BUSCTL(1) busctl BUSCTL(1)
NAME
busctl - Introspect the bus
SYNOPSIS
busctl [OPTIONS...] [COMMAND] [NAME...]
DESCRIPTION
busctl may be used to introspect and monitor the D-Bus bus.
COMMANDS
The following commands are understood:
list
Show all peers on the bus, by their service names. By default,
shows both unique and well-known names, but this may be changed
with the --unique and --acquired switches. This is the default
operation if no command is specified.
Added in version 209.
status [SERVICE]
Show process information and credentials of a bus service (if one
is specified by its unique or well-known name), a process (if one
is specified by its numeric PID), or the owner of the bus (if no
parameter is specified).
Added in version 209.
monitor [SERVICE...]
Dump messages being exchanged. If SERVICE is specified, show
messages to or from this peer, identified by its well-known or
unique name. Otherwise, show all messages on the bus. Use Ctrl+C to
terminate the dump.
Added in version 209.
capture [SERVICE...]
Similar to monitor but writes the output in pcapng format (for
details, see PCAP Next Generation (pcapng) Capture File Format[1]).
Make sure to redirect standard output to a file or pipe. Tools like
wireshark(1) may be used to dissect and view the resulting files.
Added in version 218.
tree [SERVICE...]
Shows an object tree of one or more services. If SERVICE is
specified, show object tree of the specified services only.
Otherwise, show all object trees of all services on the bus that
acquired at least one well-known name.
Added in version 218.
introspect SERVICE OBJECT [INTERFACE]
Show interfaces, methods, properties and signals of the specified
object (identified by its path) on the specified service. If the
interface argument is passed, the output is limited to members of
the specified interface.
Added in version 218.
call SERVICE OBJECT INTERFACE METHOD [SIGNATURE [ARGUMENT...]]
Invoke a method and show the response. Takes a service name, object
path, interface name and method name. If parameters shall be passed
to the method call, a signature string is required, followed by the
arguments, individually formatted as strings. For details on the
formatting used, see below. To suppress output of the returned
data, use the --quiet option.
Added in version 218.
emit OBJECT INTERFACE SIGNAL [SIGNATURE [ARGUMENT...]]
Emit a signal. Takes an object path, interface name and method
name. If parameters shall be passed, a signature string is
required, followed by the arguments, individually formatted as
strings. For details on the formatting used, see below. To specify
the destination of the signal, use the --destination= option.
Added in version 242.
wait [SERVICE] OBJECT INTERFACE SIGNAL
Wait for a signal. Takes an object path, interface name, and signal
name. To suppress output of the returned data, use the --quiet
option. The service name may be omitted, in which case busctl will
match signals from any sender.
Added in version 257.
get-property SERVICE OBJECT INTERFACE PROPERTY...
Retrieve the current value of one or more object properties. Takes
a service name, object path, interface name and property name.
Multiple properties may be specified at once, in which case their
values will be shown one after the other, separated by newlines.
The output is, by default, in terse format. Use --verbose for a
more elaborate output format.
Added in version 218.
set-property SERVICE OBJECT INTERFACE PROPERTY SIGNATURE ARGUMENT...
Set the current value of an object property. Takes a service name,
object path, interface name, property name, property signature,
followed by a list of parameters formatted as strings.
Added in version 218.
help
Show command syntax help.
Added in version 209.
OPTIONS
The following options are understood:
--address=ADDRESS
Connect to the bus specified by ADDRESS instead of using suitable
defaults for either the system or user bus (see --system and --user
options).
Added in version 209.
--show-machine
When showing the list of peers, show a column containing the names
of containers they belong to. See systemd-machined.service(8).
Added in version 209.
--unique
When showing the list of peers, show only "unique" names (of the
form ":number.number").
Added in version 209.
--acquired
The opposite of --unique — only "well-known" names will be shown.
Added in version 209.
--activatable
When showing the list of peers, show only peers which have actually
not been activated yet, but may be started automatically if
accessed.
