Pb rrdtool

Bonjour,
j'ai programmé des script pour la création d'un graphe pour le ping.voici le contenu des scripts:
//create.sh
#!/bin/bash

RRDTOOL='/usr/bin/rrdtool'
FILE='/var/www/pinggraph/ping.rrd'
HOST='localhost'
OUTPUT='/var/www/pinggraph/ping.png'

$RRDTOOL create $FILE -s 60 \
DS:ping:GAUGE:120:0:65535 \
RRA:AVERAGE:0.5:1:2880

UPDATECMD=$(ping -c 3 -w 6 $HOST | grep rtt | awk -F "/" '{ print $5 }' )

$RRDTOOL update $FILE N:$UPDATECMD

//graphe.sh
#!/bin/bash

RRDTOOL='/usr/bin/rrdtool'
FILE='/var/www/pinggraph/ping.rrd'
HOST='localhost'
OUTPUT='/var/www/pinggraph/ping.png'

$RRDTOOL graph $OUTPUT \
-t "WAN Ping" -v "Time in ms" \
--start="now-1d" \
--end="now" \
--height="120" \
--width="440" \
-c "BACK#000000" \
-c "SHADEA#000000" \
-c "SHADEB#000000" \
-c "FONT#DDDDDD" \
-c "CANVAS#202020" \
-c "GRID#666666" \
-c "MGRID#AAAAAA" \
-c "FRAME#202020" \
-c "ARROW#FFFFFF" \
"DEF:ping_time=$FILE:ping:AVERAGE" \
"CDEF:shading2=ping_time,0.98,*" "AREA:shading2#F90000:$HOST" \
"GPRINT:ping_time:LAST:Last\: %5.2lf ms" \
"GPRINT:ping_time:MIN:Min\: %5.2lf ms" \
"GPRINT:ping_time:MAX:Max\: %5.2lf ms" \
"GPRINT:ping_time:AVERAGE:Avg\: %5.2lf ms" \
"CDEF:shading10=ping_time,0.90,*" "AREA:shading10#E10000" \
"CDEF:shading15=ping_time,0.85,*" "AREA:shading15#D20000" \
"CDEF:shading20=ping_time,0.80,*" "AREA:shading20#C30000" \
"CDEF:shading25=ping_time,0.75,*" "AREA:shading25#B40000" \
"CDEF:shading30=ping_time,0.70,*" "AREA:shading30#A50000" \
"CDEF:shading35=ping_time,0.65,*" "AREA:shading35#960000" \
"CDEF:shading40=ping_time,0.60,*" "AREA:shading40#870000" \
"CDEF:shading45=ping_time,0.55,*" "AREA:shading45#780000" \
"CDEF:shading50=ping_time,0.50,*" "AREA:shading50#690000" \
"CDEF:shading55=ping_time,0.45,*" "AREA:shading55#5A0000" \
"CDEF:shading60=ping_time,0.40,*" "AREA:shading60#4B0000" \
"CDEF:shading65=ping_time,0.35,*" "AREA:shading65#3C0000" \
"CDEF:shading70=ping_time,0.30,*" "AREA:shading70#2D0000" \
"CDEF:shading75=ping_time,0.25,*" "AREA:shading75#180000" \
"CDEF:shading80=ping_time,0.20,*" "AREA:shading80#0F0000" \
"CDEF:shading85=ping_time,0.15,*" "AREA:shading85#000000" >/dev/null

lorsque j'exécute ces deux scripts (./create.sh et ./graphe.sh) un graphe est créé mais il est vide!!!
comment faire pour afficher le graphe???
merci d'avance
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