How to start a never ending script at startup

I'm trying to automatically run a never ending script (so it doesn't return 0 on exit) at startup on my headless ubuntu 12.04 server with no GUI.

I have tried @reboot nohup /home/luke/netup.sh & in crontab and the script doesn't work properly although it appears to run.
I have tried update-rc.d netup.sh defaults, the script started but still didn't run properly and most of the other programs that are supposed to auto start didn't start.

The script attempts to monitor and record internet outages and contains a while-do loop. It works when logged in to the server and started manually.

Here is the script

#!/bin/bash
#
# Script to monitor internet up time
echo "Server started"  `date "+%F  %T"`  >> /home/luke/netup.log
START=0
while [ 1 ] ; do                    # continuous loop
#------------------------------------------------------------------------
/bin/ping -q 8.8.8.8 -c1 1>/dev/null 2>/dev/null # ping test
PING=$?
#------------------------------------------------------------------------
if [ $PING = 0 ]; then              # ping success
    if [ $START -ne 0 ]; then       # was down
        END=$(date +%s)
        TIME=$(($END - $START))
        START=0
        let TIME=($TIME/60)     #convert seconds to minutes
        echo "Failed" $FAIL_TIME "for" $TIME "minutes" >> /home/luke/netup.log
    fi
else                        # ping failure
    if [ $START -eq 0 ]; then       # was up
        START=$(date +%s)
        FAIL_TIME=$(date "+%F  %T")
    fi
fi
#------------------------------------------------------------------------
if [ $PING = 0 ]; then              # wait
    sleep 60
else
    sleep 10
fi
done

Rather than setting up a script to run constantly at startup, why not change it to run using cron? Since you are telling it to sleep for 60 seconds between runs anyway, using cron to run a script without a while loop once a minute would make more sense and be simpler to manage.

You might also be interested in the answers for this question on serverfault:

https://serverfault.com/questions/49082/can-i-run-a-cron-job-more-frequently-than-every-minute