Step # 7 Create crontab entry so that mrtg graph / images get generated every 5 minutes
(a) Login as a root user or login as a mrtg user and type the following command:
# crontab -e
(b) Add mrtg cron job entry to configuration file (append following line to it):
*/5 * * * * /usr/bin/mrtg /etc/mrtg/mymrtg.cfg --logging /var/log/mrtg.log
Close and save file. You are done with MRTG configuration.See how to add jobs to cron Under Linux or UNIX for more info.