Provided by: dbus_1.4.0-0ubuntu1_i386 bug

NAME

       dbus-daemon - Message bus daemon

SYNOPSIS

       dbus-daemon  dbus-daemon  [--version] [--session] [--system] [--config-
       file=FILE]  [--print-address[=DESCRIPTOR]]   [--print-pid[=DESCRIPTOR]]
       [--fork]

DESCRIPTION

       dbus-daemon     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
       communication  between  any  two  applications;   dbus-daemon   is   an
       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.

       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).  dbus-daemon is used for both  of  these  instances,  but  with  a
       different configuration file.

       The     --session     option     is     equivalent     to    "--config-
       file=/etc/dbus-1/session.conf" and the --system option is equivalent to
       "--config-file=/etc/dbus-1/system.conf".    By    creating   additional
       configuration files and  using  the  --config-file  option,  additional
       special-purpose message bus daemons could be created.

       The   systemwide  daemon  is  normally  launched  by  an  init  script,
       standardly called simply "messagebus".

       The systemwide daemon is largely used for broadcasting  system  events,
       such as changes to the printer queue, or adding/removing devices.

       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).

       SIGHUP   will   cause   the   D-Bus  daemon  to  PARTIALLY  reload  its
       configuration file and to flush its user/group information caches. Some
       configuration  changes  would  require kicking all apps off the bus; so
       they will only take effect if you restart the  daemon.  Policy  changes
       should take effect with SIGHUP.

OPTIONS

       The following options are supported:

       --config-file=FILE
              Use the given configuration file.

       --fork 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.
              --nofork Force the message bus not to fork and become a  daemon,
              even if the configuration file specifies that it should.

       --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  launch
              the message bus.

       --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
              launch the message bus.

       --session
              Use  the  standard  configuration file for the per-login-session
              message bus.

       --system
              Use the standard configuration file for the  systemwide  message
              bus.

       --version
              Print the version of the daemon.

       --introspect
              Print  the  introspection  information  for  all  D-Bus internal
              interfaces.

       --address[=ADDRESS]
              Set the address to listen on. This option overrides the  address
              configured in the configuration file.

       --systemd-activation
              Enable   systemd-style   service   activation.  Only  useful  in
              conjunction with the  systemd  system  and  session  manager  on
              Linux.

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, while another might
       set it up to be a per-user-login-session bus.

       The configuration  file  also  establishes  resource  limits,  security
       parameters, and so forth.

       The   configuration   file   is   not   part  of  any  interoperability
       specification and its backward compatibility is  not  guaranteed;  this
       document is documentation, not specification.

       The   standard  systemwide  and  per-session  message  bus  setups  are
       configured    in    the     files     "/etc/dbus-1/system.conf"     and
       "/etc/dbus-1/session.conf".   These  files normally <include> a system-
       local.conf or session-local.conf; you can put local overrides in  those
       files to avoid modifying the primary configuration files.

       The  configuration  file is an XML document. It must have the following
       doctype declaration:

          <!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-Bus Bus Configuration 1.0//EN"
           "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">

       The following elements may be present in the configuration file.

       <busconfig>

       Root element.

       <type>

       The well-known type of the message  bus.  Currently  known  values  are
       "system"  and "session"; if other values are set, they should be either
       added to the D-Bus  specification,  or  namespaced.   The  last  <type>
       element  "wins"  (previous  values  are  ignored).  This  element  only
       controls which message bus specific environment variables  are  set  in
       activated clients.  Most of the policy that distinguishes a session bus
       from the system bus is  controlled  from  the  other  elements  in  the
       configuration file.

       If  the  well-known  type  of  the  message  bus is "session", then the
       DBUS_STARTER_BUS_TYPE environment variable will be set to "session" and
       the  DBUS_SESSION_BUS_ADDRESS  environment  variable will be set to the
       address of the session bus.  Likewise, if the type of the  message  bus
       is  "system",  then the DBUS_STARTER_BUS_TYPE environment variable will
       be  set  to  "system"  and  the  DBUS_SESSION_BUS_ADDRESS   environment
       variable  will  be  set  to  the  address  of  the system bus (which is
       normally well known anyway).

