NetworkManager dispatcher script to start/stop a Systemd unit when a connection's status changes.

nm-systemd-dispatcher.sh

#!/bin/bash
# nm-systemd-dispatcher.sh
# Starts/stops a Systemd unit when a connection's status changes.
#
# Install this script to `/etc/NetworkManager/dispatcher.d/60-systemd.sh` and
# add the following section to your NetworkManager connection config in
# `/etc/NetworkManager/system-connections/*.nmconnection`:
#
#     [user]
#     systemd.unit=myservice.service
#     systemd.start=up
#     systemd.stop=down
#
# The `systemd.start` and `systemd.stop` options are optional and can be used
# to change what connection status yields what `systemctl` command. For
# example, by setting `systemd.start=pre-up` you can start the Systemd unit
# with the `pre-up` status instead. Next to `start` and `stop` the dispatcher
# script also supports `reload`, `restart`, `try-restart`, `kill`, `freeze`,
# and `thaw`. Remember that you need to symlink the dispatcher script to
# `/etc/NetworkManager/dispatcher.d/pre-{up,down}.d/` to use `pre` actions.
#
# Copyright (C) 2025-2026 Daniel Rudolf (<https://www.daniel-rudolf.de>)
# License: The MIT License <http://opensource.org/licenses/MIT>
#
# SPDX-License-Identifier: MIT

print_usage() {
    echo "Usage:"
    echo "  ${BASH_SOURCE[0]} <interface> <action>"
}

[ $# -ge 2 ] || { print_usage >&2; exit 1; }

INTERFACE="$1"
ACTION="$2"

[ -n "$INTERFACE" ] && [ -n "$ACTION" ] || exit 0
[ -n "${CONNECTION_USER_SYSTEMD__UNIT:-}" ] || exit 0

case "$ACTION" in
    "${CONNECTION_USER_SYSTEMD__START:-up}")
        systemctl start "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;

    "${CONNECTION_USER_SYSTEMD__STOP:-down}")
        systemctl stop "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;

    "${CONNECTION_USER_SYSTEMD__RELOAD:-}")
        systemctl reload "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;

    "${CONNECTION_USER_SYSTEMD__RESTART:-}")
        systemctl restart "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;

    "${CONNECTION_USER_SYSTEMD__TRY_055RESTART:-}")
        systemctl try-restart "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;

    "${CONNECTION_USER_SYSTEMD__KILL:-}")
        systemctl kill "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;

    "${CONNECTION_USER_SYSTEMD__FREEZE:-}")
        systemctl freeze "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;

    "${CONNECTION_USER_SYSTEMD__THAW:-}")
        systemctl thaw "$CONNECTION_USER_SYSTEMD__UNIT"
        ;;
esac