Job Scheduling Command

 crontab -e     //create & edit the crontab jobs

1st * set to minutes 0-59
2nd * set to hour 0-23
3rd * set to day of month 1-31
4th * set to month 1-12
5th * set to day of week 0-6

*/1 * * * * /root/backup.sh     //Run Cron Job Every 1 Minutes
30 * * * * /root/backup.sh     //Run Cron Job Every 30 Minutes
0 4 * * 1-5 /root/backup.sh     //run cron job monday to friday
0 4 * * 1,5 /root/backup.sh     //run cron job monday and friday only

crontab -l     //list all crontab jobs
crontab -r     //remove all jobs