       Example: <type>session</type>

       <include>

       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.

       <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 to be absent.

       <includedir>

       Include all files  in  <includedir>foo.d</includedir>  at  this  point.
       Files  in  the  directory  are included in undefined order.  Only files
       ending in ".conf" are included.

       This is intended to allow extension of the  system  bus  by  particular
       packages.   For  example,  if  CUPS  wants  to  be  able  to  send  out
       notification of printer queue changes,  it  could  install  a  file  to
       /etc/dbus-1/system.d  that allowed all apps to receive this message and
       allowed the printer daemon user to send it.

       <user>

       The user account the daemon should run as, as either a  username  or  a
       UID.  If the daemon cannot change to this UID on startup, it will exit.
       If this element is not present, the daemon  will  not  change  or  care
       about its UID.

       The last <user> entry in the file "wins", the others are ignored.

       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  privileges  for
       writing.

       <fork>

       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.

       <keep_umask>

       If present, the bus daemon keeps its original umask when forking.  This
       may be useful to avoid affecting the behavior of child processes.

       <listen>

       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.

       Example: <listen>unix:path=/tmp/foo</listen>

       Example: <listen>tcp:host=localhost,port=1234</listen>

       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.

       tcp sockets can accept IPv4 addresses, IPv6 addresses or hostnames.  If
       a  hostname resolves to multiple addresses, the server will bind to all
       of them. The family=ipv4 or family=ipv6 options can be used to force it
       to bind to a subset of addresses

       Example: <listen>tcp:host=localhost,port=0,family=ipv4</listen>

       A  special  case is using a port number of zero (or omitting the port),
       which means to choose an  available  port  selected  by  the  operating
       system. The port number chosen can be obtained with the --print-address
       command line parameter and will be present in  other  cases  where  the
       server  reports  its own address, such as when DBUS_SESSION_BUS_ADDRESS
       is set.

       Example: <listen>tcp:host=localhost,port=0</listen>

       tcp addresses also allow a bind=hostname option,  which  will  override
       the  host  option  specifying what address to bind to, without changing
       the address reported by the bus.  The  bind  option  can  also  take  a
       special  name  '*'  to  cause  the  bus  to listen on all local address
       (INADDR_ANY). The specified host should be a valid name  of  the  local
       machine or weird stuff will happen.

       Example: <listen>tcp:host=localhost,bind=*,port=0</listen>

       <auth>

       Lists  permitted  authorization  mechanisms.  If  this  element doesn't
       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.

       Example: <auth>EXTERNAL</auth>

       Example: <auth>DBUS_COOKIE_SHA1</auth>

       <servicedir>

       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 service will be used).

       Service files tell the bus how to automatically start a program.   They
       are  primarily  used  with the per-user-session bus, not the systemwide
       bus.

       <standard_session_servicedirs/>

       <standard_session_servicedirs/> is equivalent to specifying a series of
       <servicedir/>  elements  for  each  of the data directories in the "XDG
       Base Directory Specification" with the subdirectory  "dbus-1/services",
       so   for   example  "/usr/share/dbus-1/services"  would  be  among  the
       directories searched.

       The   "XDG   Base   Directory   Specification"   can   be   found    at
       http://freedesktop.org/wiki/Standards/basedir-spec  if it hasn't moved,
       otherwise try your favorite search engine.

       The <standard_session_servicedirs/> option is only relevant to the per-
       user-session bus daemon defined in /etc/dbus-1/session.conf. Putting it
       in any other configuration file would probably be nonsense.

       <standard_system_servicedirs/>

       <standard_system_servicedirs/>  specifies  the   standard   system-wide
       activation directories that should be searched for service files.  This
       option defaults to /usr/share/dbus-1/system-services.

       The <standard_system_servicedirs/> option is only relevant to the  per-
       system bus daemon defined in /etc/dbus-1/system.conf. Putting it in any
       other configuration file would probably be nonsense.

       <servicehelper/>

       <servicehelper/> specifies the setuid helper that  is  used  to  launch
       system  daemons  with  an  alternate user. Typically this should be the
       dbus-daemon-launch-helper executable in located in libexec.

