-.\"
+.\"
.\" dbus-daemon manual page.
.\" Copyright (C) 2003,2008 Red Hat, Inc.
.\"
[\-\-print-address[=DESCRIPTOR]] [\-\-print-pid[=DESCRIPTOR]] [\-\-fork]
.SH DESCRIPTION
-
\fIdbus-daemon\fP is the D-Bus message bus daemon. See
http://www.freedesktop.org/software/dbus/ for more information about
the big picture. D-Bus is first a library that provides one-to-one
application that uses this library to implement a message bus
daemon. Multiple programs connect to the message bus daemon and can
exchange messages with one another.
-
.PP
-There are two standard message bus instances: the systemwide message bus
-(installed on many systems as the "messagebus" init service) and the
+There are two standard message bus instances: the systemwide message bus
+(installed on many systems as the "messagebus" init service) and the
per-user-login-session message bus (started each time a user logs in).
-\fIdbus-daemon\fP is used for both of these instances, but with
+\fIdbus-daemon\fP is used for both of these instances, but with
a different configuration file.
-
.PP
The \-\-session option is equivalent to
"\-\-config-file=@EXPANDED_SYSCONFDIR@/dbus-1/session.conf" and the \-\-system
option is equivalent to
-"\-\-config-file=@EXPANDED_SYSCONFDIR@/dbus-1/system.conf". By creating
+"\-\-config-file=@EXPANDED_SYSCONFDIR@/dbus-1/system.conf". By creating
additional configuration files and using the \-\-config-file option,
additional special-purpose message bus daemons could be created.
-
.PP
-The systemwide daemon is normally launched by an init script,
-standardly called simply "messagebus".
-
+The systemwide daemon is normally launched by an init script,
+standardly called simply "messagebus".
.PP
-The systemwide daemon is largely used for broadcasting system events,
+The systemwide daemon is largely used for broadcasting system events,
such as changes to the printer queue, or adding/removing devices.
-
.PP
-The per-session daemon is used for various interprocess communication
-among desktop applications (however, it is not tied to X or the GUI
+The per-session daemon is used for various interprocess communication
+among desktop applications (however, it is not tied to X or the GUI
in any way).
-
.PP
SIGHUP will cause the D-Bus daemon to PARTIALLY reload its
configuration file and to flush its user/group information caches. Some
Use the given configuration file.
.TP
.I "--fork"
-Force the message bus to fork and become a daemon, even if
+Force the message bus to fork and become a daemon, even if
the configuration file does not specify that it should.
In most contexts the configuration file already gets this
right, though.
+.I "--nofork"
+Force the message bus not to fork and become a daemon, even if
+the configuration file specifies that it should.
.TP
.I "--print-address[=DESCRIPTOR]"
-Print the address of the message bus to standard output, or
-to the given file descriptor. This is used by programs that
+Print the address of the message bus to standard output, or
+to the given file descriptor. This is used by programs that
launch the message bus.
.TP
.I "--print-pid[=DESCRIPTOR]"
-Print the process ID of the message bus to standard output, or
-to the given file descriptor. This is used by programs that
+Print the process ID of the message bus to standard output, or
+to the given file descriptor. This is used by programs that
launch the message bus.
.TP
.I "--session"
.TP
.I "--version"
Print the version of the daemon.
+.TP
+.I "--introspect"
+Print the introspection information for all D-Bus internal interfaces.
+.TP
+.I "--address[=ADDRESS]"
+Set the address to listen on. This option overrides the address
+configured in the configuration file.
+.TP
+.I "--systemd-activation"
+Enable systemd-style service activation. Only useful in conjunction
+with the systemd system and session manager on Linux.
.SH CONFIGURATION FILE
A message bus daemon has a configuration file that specializes it
-for a particular application. For example, one configuration
-file might set up the message bus to be a systemwide message bus,
+for a particular application. For example, one configuration
+file might set up the message bus to be a systemwide message bus,
while another might set it up to be a per-user-login-session bus.
-
.PP
The configuration file also establishes resource limits, security
parameters, and so forth.
-
.PP
The configuration file is not part of any interoperability
specification and its backward compatibility is not guaranteed; this
document is documentation, not specification.
