#
# cron 설정하기
#

 - 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 
 
 
         EX) 
 
         * systemA : 4mm dat 에 backup 
         * systemB : HDD 에 backup 
         * systemC : target system 
 
         -- system B 에서 작업 --- 
         # vi backup(HDD에 backup) 
 
         -> 아래와 같이 edit 
 
         echo " rsh systemChostname tar cvfb - 20 systemCdiretory | tar xvfbBp - 40 " 
                rsh systemChostname tar cvfb - 20 systemCdiretory | tar xvfbBp - 40 
 
         echo " backup job THE END 
                GOOD-BYE " 
 
         :wq! 
 
         # chmod 755 backup 
 
         # cd /var/spool/cron/crontabs 
 
         # vi root 
 
         #ident  "@(#)root       1.12    94/03/24 SMI"   /* SVr4.0 1.1.3.1       */ 
         # 
         # The root crontab should be used to perform accounting data collection. 
         # 
         # The rtc command is run to adjust the real time clock if and when 
         # daylight savings time changes. 
         # 
         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 
         0 3 * * * /backup > /dev/console 
 
         :wq!  --> 새벽 3시에 data backup 
 
         # reboot 
 
         -------------------------------------------------------------------------------- 
 
         -- system C 에서 작업 --- 
         # vi backup(DAT에 backup) 
 
         -> 아래와 같이 edit 
 
         echo " tar cvfb -  20 backupdiretory      |  rsh  systemAhostname  dd  of=/dev/rst5 obs=20b " 
                tar cvfb -  20 backupdiretory      |  rsh  systemAhostname  dd  of=/dev/rst5 obs=20b 
 
         echo " backup job THE END 
                GOOD-BYE " 
 
         :wq! 
 
         # chmod 755 backup 
 
         # cd /var/spool/cron/crontabs 
 
         # vi root 
 
         #ident  "@(#)root       1.12    94/03/24 SMI"   /* SVr4.0 1.1.3.1       */ 
         # 
         # The root crontab should be used to perform accounting data collection. 
         # 
         # The rtc command is run to adjust the real time clock if and when 
         # daylight savings time changes. 
         # 
         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 
         0 3 * * * /backup > /dev/console 
 
         :wq!  --> 새벽 3시에 data backup 
 
 
         #reboot