busctl

systemd

busctl

1

busctl

Introspect the bus

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.

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).

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 or limit it with the --limit-messages= option.

capture <SERVICE>
Similar to monitor but writes the output in pcapng format (for details, see PCAP Next Generation (pcapng) Capture File Format). 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.

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.

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.

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.

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.

wait <SERVICE> <OBJECT> <INTERFACE> <SIGNAL>
Wait for a signal. Takes an object path, interface name, and signal name. Use the --limit-messages= option to wait for more than just one signal before exiting. 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.

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.

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.

help
Show command syntax help.

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).

--show-machine
When showing the list of peers, show a column containing the names of containers they belong to. See systemd-machined.service(8).

--unique
When showing the list of peers, show only "unique" names (of the form :number.number).

--acquired
The opposite of --unique — only "well-known" names will be shown.

--activatable
When showing the list of peers, show only peers which have actually not been activated yet, but may be started automatically if accessed.

--match=MATCH
When showing messages being exchanged, show only the subset matching <MATCH>. See sd_bus_add_match(3).

--size=
When used with the capture command, specifies the maximum bus message size to capture ("snaplen"). Defaults to 4096 bytes.

--list
When used with the tree command, shows a flat list of object paths instead of a tree.

-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.

--verbose
When used with the call or get-property command, shows output in a more verbose format.

--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.

--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.

--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.

--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.

--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.

--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. While if not specified or is set to special value infinity, the default is to keep monitoring without limitations.

When used with the wait command, it will make busctl exit when the specified number of DBus signals have been received and printed. Setting it to special value infinity will sustain busctl to receive and print signals continuously without limitations. When nothing is specified, the default is to exit immediately after receiving and printing the first signal.

--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.

--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.

--destination=SERVICE
Takes a service name. When used with the emit command, a signal is emitted to the specified service.

-l; --full
Do not ellipsize the output in list command.

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). 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

# 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"

$ 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";
};

# 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, sd-bus(3), varlinkctl(1), systemd(1), machinectl(1), wireshark(1)