systemd A monkey with a typewriter Zbigniew Jędrzejewski-Szmek zbyszek@in.waw.pl busctl 1 busctl Introspect the bus busctl OPTIONS COMMAND NAME busctl may be used to introspect and monitor the D-Bus bus. 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 endpoints, show a column containing the names of containers they belong to. See systemd-machined.service8. --unique When showing the list of endpoints, 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 endpoints, show only endpoints 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. --no-legend Do not print the legend, i.e. the column headers and the footer. --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. --quiet When used with the call command suppresses display of the response message. --verbose When used with the call or get-property command shows output in a more verbose format. The following commands are understood: list Show service names on the bus. This is the default if no command is specified. status SERVICE Show process information and credentials of a bus service. monitor SERVICE Dump messages being exchanged. If SERVICE is specified, show messages to or from this endpoint. Otherwise, show all messages on the bus. Use Ctrl-C to terminate dump. capture SERVICE Similar to monitor but writes the output in pcap format (for details see the Libpcap File Format description. Make sure to redirect the output to STDOUT to a file. Tools like wireshark1 may be used to dissect and view the generated 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 Show interfaces, methods, properties and signals of the specified object (identified by its path) on the specified service. 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. 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 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. 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, 1; negative boolean values may be specified as false, no, off, 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 32bit 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. 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" 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"; }; The following command invokes a 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 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" dbus-daemon1, D-Bus, kdbus, sd-bus3, systemd1, systemd-bus-proxyd8, machinectl1, wireshark1