Fix resolv.conf being wiped by dhcpcd on first reboot.

Wait for network-online, drop DHCP while still dhcp so dhcpcd exits
before writing static resolv.conf. Do not touch dhcpcd.conf.

postinstall/init.sh

@@ -1,8 +1,5 @@
 #!/usr/bin/env bash
 
-# Sometimes the network is slow, wait a bit
-sleep 10
-
 # Get the current DHCP network address, gateway and DNS servers
 NIC=$(ip link | grep "^2:" | awk '{print $2}' | tr -d ":")
 IP_ADDRESS=$(ip address show ${NIC} | grep -E "inet " | awk '{print $2}')
@@ -11,6 +8,10 @@ IP_ADDRESS=$(echo ${IP_ADDRESS} | sed 's/\/.*//')
 GATEWAY=$(ip route | grep "default" | awk '{print $3}')
 DNS_SERVERS=$(awk '/^nameserver/ {print $2}' /etc/resolv.conf | xargs)
 
+# Tear down DHCP first, while interfaces is still dhcp, so dhcpcd is gone
+# before we write a static resolv.conf (otherwise it rewrites it on exit)
+ifdown "${NIC}" || true
+
 # Network interfaces (static address)
 cat << EOF > /etc/network/interfaces
 auto lo
@@ -25,7 +26,10 @@ EOF
 
 # Tabs instead of spaces, neat the file
 sed -i 's/  /\t/gm' /etc/network/interfaces
-# write a static resolv.conf
+
+ifup "${NIC}" || true
+
+# write a static resolv.conf after dhcpcd is gone so it survives reboot
 rm -f /etc/resolv.conf
 for ns in ${DNS_SERVERS}; do
   echo "nameserver ${ns}" >> /etc/resolv.conf