Windows PowerShell command on Get-command dbus-daemon

Manual Pages for UNIX Operating System command usage for man dbus-daemon

C Library Functions dbus-daemon(3)

NAME

dbus-daemon - Message bus daemon

SYNOPSIS

dbus-daemon [--config-file=file] [--fork | --nofork] [--

introspect] [--print-address[=descriptor]] [--print-

pid[=descriptor]] [--session] [--system] [--version]

DESCRIPTION

dbus-daemon is the D-Bus message bus daemon. 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. dbus-daemon

is used for both of these instances, but with a different configuration file.

+o systemwide message bus - Launched when the system is

started and is enabled by default. Additional system-

wide services can be launched via D-Bus service activa-

tion However, D-Bus service activation is disabled on

Solaris. Note that the --system option is equivalent

to:

"--config-file=/etc/dbus-1/system.conf"

+o per-user-login-session message bus - Launched each time

a user logs in. Note that the --session option is

equivalent to:

"--config-file=/etc/dbus-1/session.conf"

By creating additional configuration files and using the --

config-file option, additional special-purpose message bus

daemons could be created.

On Solaris, D-Bus is configured with service activation dis-

abled, so that users cannot launch systemwide D-Bus services

on demand. This feature is not used by any applications that are currently shipped with Solaris.

On Solaris, the D-Bus service is managed by the smf(5) ser-

vice management facility under the service identifier svc:/system/dbus. On Solaris, it is recommended that you

use the svcadm(1m) utility to start and stop the D-Bus ser-

vice

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The systemwide daemon is largely used for broadcasting sys-

tem events, such as changes to the printer queue, or adding/removing devices.

The per-session daemon is used for various interprocess com-

munication 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 applications 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, regardless of configuration file settings.

--introspect

Print introspect data and exit.

--nofork

Avoid running the message bus as a daemon, regardless of configuration file settings.

--print-address[=descriptor]

Print the address of the message bus to standard output,

or to the given file descriptor. This is used by pro-

grams that launch the message bus.

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--print-pid[=descriptor]

Print the process ID of the message bus to standard out-

put, 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. ENVIRONMENT VARIABLES See environ(5) for descriptions of the following environment variables:

DBUS_SESSION_BUS_ADDRESS

The address of the login session message bus. If this variable is not set, applications may also try to read

the address from the X Window System root window pro-

perty _DBUS_SESSION_BUS_ADDRESS. The root window pro-

perty must have type STRING. The environment variable should have precedence over the root window property.

DBUS_STARTER_BUS_TYPE

If the well-known type of the message bus is "session",

then this environment variable will be set to "session". If the type of the message bus is "system;", then this environment variable will be set to "system".

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DBUS_VERBOSE

Set DBUS_VERSION=1 to enable debugging, if D-Bus was

compiled with verbose debug mode enabled. EXIT STATUS The following exit values are returned: 0 Application exited successfully >0 Application exited with failure

EXTENDED DESCRIPTION

CONFIGURATION FILE

A message bus daemon has a configuration file that special-

izes it for a particular application. For example, one con-

figuration file might set up the message bus to be a system-

wide 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 specifica-

tion.

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

a system-local.conf or session-local.conf; you can put local

overrides in those files to avoid modifying the primary con-

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

"http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd"> The following elements may be present in the configuration file.

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C Library Functions dbus-daemon(3)

Root element.

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 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 con-

figuration 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: session Include a file filename.conf at this point. If the filename is relative, it is located relative to the configuration file doing the including. has an optional attribute

"ignore_missing=(yes|no)" which defaults to "no" if not pro-

vided. This attribute controls whether it is a fatal error for the included file to be absent. Include all files in foo.d 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

applications to receive this message and allowed the printer daemon user to send it.

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C Library Functions dbus-daemon(3)

The user account the daemon should run as, specified 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 entry in the file "wins", the others are ignored.

The user is changed after the bus has completed initializa-

tion. 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. 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.

