using systemd-networkd on beaglebone

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## THIS IS NOT A SCRIPT, IT'S A SEQUENCE OF STEPS TO BE PERFORMED MANUALLY ##
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##                            READ THE COMMENTS                            ##
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# replacing entire networking setup (connman + ifupdown + boot scripts) on
# beagleboard.org images by systemd-networkd.
#
# for usb networking I'm using purely g_ether, though you're free to set up
# a composite gadget like the default config does
#
# TODO test the usb networking
# TODO wifi

cat >/etc/systemd/network/eth0.network  <<__END__
[Match]
Name=eth0

[Network]
DHCP=ipv4

[DHCP]
UseDomains=yes
__END__

cat >/etc/systemd/network/usb0.network <<__END__
[Match]
Name=usb0

[Link]
RequiredForOnline=no

[Network]
DHCP=no
Address=192.168.7.2/24
DHCPServer=on

[DHCPServer]
EmitDNS=no
EmitRouter=no
EmitTimezone=no
# compat with usb networking config on default image:
MaxLeaseTimeSec=2min
PoolSize=1
__END__

cat >/etc/modules-load.d/gadget.conf <<__END__
g_ether
__END__

systemctl enable systemd-networkd systemd-resolved
systemctl disable bb-bbai-tether bb-wl18xx-wlan0 connman dnsmasq hostapd networking udhcpd wpa_supplicant generic-board-startup
reboot


# after reboot:

apt purge connman ifupdown isc-dhcp-client isc-dhcp-common udhcpd
# XXX can't remove dnsmasq on bbai since bb-bbai-firmware rudely depends on it


# fixing /etc/resolv.conf before reboot won't work since connman will fight you
ln -sfT /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
# fallback for debian stretch:
[[ -f /etc/resolv.conf ]] || ln -sfT /lib/systemd/resolv.conf /etc/resolv.conf