Added in version 209.
--match=MATCH
When showing messages being exchanged, show only the subset
matching MATCH. See sd_bus_add_match(3).
Added in version 209.
--size=
When used with the capture command, specifies the maximum bus
message size to capture ("snaplen"). Defaults to 4096 bytes.
Added in version 218.
--list
When used with the tree command, shows a flat list of object paths
instead of a tree.
Added in version 218.
-q, --quiet
When used with the call command, suppresses display of the response
message payload. Note that even if this option is specified, errors
returned will still be printed and the tool will indicate success
or failure with the process exit code.
Added in version 218.
--verbose
When used with the call or get-property command, shows output in a
more verbose format.
Added in version 218.
--xml-interface
When used with the introspect call, dump the XML description
received from the D-Bus
org.freedesktop.DBus.Introspectable.Introspect call instead of the
normal output.
Added in version 243.
--expect-reply=BOOL
When used with the call command, specifies whether busctl shall
wait for completion of the method call, output the returned method
response data, and return success or failure via the process exit
code. If this is set to "no", the method call will be issued but no
response is expected, the tool terminates immediately, and thus no
response can be shown, and no success or failure is returned via
the exit code. To only suppress output of the reply message
payload, use --quiet above. Defaults to "yes".
Added in version 218.
--auto-start=BOOL
When used with the call or emit command, specifies whether the
method call should implicitly activate the called service, should
it not be running yet but is configured to be auto-started.
Defaults to "yes".
Added in version 218.
--allow-interactive-authorization=BOOL
When used with the call command, specifies whether the services may
enforce interactive authorization while executing the operation, if
the security policy is configured for this. Defaults to "yes".
Added in version 218.
--timeout=SECS
When used with the call command, specifies the maximum time to wait
for method call completion. When used with the monitor command,
since version v257, specifies the maximum time to wait for messages
before automatically exiting. If no time unit is specified, assumes
seconds. The usual other units are understood, too (ms, us, s, min,
h, d, w, month, y). Note that this timeout does not apply if
--expect-reply=no is used, when combined with the call command, as
the tool does not wait for any reply message then. When not
specified or when set to 0, the default of "25s" is assumed for the
call command, and it is disabled for the monitor command.
Added in version 218.
--limit-messages=NUMBER, -N NUMBER
When used with the monitor command, if enabled will make busctl
exit when the specified number of messages have been received and
printed. This is useful in combination with --match=, to wait for
the specified number of occurrences of specific D-Bus messages.
Added in version 257.
--augment-creds=BOOL
Controls whether credential data reported by list or status shall
be augmented with data from /proc/. When this is turned on, the
data shown is possibly inconsistent, as the data read from /proc/
might be more recent than the rest of the credential information.
Defaults to "yes".
Added in version 218.
--watch-bind=BOOL
Controls whether to wait for the specified AF_UNIX bus socket to
appear in the file system before connecting to it. Defaults to off.
When enabled, the tool will watch the file system until the socket
is created and then connect to it.
Added in version 237.
--destination=SERVICE
Takes a service name. When used with the emit command, a signal is
emitted to the specified service.
Added in version 242.
--user
Talk to the service manager of the calling user, rather than the
service manager of the system.
--system
Talk to the service manager of the system. This is the implied
default.
-H, --host=
Execute the operation remotely. Specify a hostname, or a username
and hostname separated by "@", to connect to. The hostname may
optionally be suffixed by a port ssh is listening on, separated by
":", and then a container name, separated by "/", which connects
directly to a specific container on the specified host. This will
use SSH to talk to the remote machine manager instance. Container
names may be enumerated with machinectl -H HOST. Put IPv6 addresses
in brackets.
-M, --machine=
Execute operation on a local container. Specify a container name to
connect to, optionally prefixed by a user name to connect as and a
separating "@" character. If the special string ".host" is used in
place of the container name, a connection to the local system is
made (which is useful to connect to a specific user's user bus:
"--user --machine=lennart@.host"). If the "@" syntax is not used,
the connection is made as root user. If the "@" syntax is used
either the left hand side or the right hand side may be omitted
(but not both) in which case the local user name and ".host" are
implied.
