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man: various tweaks to org.freedesktop.hostname1(5)

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Co-Authored-By: Daan De Meyer <daan.j.demeyer@gmail.com>
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2020-04-11 17:08:04 +02:00
parent 4fb222c4b2
commit 8024ac43b9
1 changed files with 42 additions and 41 deletions
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man/org.freedesktop.hostname1.xml
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@ -29,7 +29,7 @@
<para>
<citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
is a system service that can be used to control the host name and related machine meta data from user
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>
@ -121,7 +121,7 @@ node /org/freedesktop/hostname1 {
<!--property HomeURL is not documented!-->
<para>Whenever the hostname or other meta data is changed via the daemon,
<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 PolicyKit.</para>
</refsect1>
@ -129,73 +129,73 @@ node /org/freedesktop/hostname1 {
<refsect1>
<title>Semantics</title>
<para>The <emphasis>static (configured) host name</emphasis> is the one configured in
<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 host name is configured this property will be the empty string. Setting this property
to the empty string will remove <filename>/etc/hostname</filename>. This hostname should be an
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) host name</emphasis> is the one configured via the kernel's
<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 in case DHCP or mDNS have been configured to change the name
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 host name. If no static host name is
configured the dynamic host name will be reset to <literal>&FALLBACK_HOSTNAME;</literal>. This hostname
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 host name</emphasis> is a free-form UTF-8 host name for presentation to the
<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 host name is set this setting will be the empty
<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, returns the empty string. In that case an application
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, this automatic fallback name selection is enabled again.</para>
to the empty string, the automatic fallback name selection is enabled again.</para>
<para>The <emphasis>chassis type</emphasis> should be one of the following that are currently defined:
<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 configure a chassis type if
none could be auto-detected. Set this property to the empty string to reenable the automatic detection of
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>A client which wants to change the local host name for DHCP/mDNS should invoke
<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>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
actually intended behavior: manual configuration changes should require manual reloading of them.</para>
the intended behavior: manual configuration changes should require manual reloading.</para>
<para>The transient (dynamic) hostname directly maps to the kernel hostname. This hostname should be
assumed to be highly dynamic, and hence should be watched directly, without involving
<function>PropertyChanged</function> messages from <filename>systemd-hostnamed</filename>. For that, open
<filename>/proc/sys/kernel/hostname</filename> and
<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 bypass the daemon to read the hostname data if notifications of host name changes
<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>
<para>The user_interaction boolean parameters can be used to control whether PolicyKit should
interactively ask the user for authentication credentials if it needs to.</para>
<para>The <varname>user_interaction</varname> boolean parameters can be used to control whether PolicyKit
should interactively ask the user for authentication credentials if required.</para>
<para>The PolicyKit action for <function>SetHostname()</function> is
<interfacename>org.freedesktop.hostname1.set-hostname</interfacename>. For
@ -204,20 +204,20 @@ node /org/freedesktop/hostname1 {
<function>SetIconName()</function> and <function>SetChassis()</function> it is
<interfacename>org.freedesktop.hostname1.set-machine-info</interfacename>.</para>
<para>Here are three examples how the pretty hostname and the icon name should be used:
<para>Here are three examples show how the pretty hostname and the icon name should be used:
<itemizedlist>
<listitem><para>When registering DNS-SD services: use the pretty host name in the service name, and
<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. Especially useful for WebDAV stuff. Similar for UPnP media
sharing.</para></listitem>
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 host name.</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> for them, we recommend using <filename>systemd-hostnamed</filename> in
<filename>/etc/hosts</filename>, we recommend using <filename>systemd-hostnamed</filename> in
combination with <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
@ -225,13 +225,13 @@ node /org/freedesktop/hostname1 {
name:
<itemizedlist>
<listitem><para>Generate a single DNS label only, not an FQDN. That means no dots allowed. Strip them,
or replace them by <literal>-</literal>.</para></listitem>
or replace them with <literal>-</literal>.</para></listitem>
<listitem><para>It's probably safer not to use any non-ASCII chars, even if DNS allows this in some way
<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 replacement for all kinds
of punctuation chars or spaces.</para></listitem>
<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>
@ -239,17 +239,18 @@ node /org/freedesktop/hostname1 {
<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 make
<literal>&FALLBACK_HOSTNAME;</literal> out of this.</para></listitem>
as-is to <filename>systemd-hostnamed</filename> in which case it will automatically use
<literal>&FALLBACK_HOSTNAME;</literal>.</para></listitem>
<listitem><para>It probably is a good idea to replace uppercase by lowercase chars.</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 I'd recommend not using this to avoid clashes
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, I'd recommend not making use of this.</para>
because of the DNS label limitations, we recommend not making use of this.</para>
<para>Here are a couple of example conversions:
<itemizedlist>
@ -262,7 +263,7 @@ node /org/freedesktop/hostname1 {
<listitem><para><literal>...zack!!! zack!...</literal> → <literal>zack-zack</literal></para></listitem>
</itemizedlist></para>
<para>Oh, and of course, an already valid internet hostname label you enter and pass through this
<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>