org.freedesktop.hostname1 - The D-Bus interface of systemd-hostnamed
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 service exposes the following interfaces on the bus:
.RS 4
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 t OperatingSystemSupportEnd = ...;
@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 = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly s FirmwareVendor = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly t FirmwareDate = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly ay MachineID = [...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly ay BootID = [...];
};
interface org.freedesktop.DBus.Peer { ... };
interface org.freedesktop.DBus.Introspectable { ... };
interface org.freedesktop.DBus.Properties { ... };
};
.RE
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].
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.
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.
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.
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 "-".
·
Its 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 characters 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:
·
"Lennarts 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.
These D-Bus interfaces follow the usual interface versioning guidelines[2].
Example 1. Introspect org.freedesktop.hostname1 on the bus
.RS 4
$ gdbus introspect --system \
--dest org.freedesktop.hostname1 \
--object-path /org/freedesktop/hostname1
.RE
David Zeuthens original Fedora Feature page about xdg-hostname[3]
FirmwareVersion and GetHardwareSerial()
were added in version 251.
OperatingSystemSupportEnd, FirmwareVendor, and
FirmwareDate were added in version 253.
MachineID, and BootID were added in version
256.
polkit
the usual interface versioning guidelines
Feature page about xdg-hostname