定時釋放Linux/CentOS緩存的腳本(yl_dropcaches)如下:
#!/bin/bash
used=`free -m | awk 'NR==2' | awk '{print $3}'`
free=`free -m | awk 'NR==2' | awk '{print $4}'`
echo "===========================" >> yl_dropcaches.log
date >> yl_dropcaches.log
echo "Memory usage | [Use:${used}MB][Free:${free}MB]" >> yl_dropcaches.log
# drop caches when the free memory less than 10G
if [ $free -le 10000 ] ; then
#sync && echo 1 > /proc/sys/vm/drop_caches
#sync && echo 2 > /proc/sys/vm/drop_caches
sync && echo 3 > /proc/sys/vm/drop_caches
echo "OK" >> yl_dropcaches.log
else
echo "Not required" >> yl_dropcaches.log
fi
#!/bin/bash
used=`free -m | awk 'NR==2' | awk '{print $3}'`
free=`free -m | awk 'NR==2' | awk '{print $4}'`
echo "===========================" >> yl_dropcaches.log
date >> yl_dropcaches.log
echo "Memory usage | [Use:${used}MB][Free:${free}MB]" >> yl_dropcaches.log
# drop caches when the free memory less than 10G
if [ $free -le 10000 ] ; then
#sync && echo 1 > /proc/sys/vm/drop_caches
#sync && echo 2 > /proc/sys/vm/drop_caches
sync && echo 3 > /proc/sys/vm/drop_caches
echo "OK" >> yl_dropcaches.log
else
echo "Not required" >> yl_dropcaches.log
fi
改為可執行(chmod +xyl_dropcaches)後,将其加入定時任務中:
echo '*/30 * * * * sh /home/yl_dropcaches' >> /var/spool/cron/root
echo '*/30 * * * * sh /home/yl_dropcaches' >> /var/spool/cron/root
然後,重新開機一下即可(service crond restart)。
CentOS預設會将crontab設定為開啟的狀态; 可檢視其狀态或開啟:service crond status/start/stop/restart/reload 可以用以下指令來操作crontab: crontab -l#檢視List crontab -e #編輯Edit crontab -r #删除Remove crontab的規則(cat /etc/crontab)如下:
# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executed
# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executed
從左至右,每個*分别代表:分,時,日,月,周;最後為要執行的指令;
其中* / - , 這些通配符的含義為:
* 表示所有數值,如第一位使用* 表示每分鐘
/ 表示每,如第一位使用 */5 表示每5分鐘
- 表示數值範圍,如第二位使用2-4表示2點到4點
, 表示離散的多個數值,如第2位使用6,8 表示6點和8點
指定"步長":8-14/2 表示8,10,12,14
指定清單:比如 "1,2,3,4″,"0-4,8-12″