       The <servicehelper/> option is only  relevant  to  the  per-system  bus
       daemon  defined  in  /etc/dbus-1/system.conf.  Putting  it in any other
       configuration file would probably be nonsense.

       <limit>

       <limit> establishes a resource limit. For example:
         <limit name="max_message_size">64</limit>
         <limit name="max_completed_connections">512</limit>

       The name attribute is mandatory.  Available limit names are:
             "max_incoming_bytes"         : total size in bytes of messages
                                            incoming from a single connection
             "max_incoming_unix_fds"      : total number of unix fds of messages
                                            incoming from a single connection
             "max_outgoing_bytes"         : total size in bytes of messages
                                            queued up for a single connection
             "max_outgoing_unix_fds"      : total number of unix fds of messages
                                            queued up for a single connection
             "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
                                            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_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
                                            connection can own
             "max_match_rules_per_connection": max number of match rules for a single
                                               connection
             "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

       The max incoming/outgoing queue sizes allow a new message to be  queued
       if one byte remains below the max. So you can in fact exceed the max by
       max_message_size.

       max_completed_connections divided by  max_connections_per_user  is  the
       number  of  users that can work together to denial-of-service all other
       users by using up all connections on the systemwide bus.

       Limits are normally only of interest on the  systemwide  bus,  not  the
       user session buses.

       <policy>

       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 and prevent unexpected traffic.

       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.

       In  general,  it  is  best  to  keep system services as small, targeted
       programs which run in their own process and provide a single bus  name.
       Then, all that is needed is an <allow> rule for the "own" permission to
       let the process claim the bus name, and a  "send_destination"  rule  to
       allow traffic from some or all uids to your service.

       The <policy> element has one of four attributes:
         context="(default|mandatory)"
         at_console="(true|false)"
         user="username or userid"
         group="group name or gid"

       Policies are applied to a connection as follows:
          - all context="default" policies are applied
          - all group="connection's user's group" policies are applied
            in undefined order
          - all user="connection's auth user" policies are applied
            in undefined order
          - all at_console="true" policies are applied
          - all at_console="false" policies are applied
          - all context="mandatory" policies are applied

       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.

       <deny> <allow>

       A  <deny>  element  appears below a <policy> element and prohibits some
       action. The <allow> element  makes  an  exception  to  previous  <deny>
       statements, and works just like <deny> but with the inverse meaning.

       The possible attributes of these elements are:
          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_path="/path/name"

          receive_interface="interface_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"

          send_requested_reply="true" | "false"
          receive_requested_reply="true" | "false"

          eavesdrop="true" | "false"

          own="name"
          user="username"
          group="groupname"

       Examples:
          <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"/>
          <deny group="enemies"/>

       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).

       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.

       The  other  send_* and receive_* attributes are purely textual/by-value
       matches against the given field in the message header.

       "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).

       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   only  when
       eavesdropping. eavesdrop="false" is the default for  <deny>  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).

       The  [send|receive]_requested_reply  attribute  works  similarly to the
       eavesdrop attribute. It controls whether the <deny> or <allow>  matches
       a  reply  that  is  expected  (corresponds  to  a  previous method call
       message).  This attribute only makes sense for reply  messages  (errors
       and method returns), and is ignored for other message types.

       For  <allow>,  [send|receive]_requested_reply="true" is the default and
       indicates  that  only  requested  replies  are  allowed  by  the  rule.
       [send|receive]_requested_reply="false"  means  that the rule allows any
       reply even if unexpected.

       For <deny>, [send|receive]_requested_reply="false" is the  default  but
       indicates  that the rule matches only when the reply was not requested.
       [send|receive]_requested_reply="true" indicates that the  rule  applies
       always, regardless of pending reply state.

       user  and  group  denials  mean  that  the  given user or group may not
       connect to the message bus.

       For "name", "username", "groupname", etc.  the  character  "*"  can  be
       substituted,  meaning  "any."  Complex  globs  like  "foo.bar.*" aren't
       allowed for now because they'd be work to implement and maybe encourage
       sloppy security anyway.

       It  does not make sense to deny a user or group inside a <policy> for a
       user or group; user/group denials can only be inside  context="default"
       or context="mandatory" policies.