-
.PP
The standard systemwide and per-session message bus setups are
configured in the files "@EXPANDED_SYSCONFDIR@/dbus-1/system.conf" and
.TP
.I "<busconfig>"
-
+
.PP
Root element.
.TP
.I "<include>"
-
-.PP
+
+.PP
Include a file <include>filename.conf</include> at this point. If the
filename is relative, it is located relative to the configuration file
doing the including.
.PP
<include> has an optional attribute "ignore_missing=(yes|no)"
-which defaults to "no" if not provided. This attribute
-controls whether it's a fatal error for the included file
+which defaults to "no" if not provided. This attribute
+controls whether it's a fatal error for the included file
to be absent.
.TP
.PP
The user is changed after the bus has completed initialization. So
sockets etc. will be created before changing user, but no data will be
-read from clients before changing user. This means that sockets
-and PID files can be created in a location that requires root
+read from clients before changing user. This means that sockets
+and PID files can be created in a location that requires root
privileges for writing.
.TP
.I "<fork>"
-
+
.PP
-If present, the bus daemon becomes a real daemon (forks
-into the background, etc.). This is generally used
+If present, the bus daemon becomes a real daemon (forks
+into the background, etc.). This is generally used
rather than the \-\-fork command line option.
.TP
.I "<keep_umask>"
-
+
.PP
If present, the bus daemon keeps its original umask when forking.
This may be useful to avoid affecting the behavior of child processes.
.I "<listen>"
.PP
-Add an address that the bus should listen on. The
-address is in the standard D-Bus format that contains
+Add an address that the bus should listen on. The
+address is in the standard D-Bus format that contains
a transport name plus possible parameters/options.
.PP
Example: <listen>tcp:host=localhost,port=1234</listen>
.PP
-If there are multiple <listen> elements, then the bus listens
-on multiple addresses. The bus will pass its address to
-started services or other interested parties with
-the last address given in <listen> first. That is,
+If there are multiple <listen> elements, then the bus listens
+on multiple addresses. The bus will pass its address to
+started services or other interested parties with
+the last address given in <listen> first. That is,
apps will try to connect to the last <listen> address first.
.PP
exist, then all known mechanisms are allowed. If there are multiple
<auth> elements, all the listed mechanisms are allowed. The order in
which mechanisms are listed is not meaningful.
-
+
.PP
Example: <auth>EXTERNAL</auth>
.PP
Adds a directory to scan for .service files. Directories are
-scanned starting with the last to appear in the config file
-(the first .service file found that provides a particular
+scanned starting with the last to appear in the config file
+(the first .service file found that provides a particular
service will be used).
.PP
Service files tell the bus how to automatically start a program.
-They are primarily used with the per-user-session bus,
+They are primarily used with the per-user-session bus,
not the systemwide bus.
.TP
"max_message_size" : max size of a single message in
bytes
"max_message_unix_fds" : max unix fds of a single message
- "service_start_timeout" : milliseconds (thousandths) until
+ "service_start_timeout" : milliseconds (thousandths) until
a started service has to connect
"auth_timeout" : milliseconds (thousandths) a
connection is given to
authenticate
- "max_completed_connections" : max number of authenticated connections
+ "max_completed_connections" : max number of authenticated connections
"max_incomplete_connections" : max number of unauthenticated
connections
"max_connections_per_user" : max number of completed connections from
the same user
"max_pending_service_starts" : max number of service launches in
progress at the same time
- "max_names_per_connection" : max number of names a single
+ "max_names_per_connection" : max number of names a single
connection can own
- "max_match_rules_per_connection": max number of match rules for a single
+ "max_match_rules_per_connection": max number of match rules for a single
connection
- "max_replies_per_connection" : max number of pending method
+ "max_replies_per_connection" : max number of pending method
replies per connection
(number of calls-in-progress)
- "reply_timeout" : milliseconds (thousandths)
- until a method call times out
+ "reply_timeout" : milliseconds (thousandths)
+ until a method call times out
.fi
.PP
up all connections on the systemwide bus.
.PP
-Limits are normally only of interest on the systemwide bus, not the user session
+Limits are normally only of interest on the systemwide bus, not the user session
buses.
