cubian-ntpdate

#! /bin/bash
set -e

# Warning:
# this program is designed to be executed by at command,
# don't use STDOUT in the program
# STDOUT,STDERROR will be mailed to /var/mail/

LOCKFILE=/var/lock/cubian-ntpdate.lock
SUCCESS_LOCKFILE=/var/lock/cubian-ntpdate-success.lock
DELAY=${1:-0}
MAX_AVG=0.8


# definition of some helper functions

log(){
  logger -t "networktime" "$1"
}

get_loadavg(){
  cat /proc/loadavg | awk '{print $1}'
}

do_ntpdate(){
  log "start probe interfaces"
  for interface in $(ls /sys/class/net/ | grep -v 'lo\|tunl[0-9][0-9]*\|gre[0-9][0-9]*\|ip6tnl[0-9][0-9]*\|sit[0-9][0-9]*\|p2p[0-9][0-9]*');do
      hasNetWork=$(cat /sys/class/net/$interface/carrier 2>/dev/null)
      if [[ "$hasNetWork" = "1" ]];then
          log "network interface $interface online"
          break
      else
          log "network interface $interface offline"
      fi
  done
  log "Waiting IP address for 20 seconds"
  sleep 20
  if [ "x`/usr/lib/cubian/cubian-getip`" = "x" ];then
  	log "No IPv4 address available"
  	rm $LOCKFILE
  	log "Quit"
  	exit 0
  fi
  if [[ "$hasNetWork" = "1" ]];then
  	avg=$(get_loadavg)
  	if expr $avg \< $MAX_AVG > /dev/null;then
  		ntpdateLog=$(/usr/sbin/ntpdate-debian 2>&1)
  		ret="$?"
  		echo $ntpdateLog | logger -t "networktime"
  		if [ "$ret" = "0" ];then
      	    log "success"
  			touch $SUCCESS_LOCKFILE
  		else
      	    log "fail, ntpdate error, see log, process deferred"
  		fi
  	else
      	log "system is busy, current $avg maximium $MAX_AVG, process deferred"
  	fi
  else
      log "fail, no network connection, process deferred"
  fi
}


## core logic of this script

# check for already running instance
if [ -f $LOCKFILE ];then
	exit 0
fi

# check for installed ntpd
if [ -f /etc/init.d/ntp ];then
	exit 0
fi

echo $$ > $LOCKFILE
sleep 1
[ "x$(cat $LOCKFILE)" == "x"$$ ] || exit

if [ -f $SUCCESS_LOCKFILE ];then
	log "already update time, quit automatically"
fi

log "wait interfaces ready"

while true;do
	DELAY=$(expr $DELAY \* 2)
	log "wait $DELAY seconds"
	sleep $DELAY
	set +e
	log "execute ntpdate"
	do_ntpdate
	set -e
	if [ -f $SUCCESS_LOCKFILE ];then
		break
	fi
done
rm $LOCKFILE
log "Quit"
exit 0