This is a simple script is a bit of a hack best called from /etc/rc.local on a Raspberry Pi (or other Debian based distro) during startup. It works around the fact that the Pi does not have an on-board real-time clock and ensures that network services come up after the network stack is stable.

#!/bin/bash
#
# daemon-startup-watchdog.sh - a script to work around Raspberry Pi limits
#
# Copyright (c) 2015 Gabriel M. O'Brien
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# THE SOFTWARE.
#
 
until fping -qc 3 8.8.8.8 > /dev/null 2>&1; do
  echo "Waiting for network..."
done
 
# set time from NTP server to work around lack of RTC on Pi
ntpservers=`grep '^server' /etc/ntp.conf | awk '{ print $2 }'`
 
echo "Forcing restart of ntp and setting RTC time"
service ntp stop
 
# check all servers in config until one returns valid data
for s in $ntpservers; do
  ntpdate -s $s
  [ "$?" -eq "0" ] && break
done
 
service ntp start
 
# restart other daemons
for daemon in isc-dhcp-server bind9; do
  echo "Forcing restart of $daemon"
  service $daemon restart
done