org.freedesktop.hostname1(5) - man - phpMan

ORG.FREEDESKTOP.HOSTNAME1(5)          org.freedesktop.hostname1         ORG.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);
                 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[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(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.

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
           http://0pointer.de/blog/projects/versioning-dbus.html

        3. Feature page about xdg-hostname
           https://fedoraproject.org/wiki/Features/BetterHostname



systemd 249                                                             ORG.FREEDESKTOP.HOSTNAME1(5)