.TP
The <policy> element defines a security policy to be applied to a particular
set of connections to the bus. A policy is made up of
<allow> and <deny> elements. Policies are normally used with the systemwide bus;
-they are analogous to a firewall in that they allow expected traffic
+they are analogous to a firewall in that they allow expected traffic
and prevent unexpected traffic.
.PP
-Currently, the system bus has a default-deny policy for sending method calls
+Currently, the system bus has a default-deny policy for sending method calls
and owning bus names. Everything else, in particular reply messages, receive
checks, and signals has a default allow policy.
.fi
.PP
-Policies applied later will override those applied earlier,
-when the policies overlap. Multiple policies with the same
-user/group/context are applied in the order they appear
+Policies applied later will override those applied earlier,
+when the policies overlap. Multiple policies with the same
+user/group/context are applied in the order they appear
in the config file.
.TP
The possible attributes of these elements are:
.nf
send_interface="interface_name"
- send_member="method_or_signal_name"
- send_error="error_name"
- send_destination="name"
- send_type="method_call" | "method_return" | "signal" | "error"
+ send_member="method_or_signal_name"
+ send_error="error_name"
+ send_destination="name"
+ send_type="method_call" | "method_return" | "signal" | "error"
send_path="/path/name"
receive_interface="interface_name"
- receive_member="method_or_signal_name"
- receive_error="error_name"
- receive_sender="name"
+ receive_member="method_or_signal_name"
+ receive_error="error_name"
+ receive_sender="name"
receive_type="method_call" | "method_return" | "signal" | "error"
receive_path="/path/name"
.PP
Examples:
.nf
- <deny send_destination="org.freedesktop.Service" send_interface="org.freedesktop.System" send_member="Reboot"/>
+ <deny send_destination="org.freedesktop.Service" send_interface="org.freedesktop.System" send_member="Reboot"/>
<deny send_destination="org.freedesktop.System"/>
<deny receive_sender="org.freedesktop.System"/>
<deny user="john"/>
The <deny> element's attributes determine whether the deny "matches" a
particular action. If it matches, the action is denied (unless later
rules in the config file allow it).
-
.PP
send_destination and receive_sender rules mean that messages may not be
sent to or received from the *owner* of the given name, not that
they may not be sent *to that name*. That is, if a connection
owns services A, B, C, and sending to A is denied, sending to B or C
will not work either.
-
.PP
The other send_* and receive_* attributes are purely textual/by-value
matches against the given field in the message header.
-
.PP
"Eavesdropping" occurs when an application receives a message that
was explicitly addressed to a name the application does not own, or
is a reply to such a message. Eavesdropping thus only applies to
messages that are addressed to services and replies to such messages
(i.e. it does not apply to signals).
-
.PP
-For <allow>, eavesdrop="true" indicates that the rule matches even
-when eavesdropping. eavesdrop="false" is the default and means that
+For <allow>, eavesdrop="true" indicates that the rule matches even
+when eavesdropping. eavesdrop="false" is the default and means that
the rule only allows messages to go to their specified recipient.
-For <deny>, eavesdrop="true" indicates that the rule matches
+For <deny>, eavesdrop="true" indicates that the rule matches
only when eavesdropping. eavesdrop="false" is the default for <deny>
-also, but here it means that the rule applies always, even when
+also, but here it means that the rule applies always, even when
not eavesdropping. The eavesdrop attribute can only be combined with
send and receive rules (with send_* and receive_* attributes).
-
-
.PP
The [send|receive]_requested_reply attribute works similarly to the eavesdrop
attribute. It controls whether the <deny> or <allow> matches a reply
always, regardless of pending reply state.
.PP
-user and group denials mean that the given user or group may
+user and group denials mean that the given user or group may
not connect to the message bus.
.PP
received" are evaluated separately.
.PP
-Be careful with send_interface/receive_interface, because the
+Be careful with send_interface/receive_interface, because the
interface field in messages is optional. In particular, do NOT
specify <deny send_interface="org.foo.Bar"/>! This will cause
no-interface messages to be blocked for all services, which is
An <associate> element appears below an <selinux> element and
creates a mapping. Right now only one kind of association is possible:
.nf
- <associate own="org.freedesktop.Foobar" context="foo_t"/>
+ <associate own="org.freedesktop.Foobar" context="foo_t"/>
.fi
.PP
This means that if a connection asks to own the name
"org.freedesktop.Foobar" then the source context will be the context
-of the connection and the target context will be "foo_t" - see the
+of the connection and the target context will be "foo_t" - see the
short discussion of SELinux below.
