org.freedesktop.hostname1(5)

.SH "NAME" org.freedesktop.hostname1 - The D-Bus interface of systemd-hostnamed

.SH "INTRODUCTION"

.PP 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.

.SH "THE D-BUS API"

.PP 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);


      SetTags(in  as tags);


      AddAndRemoveTags(in  as add,


                       in  as remove);


      GetProductUUID(in  b interactive,


                     out ay uuid);


      GetHardwareSerial(out s serial);


      Describe(out s json);


      GetMachineInfo(in  s field,


                     out s value);


    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 = '...';


      readonly as Tags = ['...', ...];


      @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 OperatingSystemFancyName = '...';


      @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 OperatingSystemImageID = '...';


      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")


      readonly s OperatingSystemImageVersion = '...';


      @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 HardwareSKU = '...';


      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")


      readonly s HardwareVersion = '...';


      @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 = [...];


      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")


      readonly u VSockCID = ...;


      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")


      readonly s ChassisAssetTag = '...';


  };


  interface org.freedesktop.DBus.Peer { ... };


  interface org.freedesktop.DBus.Introspectable { ... };


  interface org.freedesktop.DBus.Properties { ... };
};

.PP 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].

.SH "SEMANTICS"

.PP 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.

.PP When systemd(1) or systemd-hostnamed.service(8) set the hostname, this static hostname has the highest priority.

.PP 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.

.PP 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.

.PP The DefaultHostname property exposes the default hostname (configured through os-release(5), or a fallback set at compilation time).

.PP 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).

.PP 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.

.PP 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.

.PP The Tags property exposes a list of machine tags: short labels that may be used to classify and group machines for management purposes, for example to identify the role a machine plays in a deployment, the fleet or organizational unit it belongs to, or any other administrator-defined attribute. Each individual tag is 1...255 characters long and consists only of the ASCII alphanumeric characters, - and .. The tags are stored as a colon-separated list in the TAGS= field of /etc/machine-info, see machine-info(5) for details. If no tags are configured this property is the empty list.

.PP 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.

.PP 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.

.PP 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(5) for that. For more information on these files and syscalls see the respective man pages.

.PP 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).

.PP OperatingSystemPrettyName, OperatingSystemFancyName, OperatingSystemCPEName, and HomeURL expose the PRETTY_NAME=, FANCY_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.

.PP MachineID expose the 128bit machine ID, see machine-id(5) for details.

.PP BootID expose the 128bit boot ID, as per /proc/sys/kernel/random/boot_id.

.PP VSockCID exposes the system's local AF_VSOCK CID (Context Identifier, i.e. address) for the system, if one is available in the virtual machine environment. Set to UINT32_MAX otherwise. See vsock(7) for details.

.PP OperatingSystemSupportEnd exposes when the OS' vendor support ends, if this information is known. It's an unsigned 64bit value, in µs since the UNIX epoch, UTC. If this information is not known carries the value 2^64-1, i.e. UINT64_MAX.

.PP OperatingSystemImageID and OperatingSystemImageVersion expose the OS image name and version if available, or contain empty strings otherwise. This mostly corresponds to the IMAGE_ID= and IMAGE_VERSION= fields of the os-release file.

.PP HardwareVendor, HardwareModel, HardwareSKU, and HardwareVersion expose vendor information about the hardware of the system. The stock keeping unit (SKU) describes a distinct type of hardware for sale, purchase or inventory management. The SKU and version are only available if they deviate from the model and among each other. Thereby the version is more specific and only available if it differs from the model and SKU. If no such information can be determined these properties are set to empty strings.

.PP FirmwareVersion and FirmwareVendor expose information about the system's firmware, i.e. a version string and a vendor name. If no such information can be determined these properties are set to empty strings.

.PP FirmwareDate exposes the firmware build date, if that information is known. It's an unsigned 64bit value, in µs since the UNIX epoch, UTC. If not known UNIT64_MAX.

.PP ChassisAssetTag exposes an unique identifier of the system chassis. If this information is not known this property is set to an empty string.

.SS "Methods"

.PP 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.

.PP 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.

.PP SetPrettyHostname() sets the pretty hostname which is exposed by the PrettyHostname property.

.PP 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.

.PP SetTags() sets the machine tags exposed by the Tags property. It takes a list of strings, each of which must be a valid machine tag (1...255 ASCII alphanumeric characters, - and .). Passing an empty list removes the TAGS= field from /etc/machine-info.

.PP AddAndRemoveTags() incrementally updates the Tags property instead of replacing it. It takes two lists of machine tags: the tags in add are added to the current list, and the tags in remove are dropped from it (the resulting list is (current ∪ add) \ remove, sorted and deduplicated). This is useful when several independent agents each manage a subset of the tags without racing on a read-modify-write of the full list. Each tag must be a valid machine tag, as for SetTags().

.PP PrettyHostname, IconName, Chassis, Deployment, Location, and Tags are stored in /etc/machine-info. See machine-info(5) for the semantics of those settings.

.PP 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.

.PP GetHardwareSerial() returns the "hardware serial" as exposed by the kernel based on DMI information. Reading the file directly requires root privileges, and this method allows access to unprivileged clients through the polkit framework.

.PP Describe() returns a JSON representation of all properties in one.

.PP GetMachineInfo() returns the value of the given field from /etc/machine-info. For well-known fields, this method reads values from the same internal cache used by the corresponding D-Bus property getters, but returns only the raw /etc/machine-info values (i.e. without property-level fallback logic such as DMI/chassis-based detection). Custom (non-standard) fields are read directly from the file. An error is returned if the field name is empty, invalid, or not set in the file.

.SS "Security"

.PP The interactive boolean parameters can be used to control whether polkit should interactively ask the user for authentication credentials if required.

.PP 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(), SetLocation(), SetTags() and AddAndRemoveTags() it is org.freedesktop.hostname1.set-machine-info.

.SH "RECOMMENDATIONS"

.PP Here are three examples that show how the pretty hostname and the icon name should be used:

.PP 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(8).

.PP Here are some recommendations to follow when generating a static (internet) hostname from a pretty name:

.PP 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.

.PP Here are a couple of example conversions:

.PP 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.

.SH "EXAMPLES"

.PP Example 1. Introspect org.freedesktop.hostname1 on the bus

$ gdbus introspect --system \


  --dest org.freedesktop.hostname1 \


  --object-path /org/freedesktop/hostname1

.SH "VERSIONING"

.PP These D-Bus interfaces follow the usual interface versioning guidelines[2].

.SH "HISTORY"

.SS "The D-Bus API"

.PP FirmwareVersion and GetHardwareSerial() were added in version 251.

.PP OperatingSystemSupportEnd, FirmwareVendor, and FirmwareDate were added in version 253.

.PP MachineID, BootID and VSockCID were added in version 256.

.PP ChassisAssetTag, OperatingSystemImageID, OperatingSystemImageVersion, HardwareSKU, and HardwareVersion were added in version 258.

.PP OperatingSystemFancyName was added in version 260.

.PP GetMachineInfo(), Tags and SetTags() were added in version 261.

.PP AddAndRemoveTags() was added in version 262.

.SH "SEE ALSO"

.PP systemd(1), systemd-hostnamed.service(8), hostnamectl(1), David Zeuthen's original Fedora Feature page about xdg-hostname[3]