"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
+ SPDX-License-Identifier: LGPL-2.1+
+
This file is part of systemd.
Copyright 2014 Zbigniew Jędrzejewski-Szmek
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_bus_default">
connection object to the user bus when invoked in user context, or
to the system bus otherwise. The connection object is associated
with the calling thread. Each time the function is invoked from
- the same thread the same object is returned, but its reference
+ the same thread, the same object is returned, but its reference
count is increased by one, as long as at least one reference is
kept. When the last reference to the connection is dropped (using
the
call), the connection is terminated. Note that the connection is
not automatically terminated when the associated thread ends. It
is important to drop the last reference to the bus connection
- explicitly before the thread ends or otherwise the connection will
- be leaked. Also, queued but unread or unwritten messages keep the
+ explicitly before the thread ends, as otherwise, the connection will
+ leak. Also, queued but unread or unwritten messages keep the
bus referenced, see below.</para>
<para><function>sd_bus_default_user()</function> returns a user
<function>sd_bus_open_system()</function> does the same, but
connects to the system bus. In contrast to
<function>sd_bus_default()</function>,
- <function>sd_bus_default_user()</function>,
- <function>sd_bus_default_system()</function> these calls return
+ <function>sd_bus_default_user()</function>, and
+ <function>sd_bus_default_system()</function>, these calls return
new, independent connection objects that are not associated with
the invoking thread and are not shared between multiple
invocations. It is recommended to share connections per thread to
efficiently make use the available resources. Thus, it is
recommended to use <function>sd_bus_default()</function>,
- <function>sd_bus_default_user()</function>,
+ <function>sd_bus_default_user()</function> and
<function>sd_bus_default_system()</function> to connect to the
user or system buses.</para>
not set, a suitable default for the default system D-Bus instance
will be used.</para>
- <para><function>sd_bus_open_system_remote()</function> connects to
- the system bus on the specified <parameter>host</parameter> using
- <citerefentry
- project='die-net'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>. <parameter>host</parameter>
- consists of an optional user name followed by the
- <literal>@</literal> symbol, and the hostname.
- </para>
+ <para><function>sd_bus_open_system_remote()</function> connects to the system bus on
+ the specified host using
+ <citerefentry project='die-net'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
+ <parameter>host</parameter> consists of an optional user name followed by the
+ <literal>@</literal> symbol, and the hostname, optionally followed by a
+ <literal>:</literal> and a machine name. If the machine name is given, a connection
+ is created to the system bus in the specified container on the remote machine, and
+ otherwise a connection to the system bus on the specified host is created.</para>
+
+ <para>Note that entering a container is a privileged operation, and will likely only
+ work for the root user on the remote machine.</para>
<para><function>sd_bus_open_system_machine()</function> connects
to the system bus in the specified <parameter>machine</parameter>,
<para>Queued but unwritten/unread messages also keep a reference
to their bus connection object. For this reason, even if an
- application dropped all references to a bus connection it might
- not get destroyed right-away. Until all incoming queued
+ application dropped all references to a bus connection, it might
+ not get destroyed right away. Until all incoming queued
messages are read, and until all outgoing unwritten messages are
written, the bus object will stay
alive. <function>sd_bus_flush()</function> may be used to write
all outgoing queued messages so they drop their references. To
- flush the unread incoming messages use
+ flush the unread incoming messages, use
<function>sd_bus_close()</function>, which will also close the bus
- connection. When using the default bus logic it is a good idea to
+ connection. When using the default bus logic, it is a good idea to
first invoke <function>sd_bus_flush()</function> followed by
<function>sd_bus_close()</function> when a thread or process
terminates, and thus its bus connection object should be
freed.</para>
- <para>The life-cycle of the default bus connection should be the
+ <para>The life cycle of the default bus connection should be the
responsibility of the code that creates/owns the thread the
default bus connection object is associated with. Library code
should neither call <function>sd_bus_flush()</function> nor
<function>sd_bus_close()</function> on default bus objects unless
it does so in its own private, self-allocated thread. Library code
should not use the default bus object in other threads unless it
- is clear that the program using it will life-cycle the bus
+ is clear that the program using it will life cycle the bus
connection object and flush and close it before exiting from the
thread. In libraries where it is not clear that the calling
- program will life-cycle the bus connection object it is hence
+ program will life cycle the bus connection object, it is hence
recommended to use <function>sd_bus_open_system()</function>
instead of <function>sd_bus_default_system()</function> and
related calls.</para>