系统维护常用脚本

在linux系统维护过程中，经常需要解决各种各样的需求，最简单的方式还是用linux系统本身的shell，最简单有效

这个网站很好推荐给大家点这里

１.释放内存:

cat monitor_mem.sh
#!/bin/bash

used=`free -m | awk 'NR==2' | awk '{print $3}'`
free=`free -m | awk 'NR==2' | awk '{print $4}'`

echo " date:`date +%Y%m%d%H%M` ===========================" > /var/log/mem.log
date >> /var/log/mem.log
echo "Memory usage | [Use：${used}MB][Free：${free}MB]" >> /var/log/mem.log

if [ $free -le 4000 ] ; 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" >> /var/log/mem.log
        mail -s "`hostname` mem monitor info" 15001027302@139.com < /var/log/mem.log
else
        echo "Not required" >> /var/log/mem.log
fi
exit

2,列数据转为行

cat test.txt

192.168.5.44
192.168.5.45
192.168.5.46
192.168.5.47
192.168.5.51
192.168.5.52
192.168.5.54
192.168.5.55


sed ':a;$!N;s/
/,/;ta' test.txt 
192.168.5.44,192.168.5.45,192.168.5.46,192.168.5.47,192.168.5.51,192.168.5.52,192.168.5.54,192.168.5.55

3,获取进程运行的时间

cat ./get_process_time.sh
#!/bin/bash
function show_elapsed_time()
{
    user_hz=$(getconf CLK_TCK) #mostly it's 100 on x86/x86_64
    pid=$1
    jiffies=$(cat /proc/$pid/stat | cut -d" " -f22)
    sys_uptime=$(cat /proc/uptime | cut -d" " -f1)
    last_time=$(( ${sys_uptime%.*} - $jiffies/$user_hz ))
    echo "the process $pid lasts for $last_time seconds."
}

if [ $# -ge 1 ];then
    for pid in $@
    do
        show_elapsed_time $pid
    done
fi

while read pid
do
    show_elapsed_time $pid
done

执行示例：

./get_process_time.sh 4260

4,获取进程运行的时间并杀死过期进程，以免占用内存及swap空间

cat ./get_process_time.sh
#!/bin/bash

#set -x
function show_elapsed_time()
{
    user_hz=$(getconf CLK_TCK) #mostly it's 100 on x86/x86_64
    pid=$1
    oneday=86400
    jiffies=$(cat /proc/$pid/stat | cut -d" " -f22)
    sys_uptime=$(cat /proc/uptime | cut -d" " -f1)
    last_time=$(( ${sys_uptime%.*} - $jiffies/$user_hz ))
    if [ $last_time -gt $oneday ];then
        echo "the process $pid lasts for $last_time seconds."
    kill -9 $pid
    else
    echo "no exits gt $oneday process"
    fi
}

if [ $# -ge 1 ];then
    for pid in $@
    do
        show_elapsed_time $pid
    done
fi

执行示例：
./get_process_time.sh `ps aux | grep java| grep -v grep |awk '{print $2}'|sed ':a;$!N;s/
/ /;ta'`