интерфейс D-Bus для systemd-host named (The D-Bus interface of systemd-hostnamed)
Имя (Name)
org.freedesktop.hostname1 - The D-Bus interface of
systemd-hostnamed
Вступление (Introduction)
systemd-hostnamed.service(8) 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.
API D-bus (системы межпроцессного взаимодействия) (The d-bus API)
The service exposes the following interfaces on the bus:
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);
Describe(out s json);
properties:
readonly s Hostname = '...';
readonly s StaticHostname = '...';
readonly s PrettyHostname = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly s DefaultHostname = '...';
readonly s HostnameSource = '...';
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 = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly s HardwareVendor = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly s HardwareModel = '...';
};
interface org.freedesktop.DBus.Peer { ... };
interface org.freedesktop.DBus.Introspectable { ... };
interface org.freedesktop.DBus.Properties { ... };
};
Whenever the hostname or other metadata is changed via the
daemon, PropertyChanged signals are sent out to subscribed
clients. Changing a hostname using this interface is
authenticated via polkit
SEMANTICS
The StaticHostname property exposes the "static" hostname
configured in /etc/hostname. It is not always in sync with the
current hostname as returned by the gethostname(3) system call.
If no static hostname is configured this property will be the
empty string.
When systemd(1) or systemd-hostnamed.service(8) set the hostname,
this static hostname has the highest priority.
The Hostname property exposes the actual hostname configured in
the kernel via sethostname(3). It can be different from the
static hostname. This property is never empty.
The PrettyHostname property exposes the pretty hostname which 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. E.g. when the former is "Lennart's
Computer" the latter should be "lennarts-computer". 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.
The DefaultHostname property exposes the default hostname
(configured through os-release(5), or a fallback set at
compilation time).
The HostnameSource property exposes the origin of the currently
configured hostname. One of "static" (set from /etc/hostname),
"transient" (a non-permanent hostname from an external source),
"default" (the value from os-release or the compiled-in
fallback).
The IconName property exposes the icon 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. "computer-laptop" vs. "computer-desktop" 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 "computer". If this
property is set to the empty string, the automatic fallback name
selection is enabled again.
The Chassis property exposes a chassis type, one of the currently
defined chassis types: "desktop", "laptop", "server", "tablet",
"handset", as well as the special chassis types "vm" and
"container" 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.
Note that systemd-hostnamed starts only on request and terminates
after a short idle period. This effectively means that
PropertyChanged 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.
The transient (dynamic) hostname exposed by the Hostname property
maps directly to the kernel hostname. This hostname should be
assumed to be highly dynamic, and hence should be watched
directly, without depending on PropertyChanged messages from
systemd-hostnamed. To accomplish this, open
/proc/sys/kernel/hostname and poll(3) for SIGHUP 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.
Applications may read the hostname data directly if hostname
change notifications are not necessary. Use gethostname(3),
/etc/hostname (possibly with per-distribution fallbacks), and
machine-info(3) for that. For more information on these files and
syscalls see the respective man pages.
KernelName, KernelRelease, and KernelVersion expose the kernel
name (e.g. "Linux"), release (e.g. "5.0.0-11"), and version
(i.e. the build number, e.g. "#11") as reported by uname(2).
OperatingSystemPrettyName, OperatingSystemCPEName, and HomeURL
expose the PRETTY_NAME=, CPE_NAME= and HOME_URL= fields from
os-release(5). The purpose of those properties is to allow remote
clients to access this information over D-Bus. Local clients can
access the information directly.
Methods
SetHostname() sets the transient (dynamic) hostname, which is
used if no static hostname is set. This value must be an
internet-style hostname, 7-bit lowercase ASCII, no special
chars/spaces. An empty string will unset the transient hostname.
SetStaticHostname() sets the static hostname which is exposed by
the StaticHostname property. When called with an empty argument,
the static configuration in /etc/hostname is removed. Since the
static hostname has the highest priority, calling this function
usually affects also the Hostname property and the effective
hostname configured in the kernel.