       A  single  <deny>  rule  may specify combinations of attributes such as
       send_destination and send_interface and send_type. In  this  case,  the
       denial  applies only if both attributes match the message being denied.
       e.g. <deny send_interface="foo.bar" send_destination="foo.blah"/> would
       deny  messages with the given interface AND the given bus name.  To get
       an OR effect you specify multiple <deny> rules.

       You can't include both send_ and receive_ attributes on the same  rule,
       since  "whether  the  message  can  be  sent"  and  "whether  it can be
       received" are evaluated separately.

       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 almost certainly not what you
       intended.     Always    use    rules     of     the     form:     <deny
       send_interface="org.foo.Bar" send_destination="org.foo.Service"/>

       <selinux>

       The  <selinux>  element  contains settings related to Security Enhanced
       Linux.  More details below.

       <associate>

       An <associate> element appears below an <selinux> element and creates a
       mapping. Right now only one kind of association is possible:
          <associate own="org.freedesktop.Foobar" context="foo_t"/>

       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 short
       discussion of SELinux below.

       Note, the context here is the target context when  requesting  a  name,
       NOT the context of the connection owning the name.

       There's  currently  no  way to set a default for owning any name, if we
       add this syntax it will look like:
          <associate own="*" context="foo_t"/>
       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.

       If  two  <associate>  elements  specify  the  same  name,  the  element
       appearing later in the configuration file will be used.

SELinux

       See http://www.nsa.gov/selinux/  for  full  details  on  SELinux.  Some
       useful excerpts:

               Every  subject  (process)  and  object  (e.g. file, socket, IPC
               object, etc) in the system is assigned a collection of security
               attributes,  known  as  a  security context. A security context
               contains all of  the  security  attributes  associated  with  a
               particular  subject or object that are relevant to the security
               policy.

               In order to better encapsulate security contexts and to provide
               greater  efficiency,  the  policy  enforcement  code of SELinux
               typically  handles  security  identifiers  (SIDs)  rather  than
               security  contexts.  A  SID is an integer that is mapped by the
               security server to a security context at runtime.

               When a security decision is required,  the  policy  enforcement
               code  passes a pair of SIDs (typically the SID of a subject and
               the SID of an object, but sometimes a pair of subject SIDs or a
               pair  of  object  SIDs),  and  an  object security class to the
               security server. The object security class indicates  the  kind
               of  object,  e.g. a process, a regular file, a directory, a TCP
               socket, etc.

               Access decisions specify whether or not a permission is granted
               for a given pair of SIDs and class. Each object class has a set
               of associated permissions  defined  to  control  operations  on
               objects with that class.

       D-Bus performs SELinux security checks in two places.

       First,  any  time  a  message  is routed from one connection to another
       connection, the bus daemon will check  permissions  with  the  security
       context  of  the  first  connection  as source, security context of the
       second  connection  as  target,  object  class  "dbus"  and   requested
       permission "send_msg".

       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
       probably add a way to set the default connection context.

       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 class "dbus" and requested permission "acquire_svc".

       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 itself will be used.

DEBUGGING

       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.

       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.

       The  simplest  way  to figure out what's happening on the bus is to run
       the dbus-monitor program, which comes with the D-Bus package.  You  can
       also  send  test messages with dbus-send. These programs have their own
       man pages.

       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 messing up your real session and system daemons.

       To run a separate test copy of the daemon, for example you might open a
       terminal and type:
         DBUS_VERBOSE=1 dbus-daemon --session --print-address

       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
       DBUS_SESSION_BUS_ADDRESS  environment  variable  when  you  launch  the
       applications  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.

       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 be useful to see verbose output on both the client  side  and  from
       the daemon.)

       If you want to get fancy, you can create a custom bus configuration for
       your test bus (see the session.conf and system.conf files  that  define
       the  two  default  configurations for example). This would allow you to
       specify a different directory for .service files, for example.

AUTHOR

       See http://www.freedesktop.org/software/dbus/doc/AUTHORS

BUGS

       Please send bug reports to the D-Bus mailing list or bug  tracker,  see
       http://www.freedesktop.org/software/dbus/

                                                                dbus-daemon(1)