Problem med Cronjob / MRTG

Jeg har sat en maskine op med SME Server 5.6 og MRTG
Jeg kan fint få MRTG til at virke men det kniber en del med at få den til at opdatere hver 5. min.
Nu skal jeg manuelt skrive "/usr/bin/mrtg /etc/mrtg/mrtg.cfg" før den henter data fra routeren og laver en graf.. Så derfor skulle jeg mene at den er gal med cronjob.. lige nu ser /etc/crontab/ sådan her ud:

#------------------------------------------------------------
# DO NOT MODIFY THIS FILE! It is updated automatically by the
# SME Server software. Instead, modify the source template in
# an /etc/e-smith/templates-custom directory. For more
# information, see http://www.e-smith.org/custom/
#
# copyright (C) 2002 Mitel Networks Corporation
#------------------------------------------------------------

#------------------------------------------------------------
# DO NOT MODIFY THIS FILE! It is updated automatically by the
# e-smith server and gateway software. Instead, modify the source
# template in the /etc/e-smith/templates directory. For more
# information, see http://www.e-smith.org.
#
# copyright (C) 2001 Mitel Networks Corporation
#------------------------------------------------------------

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root

# run-parts
01 * * * * root run-parts /etc/cron.hourly
02 4 * * * root run-parts /etc/cron.daily
22 4 * * 0 root run-parts /etc/cron.weekly
42 4 1 * * root run-parts /etc/cron.monthly

12 1 */7 * * root    /sbin/e-smith/signal-event logrotate

5 * * * * /usr/bin/mrtg /etc/mrtg/mrtg.cfg



#------------------------------------------------------------
# TEMPLATE END
#------------------------------------------------------------