osi-tools/Documentation/module-examples/systemd-dhcpcd.sh

#!/hint/bash -euE
# Copyright (C) 2018  Luke Shumaker
# SPDX-License-Identifier: AGPL-3.0-or-later

# Also enable haveged.  Without it, TLS will be unavailable for a
# while even after network-online.target because getrandom(2) will
# block for so long that the connection will time out.

packages+=('haveged')

post_install+=(10:dhcpcd:post_install)
dhcpcd:post_install() {
	local arg_mountpoint=$1

	cat <<-'EOT' > "${arg_mountpoint}/etc/udev/rules.d/81-dhcpcd.rules"
		ACTION=="add", SUBSYSTEM=="net", ENV{SYSTEMD_WANTS}="dhcpcd@$name.service"
		EOT
	mkdir "${arg_mountpoint}/etc/systemd/system/dhcpcd@.service.d"
	cat <<-'EOT' > "${arg_mountpoint}/etc/systemd/system/dhcpcd@.service.d/wait-online.conf"
		[Unit]
		Before=network-online.target
		EOT
	mkdir "${arg_mountpoint}/etc/systemd/system/network-online.target.d"
	cat <<-'EOT' > "${arg_mountpoint}/etc/systemd/system/network-online.target.d/udev-settle.conf"
		[Unit]
		Wants=systemd-udev-settle.service
		After=systemd-udev-settle.service
		EOT

	systemctl --root="$arg_mountpoint" enable haveged.service
}