 <para>Applications may read the hostname data directly if hostname change notifications 243 are not necessary. Use 244 <citerefentry project="man-pages"><refentrytitle>gethostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 245 <filename>/etc/hostname</filename> (possibly with per-distribution fallbacks), and 246 <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>3</manvolnum></citerefentry> 247 for that. For more information on these files and syscalls see the respective man pages.</para> 248 249 <para><varname>KernelName</varname>, <varname>KernelRelease</varname>, and 250 <varname>KernelVersion</varname> expose the kernel name (e.g. <literal>Linux</literal>), release 251 (e.g. <literal>5.0.0-11</literal>), and version (i.e. the build number, e.g. <literal>#11</literal>) as 252 reported by <citerefentry project="man-pages"><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>. 253 <varname>OperatingSystemPrettyName</varname>, <varname>OperatingSystemCPEName</varname>, and 254 <varname>HomeURL</varname> expose the <varname>PRETTY_NAME=</varname>, <varname>CPE_NAME=</varname> and 255 <varname>HOME_URL=</varname> fields from 256 <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The 257 purpose of those properties is to allow remote clients to access this information over D-Bus. Local 258 clients can access the information directly.</para> 259 260 <refsect2> 261 <title>Methods</title> 262 263 <para><function>SetHostname()</function> sets the transient (dynamic) hostname, which is used if no 264 static hostname is set. This value must be an internet-style hostname, 7-bit lowercase ASCII, no 265 special chars/spaces. An empty string will unset the transient hostname.</para> 266 267 <para><function>SetStaticHostname()</function> sets the static hostname which is exposed by the 268 <varname>StaticHostname</varname> property. When called with an empty argument, the static 269 configuration in <filename>/etc/hostname</filename> is removed. Since the static hostname has the 270 highest priority, calling this function usually affects also the <varname>Hostname</varname> property 271 and the effective hostname configured in the kernel.</para> 272 273 <para><function>SetPrettyHostname()</function> sets the pretty hostname which is exposed by the 274 <varname>PrettyHostname</varname> property.</para> 275 276 <para><function>SetIconName()</function>, <function>SetChassis()</function>, 277 <function>SetDeployment()</function>, and <function>SetLocation()</function> set the properties 278 <varname>IconName</varname> (the name of the icon representing for the machine), 279 <varname>Chassis</varname> (the machine form factor), <varname>Deployment</varname> (the system 280 deployment environment), and <varname>Location</varname> (physical system location), respectively. 281 </para> 282 283 <para><varname>PrettyHostname</varname>, <varname>IconName</varname>, <varname>Chassis</varname>, 284 <varname>Deployment</varname>, and <varname>Location</varname> are stored in 285 <filename>/etc/machine-info</filename>. See 286 <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry> for 287 the semantics of those settings.</para> 288 289 <para><function>GetProductUUID()</function> returns the "product UUID" as exposed by the kernel based 290 on DMI information in <filename>/sys/class/dmi/id/product_uuid</filename>. Reading the file directly 291 requires root privileges, and this method allows access to unprivileged clients through the polkit 292 framework.</para> 293 294 <para><function>Describe()</function> returns a JSON representation of all properties in one.</para> 295 </refsect2> 296 297 <refsect2> 298 <title>Security</title> 299 300 <para>The <varname>interactive</varname> boolean parameters can be used to control whether polkit 301 should interactively ask the user for authentication credentials if required.</para> 302 303 <para>The polkit action for <function>SetHostname()</function> is 304 <interfacename>org.freedesktop.hostname1.set-hostname</interfacename>. For 305 <function>SetStaticHostname()</function> and <function>SetPrettyHostname()</function> it is 306 <interfacename>org.freedesktop.hostname1.set-static-hostname</interfacename>. For 307 <function>SetIconName()</function>, <function>SetChassis()</function>, <function>SetDeployment()</function> 308 and <function>SetLocation()</function> it is 309 <interfacename>org.freedesktop.hostname1.set-machine-info</interfacename>.</para> 310 </refsect2> 311 </refsect1> 312 313 <refsect1> 314 <title>Recommendations</title> 315 316 <para>Here are three examples that show how the pretty hostname and the icon name should be used: 317 <itemizedlist> 318 <listitem><para>When registering DNS-SD services: use the pretty hostname in the service name, and pass 319 the icon name in the TXT data, if there is an icon name. Browsing clients can then show the server icon 320 on each service. This is especially useful for WebDAV applications or UPnP media sharing. 