If present, the bus daemon keeps its original umask when forking. This may be useful to avoid affecting the behavior of child processes. 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: unix:path=/tmp/foo Example: tcp:host=localhost,port=1234 If there are multiple 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 first. That is, applica-

tions will try to connect to the last 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: tcp:host=localhost,port=0,family=ipv4

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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: tcp:host=localhost,port=0 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: tcp:host=localhost,bind=*,port=0 Lists permitted authorization mechanisms. If this element does not exist, then all known mechanisms are allowed. If

there are multiple elements, all the listed mechan-

isms are allowed. The order in which mechanisms are listed is not meaningful. Example: EXTERNAL

Example: DBUS_COOKIE_SHA1

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 particu-

lar service will be used).

Service files tell the bus how to automatically start a pro-

gram. They are primarily used with the per-user-session

bus, not the systemwide bus.

is equivalent to specifying

a series of 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" should be found at

http://freedesktop.org/wiki/Standards/basedir-spec.

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The option is only relevant

to the per-user-session bus daemon defined in

/etc/dbus-1/session.conf. Putting it in any other confi-

guration file would probably be nonsense.

specifies the standard sys-

temwide activation directories that should be searched for

service files. This option defaults to /usr/share/dbus-

1/system-services.

The option is only relevant

to the per-system bus daemon defined in

/etc/dbus-1/system.conf. Putting it in any other configura-

tion file would probably be nonsense. specifies the setuid helper that is used to launch system daemons with an alternate user. Typically

this would be the dbus-daemon-launch-helper executable.

Because D-Bus service activation is disabled on Solaris, the

dbus-daemon-launch-helper executable is not distributed with

Solaris.

The option is only relevant to the per-

system bus daemon defined in /etc/dbus-1/system.conf. Put-

ting it in any other configuration file would probably be nonsense. establishes a resource limit. For example:

512

The name attribute is mandatory. Available limit names are:

"max_incoming_bytes" : total size in bytes of

messages incoming from a single connection

"max_outgoing_bytes" : total size in bytes of

messages queued up for a single connection

"max_message_size" : maximum size of a

single message in bytes

"service_start_timeout" : milliseconds

(thousandths) until a started service has to connect

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"auth_timeout" : milliseconds

(thousandths) a connection is given to authenticate

"max_completed_connections" : maximum number of

authenticated connections

"max_incomplete_connections" : maximum number of

unauthenticated connections

"max_connections_per_user" : maximum number of

completed connections from the same user

"max_pending_service_starts" : maximum number of

service launches in progress at the same time

"max_names_per_connection" : maximum number of

names a single connection can own

"max_match_rules_per_connection" : maximum number of

match rules for a single connection

"max_replies_per_connection" : maximum number of

pending method replies per connection (number

of calls-in-progress)

"reply_timeout" : milliseconds

(thousandths) until a method call times out

The maximum incoming/outgoing queue sizes allow a new mes-

sage to be queued if one byte remains below the maximum. So

you can in fact exceed the maximum 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. The element defines a security policy to be applied to a particular set of connections to the bus. A policy is

made up of and elements. Policies are nor-

mally used with the systemwide bus; they are analogous to a firewall in that they allow expected traffic and prevent unexpected traffic.

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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 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 element has one of four attributes: +o context="(default|mandatory)"

+o at_console="(true|false)"

+o user="username or userid" +o group="group name or gid" Policies are applied to a connection as follows: +o all context="default" policies are applied +o all group="connection's user's group" policies are applied in undefined order +o all user="connection's auth user" policies are applied in undefined order

+o all at_console="true" policies are applied

+o all at_console="false" policies are applied

+o 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. and

A element appears below a element and prohi-

bits some action. The element makes an exception to previous statements, and works just like 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"

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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:

The 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 mes-

sage header.

"Eavesdropping" occurs when an application receives a mes-

sage 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 sig-

nals). For , 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 , eavesdrop="true" indicates that the rule matches only when eavesdropping.

