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syntax : crontab -u (username) {-e | -l | -r } -u : user executes crontab -e : edit crontab list -l : show contab list -r : remove crontab making crontab m  h  dom  mon  dow  command m : minute, 0 - 59, * h : hour, 0 -23, * dom : day of month, 1 - 31 mon : month, 1 - 12 dow :day of week, 0 - 6 (where 0=sunday, 1=monday) command examples : 30  *  *  * * /etc/backup.sh