321 </para></listitem> 322 323 <listitem><para>Set the bluetooth name to the pretty hostname.</para></listitem> 324 325 <listitem><para>When your file browser has a "Computer" icon, replace the name with the pretty hostname 326 if set, and the icon with the icon name, if it is set.</para></listitem> 327 </itemizedlist></para> 328 329 <para>To properly handle name lookups with changing local hostnames without having to edit 330 <filename>/etc/hosts</filename>, we recommend using <filename>systemd-hostnamed</filename> in combination 331 with <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>. 332 </para> 333 334 <para>Here are some recommendations to follow when generating a static (internet) hostname from a pretty 335 name: 336 <itemizedlist> 337 <listitem><para>Generate a single DNS label only, not an FQDN. That means no dots allowed. Strip them, 338 or replace them with <literal>-</literal>.</para></listitem> 339 340 <listitem><para>It's probably safer to not use any non-ASCII chars, even if DNS allows this in some way 341 these days. In fact, restrict your charset to <literal>a-zA-Z0-9</literal> and <literal>-</literal>. 342 Strip other chars, or try to replace them in some smart way with chars from this set, for example 343 <literal>ä</literal> → <literal>ae</literal>, and use <literal>-</literal> as the replacement for all 344 punctuation characters and whitespace.</para></listitem> 345 346 <listitem><para>Try to avoid creating repeated <literal>-</literal>, as well as <literal>-</literal> as 347 the first or last char.</para></listitem> 348 349 <listitem><para>Limit the hostname to 63 chars, which is the length of a DNS label.</para></listitem> 350 351 <listitem><para>If after stripping special chars the empty string is the result, you can pass this 352 as-is to <filename>systemd-hostnamed</filename> in which case it will automatically use a suitable 353 fallback.</para></listitem> 354 355 <listitem><para>Uppercase charaacters should be replaced with their lowercase equivalents. 356 </para></listitem> 357 </itemizedlist></para> 358 359 <para>Note that while <filename>systemd-hostnamed</filename> applies some checks to the hostname you pass 360 they are much looser than the recommendations above. For example, <filename>systemd-hostnamed</filename> 361 will also accept <literal>_</literal> in the hostname, but we recommend not using this to avoid clashes 362 with DNS-SD service types. Also <filename>systemd-hostnamed</filename> allows longer hostnames, but 363 because of the DNS label limitations, we recommend not making use of this.</para> 364 365 <para>Here are a couple of example conversions: 366 <itemizedlist> 367 <listitem><para><literal>Lennart's PC</literal> → <literal>lennarts-pc</literal></para></listitem> 368 <listitem><para><literal>Müllers Computer</literal> → <literal>muellers-computer</literal></para></listitem> 369 <listitem><para><literal>Voran!</literal> → <literal>voran</literal></para></listitem> 370 <listitem><para><literal>Es war einmal ein Männlein</literal> → <literal>es-war-einmal-ein-maennlein</literal></para></listitem> 371 <listitem><para><literal>Jawoll. Ist doch wahr!</literal> → <literal>jawoll-ist-doch-wahr</literal></para></listitem> 372 <listitem><para><literal>レナート</literal> → <literal>localhost</literal></para></listitem> 373 <listitem><para><literal>...zack!!! zack!...</literal> → <literal>zack-zack</literal></para></listitem> 374 </itemizedlist></para> 375 376 <para>Of course, an already valid internet hostname label you enter and pass through this 377 conversion should stay unmodified, so that users have direct control of it, if they want — by simply 378 ignoring the fact that the pretty hostname is pretty and just edit it as if it was the normal internet 379 name.</para> 380 </refsect1> 381 382 <xi:include href="org.freedesktop.locale1.xml" xpointer="versioning"/> 383 384 <refsect1> 385 <title>Examples</title> 386 387 <example> 388 <title>Introspect <interfacename>org.freedesktop.hostname1</interfacename> on the bus</title> 389 390 <programlisting>$ gdbus introspect --system \ 391 --dest org.freedesktop.hostname1 \ 392 --object-path /org/freedesktop/hostname1 393 </programlisting> 394 </example> 395 </refsect1> 396 397 <refsect1> 398 <title>See also</title> 399 400 <para>David Zeuthen's original Fedora 401 <ulink url="https://fedoraproject.org/wiki/Features/BetterHostname">Feature page about xdg-hostname</ulink></para> 402 </refsect1> 403</refentry> 404