.PP
There's currently no way to set a default for owning any name, if
we add this syntax it will look like:
.nf
- <associate own="*" context="foo_t"/>
+ <associate own="*" context="foo_t"/>
.fi
If you find a reason this is useful, let the developers know.
Right now the default will be the security context of the bus itself.
as target, object class "dbus" and requested permission "send_msg".
.PP
-If a security context is not available for a connection
-(impossible when using UNIX domain sockets), then the target
+If a security context is not available for a connection
+(impossible when using UNIX domain sockets), then the target
context used is the context of the bus daemon itself.
-There is currently no way to change this default, because we're
-assuming that only UNIX domain sockets will be used to
-connect to the systemwide bus. If this changes, we'll
+There is currently no way to change this default, because we're
+assuming that only UNIX domain sockets will be used to
+connect to the systemwide bus. If this changes, we'll
probably add a way to set the default connection context.
.PP
-Second, any time a connection asks to own a name,
-the bus daemon will check permissions with the security
+Second, any time a connection asks to own a name,
+the bus daemon will check permissions with the security
context of the connection as source, the security context specified
-for the name in the config file as target, object
+for the name in the config file as target, object
class "dbus" and requested permission "acquire_svc".
.PP
-The security context for a bus name is specified with the
+The security context for a bus name is specified with the
<associate> element described earlier in this document.
-If a name has no security context associated in the
-configuration file, the security context of the bus daemon
+If a name has no security context associated in the
+configuration file, the security context of the bus daemon
itself will be used.
.SH DEBUGGING
.PP
If you're trying to figure out where your messages are going or why
you aren't getting messages, there are several things you can try.
-
.PP
Remember that the system bus is heavily locked down and if you
haven't installed a security policy file to allow your message
through, it won't work. For the session bus, this is not a concern.
-
.PP
The simplest way to figure out what's happening on the bus is to run
the \fIdbus-monitor\fP program, which comes with the D-Bus
package. You can also send test messages with \fIdbus-send\fP. These
programs have their own man pages.
-
.PP
If you want to know what the daemon itself is doing, you might consider
-running a separate copy of the daemon to test against. This will allow you
-to put the daemon under a debugger, or run it with verbose output, without
+running a separate copy of the daemon to test against. This will allow you
+to put the daemon under a debugger, or run it with verbose output, without
messing up your real session and system daemons.
-
.PP
-To run a separate test copy of the daemon, for example you might open a terminal
-and type:
+To run a separate test copy of the daemon, for example you might open a terminal
+and type:
.nf
DBUS_VERBOSE=1 dbus-daemon --session --print-address
.fi
-
.PP
The test daemon address will be printed when the daemon starts. You will need
-to copy-and-paste this address and use it as the value of the
+to copy-and-paste this address and use it as the value of the
DBUS_SESSION_BUS_ADDRESS environment variable when you launch the applications
-you want to test. This will cause those applications to connect to your
+you want to test. This will cause those applications to connect to your
test bus instead of the DBUS_SESSION_BUS_ADDRESS of your real session bus.
-
.PP
DBUS_VERBOSE=1 will have NO EFFECT unless your copy of D-Bus
was compiled with verbose mode enabled. This is not recommended in
production builds due to performance impact. You may need to rebuild
D-Bus if your copy was not built with debugging in mind. (DBUS_VERBOSE
-also affects the D-Bus library and thus applications using D-Bus; it may
+also affects the D-Bus library and thus applications using D-Bus; it may
be useful to see verbose output on both the client side and from the daemon.)
-
.PP
If you want to get fancy, you can create a custom bus
configuration for your test bus (see the session.conf and system.conf
would allow you to specify a different directory for .service files,
for example.
-
.SH AUTHOR
See http://www.freedesktop.org/software/dbus/doc/AUTHORS
projects / platform / upstream / dbus.git / commitdiff