General :: How To Make Growisofs Working With Cron

I make a script to automate burning backup files on dvd. It works fine if I start it from root user, but if I start it. From cronjob do noting. I try on growisofs the option -use-the-force-luke=force but nothing happens. I check the env of cron:

HOME=/root
LOGNAME=root
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
PWD=/root
SHELL=/bin/bash
SHLVL=1
XDG_SESSION_COOKIE=3e0d70f7b71074a0b1fff4bb4aa97d13-1281297181.926502-724038309
_=/usr/bin/env
and it seems ok i've got my script in /usr/local/bin and growisofs in /usr/bin

Code of my script below:
#!/bin/bash
bkup_path='/bkrepo/';
prefix='PAR*';
totdimfile=0
for FILE in $(/bin/ls -r $bkup_path$prefix)

do
dimfile=`/bin/ls -l $FILE | /usr/bin/awk -F " " '{print $5}' `
let "totdimfile += dimfile";
if [ "$totdimfile" -lt "4700000000" ]
then
NAMEFILE=`/bin/ls -l $FILE | /usr/bin/awk -F " " '{print $8}' `
ALLNAMEFILE="$ALLNAMEFILE $NAMEFILE";
fi
done

/usr/bin/growisofs -use-the-force-luke=force -Z /dev/scd0 -R -J $ALLNAMEFILE
/usr/bin/growisofs -M /dev/scd0=/dev/zero
/usr/bin/eject
end code of my script