troglobit/man
MCTL(8) System Manager's Manual (smm) MCTL(8)

mctl —
status tool for mcd(8)

mctl [
-hmptv
] [
-i NAME
] [
-u FILE
] [
COMMAND
]

mctl queries a running mcd(8) over its IPC socket and shows the queriers, the group memberships and the multicast state of the bridge. Without a command it runs show.
Most bridge state comes from the iproute2 tools ip(8) and bridge(8), and from jq(1). Their BusyBox versions are not enough, use check to confirm.

, --help
Show usage and, when mcd is running, the available commands.
, --ident=NAME
Talk to an mcd started with the same -i NAME.
, --monitor
Run the command every two seconds, like watch(1).
, --plain
Plain table headings, no terminal control characters. Implied for JSON output.
, --no-heading
Skip table headings.
, --ipc=FILE
IPC socket, default derived from the identity. Also settable with the MCD_SOCK environment variable.
, --version
Show version and exit.
Output width follows the terminal.

Commands can be abbreviated, e.g. s i for show interfaces. Adding json to a show command gives machine readable output.
[
igmp
] [
json
]
Overview: global settings, bridge port roles, the queriers and the group memberships. In JSON the queriers are split in “multicast-queriers” for IGMP and “mld-queriers” for MLD.
[
json
]
Global settings.
[
json
]
One row per interface and protocol: VLAN, protocol, elected querier, state, query interval, querier timeout and protocol version.
[
json
]
IGMP and MLD group memberships, as seen by the bridge.
[
json
]
Multicast router ports, grouped per bridge.
The bridge multicast forwarding database, as ‘bridge mdb show’ but readable.
Verify that the tools listed above are available.
Show the version of the running mcd.
List the commands the running mcd supports.

IPC socket path, overridden by -u.

/run/mcd.sock
Default IPC socket, follows the identity. The group owner is set at build time, see ‘configure --with-group’.

$ mctl show interfaces 
Interface       VID  Proto  Querier                      State  Interval  Timeout  Ver 
vlan1                IGMP   192.168.1.1                     Up       125     None    3 
vlan1                MLD    fe80::7a4c:9bff:fe12:3456       Up       125     None    2 
br0              42  IGMP   0.0.0.0                         Up       125     None    3 
br0              42  MLD    ::                              Up       125     None    2
The IPC protocol is plain text, one command per connection, so other programs can use it directly: 
echo "show igmp json" | socat - UNIX-CONNECT:/run/mcd.sock

mcd.conf(5), mcd(8)

mctl is maintained by Joachim Wiberg, Tobias Waldekranz and the KernelKit team, https://kernelkit.org. See mcd(8) for its history.
October 16, 2026 Debian

Maintained in kernelkit/mcd as man/mctl.8. Send corrections there, or read it on the mirror.