#  SPDX-License-Identifier: LGPL-2.1-or-later
#
#  This file is part of systemd.
#
#  systemd is free software; you can redistribute it and/or modify it
#  under the terms of the GNU Lesser General Public License as published by
#  the Free Software Foundation; either version 2.1 of the License, or
#  (at your option) any later version.

[Unit]
Description=Wait for Network to be Configured
Documentation=man:systemd-networkd-wait-online.service(8)
ConditionCapability=CAP_NET_ADMIN
DefaultDependencies=no
Conflicts=shutdown.target
BindsTo=systemd-networkd.service
After=systemd-networkd.service
Before=network-online.target shutdown.target

[Service]
Type=oneshot
ExecStart=/usr/lib/systemd/systemd-networkd-wait-online
RemainAfterExit=yes

[Install]
WantedBy=network-online.target

modify the ExecStart line to blow:

ExecStart=/usr/lib/systemd/systemd-networkd-wait-online --interface=eth0