#
# cron setup
#
  
         - define : 특정시간에 backup 또는 실행시킬 명령어 auto 수행 
 
         * /usr/bin/crontab 
 
          1. cron command 
 
            - Edit the user's crontab file 
             # crontab -e 
          15 3 * * 1-5 find $HOME -name core 2>/dev/null |  xargs 
                   rm -f 
 
            - List the current crontab file 
              # crontab -l 
           0 2 * * 0,4 /etc/cron.d/logchecker 
           5 4 * * 6   /usr/lib/newsyslog 
           15 3 * * * /usr/lib/fs/nfs/nfsfind 
           1 2 * * * [ -x /usr/sbin/rtc ] && /usr/sbin/rtc -c > /dev/null 2>&1 
 
          2. Control files for cron 
 
              # /var/spool/cron/cron.allow 
              # /var/spool/cron/cron.deny 
 
           3. crontab Entry Format 
 
               minute (0-59), 
               hour (0-23), 
               day of the month (1-31), 
               month of the year (1-12), 
               day of the week (0-6 with 0=Sunday 
           15 3 * * 1-5 find $HOME -name core 2>/dev/null 
           -------------> 앞부분 부터 minute