-C, --capsule=
Execute operation on a capsule. Specify a capsule name to connect
to. See capsule@.service(5) for details about capsules.
Added in version 256.
-l, --full
Do not ellipsize the output in list command.
Added in version 245.
--json=MODE
Shows output formatted as JSON. Expects one of "short" (for the
shortest possible output without any redundant whitespace or line
breaks), "pretty" (for a pretty version of the same, with
indentation and line breaks) or "off" (to turn off JSON output, the
default).
-j
Equivalent to --json=pretty if running on a terminal, and
--json=short otherwise.
--no-pager
Do not pipe output into a pager.
--no-legend
Do not print the legend, i.e. column headers and the footer with
hints.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
PARAMETER FORMATTING
The call and set-property commands take a signature string followed by
a list of parameters formatted as string (for details on D-Bus
signature strings, see the Type system chapter of the D-Bus
specification[2]). For simple types, each parameter following the
signature should simply be the parameter's value formatted as string.
Positive boolean values may be formatted as "true", "yes", "on", or
"1"; negative boolean values may be specified as "false", "no", "off",
or "0". For arrays, a numeric argument for the number of entries
followed by the entries shall be specified. For variants, the signature
of the contents shall be specified, followed by the contents. For
dictionaries and structs, the contents of them shall be directly
specified.
For example,
s jawoll
is the formatting of a single string "jawoll".
as 3 hello world foobar
is the formatting of a string array with three entries, "hello",
"world" and "foobar".
a{sv} 3 One s Eins Two u 2 Yes b true
is the formatting of a dictionary array that maps strings to variants,
consisting of three entries. The string "One" is assigned the string
"Eins". The string "Two" is assigned the 32-bit unsigned integer 2. The
string "Yes" is assigned a positive boolean.
Note that the call, get-property, introspect commands will also
generate output in this format for the returned data. Since this format
is sometimes too terse to be easily understood, the call and
get-property commands may generate a more verbose, multi-line output
when passed the --verbose option.
EXAMPLES
Example 1. Write and Read a Property
The following two commands first write a property and then read it
back. The property is found on the "/org/freedesktop/systemd1" object
of the "org.freedesktop.systemd1" service. The name of the property is
"LogLevel" on the "org.freedesktop.systemd1.Manager" interface. The
property contains a single string:
# busctl set-property org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager LogLevel s debug
# busctl get-property org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager LogLevel
s "debug"
Example 2. Terse and Verbose Output
The following two commands read a property that contains an array of
strings, and first show it in terse format, followed by verbose format:
$ busctl get-property org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager Environment
as 2 "LANG=en_US.UTF-8" "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin"
$ busctl get-property --verbose org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager Environment
ARRAY "s" {
STRING "LANG=en_US.UTF-8";
STRING "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin";
};
Example 3. Invoking a Method
The following command invokes the "StartUnit" method on the
"org.freedesktop.systemd1.Manager" interface of the
"/org/freedesktop/systemd1" object of the "org.freedesktop.systemd1"
service, and passes it two strings "cups.service" and "replace". As a
result of the method call, a single object path parameter is received
and shown:
# busctl call org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager StartUnit ss "cups.service" "replace"
o "/org/freedesktop/systemd1/job/42684"
SEE ALSO
dbus-daemon(1), D-Bus[3], sd-bus(3), varlinkctl(1), systemd(1),
machinectl(1), wireshark(1)
NOTES
1. PCAP Next Generation (pcapng) Capture File Format
https://github.com/pcapng/pcapng/
2. Type system chapter of the D-Bus specification
https://dbus.freedesktop.org/doc/dbus-specification.html#type-
system
3. D-Bus
https://www.freedesktop.org/wiki/Software/dbus
systemd 258 BUSCTL(1)
busctl \- Introspect the bus