ORG.FREEDESKTOP.HOSTNAME1(5org.freedesktop.hostnamORG.FREEDESKTOP.HOSTNAME1(5)
NAME
org.freedesktop.hostname1 - The D-Bus interface of systemd-hostnamed
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.
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);
GetHardwareSerial(out s serial);
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 = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly s FirmwareVersion = '...';
};
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[1].
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(2). 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(2), /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.
VERSIONING
These D-Bus interfaces follow the usual interface versioning
guidelines[2].
EXAMPLES
Example 1. Introspect org.freedesktop.hostname1 on the bus
$ gdbus introspect --system \
--dest org.freedesktop.hostname1 \
--object-path /org/freedesktop/hostname1
SEE ALSO
David Zeuthen's original Fedora Feature page about xdg-hostname[3]
NOTES
1. polkit
https://www.freedesktop.org/software/polkit/docs/latest/
2. the usual interface versioning guidelines
https://0pointer.de/blog/projects/versioning-dbus.html
3. Feature page about xdg-hostname
https://fedoraproject.org/wiki/Features/BetterHostname
systemd 252 ORG.FREEDESKTOP.HOSTNAME1(5)
Generated by dwww version 1.15 on Wed Jun 26 01:01:38 CEST 2024.