아래 코드를 응용하여 cron에 등록하면 됩니다.
#!/bin/sh
cd /media/backupHDD/mysql_backup/
time=`date +%Y%m%d%H%M`
mysqldump -root -ppassword crmdb > $time".sql"
WEEKAGO=`date -d "7 days ago" +%Y%m%d`
rm /media/backupHDD/mysql_backup/$WEEKAGO*.sql
crontab -l
00 08 * * * /media/backupHDD/mysql_backup/dbbackup.sh
30 12 * * * /media/backupHDD/mysql_backup/dbbackup.sh
00 20 * * * /media/backupHDD/mysql_backup/dbbackup.sh