SetPrettyHostname() sets the pretty hostname which is exposed by
the PrettyHostname property.
SetIconName(), SetChassis(), SetDeployment(), and SetLocation()
set the properties IconName (the name of the icon representing
for the machine), Chassis (the machine form factor), Deployment
(the system deployment environment), and Location (physical
system location), respectively.
PrettyHostname, IconName, Chassis, Deployment, and Location are
stored in /etc/machine-info. See machine-info(5) for the
semantics of those settings.
GetProductUUID() returns the "product UUID" as exposed by the
kernel based on DMI information in
/sys/class/dmi/id/product_uuid. Reading the file directly
requires root privileges, and this method allows access to
unprivileged clients through the polkit framework.
Describe() returns a JSON representation of all properties in
one.
Security
The interactive boolean parameters can be used to control whether
polkit should interactively ask the user for authentication
credentials if required.
The polkit action for SetHostname() is
org.freedesktop.hostname1.set-hostname. For SetStaticHostname()
and SetPrettyHostname() it is
org.freedesktop.hostname1.set-static-hostname. For SetIconName(),
SetChassis(), SetDeployment() and SetLocation() it is
org.freedesktop.hostname1.set-machine-info.
RECOMMENDATIONS
Here are three examples that show how the pretty hostname and the
icon name should be used:
• 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.
• Set the bluetooth name to the pretty hostname.
• 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.
To properly handle name lookups with changing local hostnames
without having to edit /etc/hosts, we recommend using
systemd-hostnamed in combination with nss-myhostname(3).
Here are some recommendations to follow when generating a static
(internet) hostname from a pretty name:
• Generate a single DNS label only, not an FQDN. That means no
dots allowed. Strip them, or replace them with "-".
• 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 "a-zA-Z0-9" and "-". Strip other chars, or
try to replace them in some smart way with chars from this
set, for example "ä" → "ae", and use "-" as the replacement
for all punctuation characters and whitespace.
• Try to avoid creating repeated "-", as well as "-" as the
first or last char.
• Limit the hostname to 63 chars, which is the length of a DNS
label.
• If after stripping special chars the empty string is the
result, you can pass this as-is to systemd-hostnamed in which
case it will automatically use a suitable fallback.
• Uppercase charaacters should be replaced with their lowercase
equivalents.
Note that while systemd-hostnamed applies some checks to the
hostname you pass they are much looser than the recommendations
above. For example, systemd-hostnamed will also accept "_" in the
hostname, but we recommend not using this to avoid clashes with
DNS-SD service types. Also systemd-hostnamed allows longer
hostnames, but because of the DNS label limitations, we recommend
not making use of this.
Here are a couple of example conversions:
• "Lennart's PC" → "lennarts-pc"
• "Müllers Computer" → "muellers-computer"
• "Voran!" → "voran"
• "Es war einmal ein Männlein" → "es-war-einmal-ein-maennlein"
• "Jawoll. Ist doch wahr!" → "jawoll-ist-doch-wahr"
• "レナート" → "localhost"
• "...zack!!! zack!..." → "zack-zack"
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.
Версии (Versions)
These D-Bus interfaces follow the usual interface versioning
guidelines
Примеры (Examples)
Example 1. Introspect org.freedesktop.hostname1 on the bus
$ gdbus introspect --system \
--dest org.freedesktop.hostname1 \
--object-path /org/freedesktop/hostname1
Смотри также (See also)
David Zeuthen's original Fedora Feature page about
xdg-hostname
Примечание (Note)
1. polkit
https://www.freedesktop.org/software/polkit/docs/latest/
2. the usual interface versioning guidelines
http://0pointer.de/blog/projects/versioning-dbus.html
3. Feature page about xdg-hostname
https://fedoraproject.org/wiki/Features/BetterHostname