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eavesdrop="false" is the default for also, but here

it means that the rule applies always, even when not eaves-

dropping. The eavesdrop attribute can only be combined with

send and receive rules (with send_* and receive_* attri-

butes).

The [send|receive]_requested_reply attribute works similarly

to the eavesdrop attribute. It controls whether the or 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 , [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 , [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.*" are not allowed for now because they would be

work to implement and maybe encourage sloppy security any-

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

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 rules.

You can not 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,

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C Library Functions dbus-daemon(3)

do NOT specify ! This

will cause no-interface messages to be blocked for all ser-

vices, which is almost certainly not what you intended. Always use rules of the form:

The element contains settings related to Security Enhanced Linux. More details below. Note, SELinux is not supported on Solaris. An element appears below an element

and creates a mapping. Right now only one kind of associa-

tion is possible:

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 is currently no way to set a default for owning any name, if we add this syntax it will look like:

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 elements specify the same name, the ele-

ment appearing later in the configuration file will be used. SELinux SELinux is not supported on Solaris. 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

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C Library Functions dbus-daemon(3)

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 secu-

rity identifiers (SIDs) rather than security con-

texts. 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 indi-

cates the kind of object, e.g. a process, a regular file, a directory, a TCP socket, etc.

Access decisions specify whether or not a permis-

sion is granted for a given pair of SIDs and class.

Each object class has a set of associated permis-

sions 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 are

assuming that only UNIX domain sockets will be used to con-

nect to the systemwide bus. If this changes, we will prob-

ably 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

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C Library Functions dbus-daemon(3)

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 element described earlier in this document. If

a name has no security context associated in the configura-

tion file, the security context of the bus daemon itself will be used. DEBUGGING If you are trying to figure out where your messages are going or why you are not getting messages, there are several things you can try. Remember that the system bus is heavily locked down and if you have not installed a security policy file to allow your message through, it will not work. For the session bus, this is not a concern. The simplest way to figure out what is happening on the bus

is to run the dbus-monitor(1) program, which comes with the

D-Bus package. You can also send test messages with dbus-

send(1). 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 recom-

mended 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.)

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If you want to get fancy, you can create a custom bus confi-

guration 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.

EXAMPLES

Example 1: Message bus daemon

example% dbus-daemon

FILES The following files are used by this application:

/usr/lib/dbus-daemon

Executable for dbus-daemon

/usr/share/dbus-1/services

Directory containing standard D-Bus session services.

/usr/share/dbus-1/system-services

Directory containing standard D-Bus systemwide services.

/etc/dbus-1/session.conf

Configuration file for D-Bus session services.

/etc/dbus-1/system.conf

Configuration file for D-Bus system services.

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes:

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____________________________________________________________

| ATTRIBUTE TYPE | ATTRIBUTE VALUE |

|_____________________________|_____________________________|

| Availability | system/library/dbus |

|_____________________________|_____________________________|

| Interface stability | Volatile |

|_____________________________|_____________________________|

Manual Pages for UNIX Operating System command usage for man dbus-daemon

C Library Functions dbus-daemon(3)

NAME

dbus-daemon - Message bus daemon

SYNOPSIS

dbus-daemon [--config-file=file] [--fork | --nofork] [--

DESCRIPTION

dbus-daemon is the D-Bus message bus daemon. D-Bus is first

two applications; dbus-daemon is an application that uses

There are two standard message bus instances. dbus-daemon

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

EXTENDED DESCRIPTION

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

this would be the dbus-daemon-launch-helper executable.

dbus-daemon-launch-helper executable is not distributed with

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

C Library Functions dbus-daemon(3)

DBUS_VERBOSE=1 dbus-daemon --session --print-address

C Library Functions dbus-daemon(3)

EXAMPLES

example% dbus-daemon

/usr/lib/dbus-daemon

Executable for dbus-daemon

ATTRIBUTES

C Library Functions dbus-daemon(3)

| ATTRIBUTE TYPE | ATTRIBUTE VALUE |

SEE ALSO