一、监控本地（localhost）内存

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1、上传监控脚本 check_mem 到/usr/local/nagios/libexec

# chown -R nagios.nagios check_mem
# chmod +x check_mem

2、修改commands配置

# vim /usr/local/nagios/etc/objects/commands.cfg 
define command{
        command_name        check_mem
        command_line        $USER1$/check_mem -w $ARG1$ -c $ARG2$
        }

3、修改localhost.cfg

# vim /usr/local/nagios/etc/objects/localhost.cfg 
define service{
        use                             local-service
        host_name                       localhost
        service_description             check_mem
        check_command                   check_mem!20!10
        }

4、重启nagios服务

# service nagios restart

5、check_mem 脚本

#!/bin/bash  
USAGE="`basename $0` [-w|--warning] [-c|--critical]"
THRESHOLD_USAGE="WARNING threshold must be greater than CRITICAL: `basename $0` $*"
calc=/tmp/memcalc
percent_free=/tmp/mempercent
critical=""
warning=""
STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3
# print usage  
if [[ $# -lt 4 ]]
then
        echo ""  
        echo "Wrong Syntax: `basename $0` $*"  
        echo ""  
        echo "Usage: $USAGE"  
        echo ""  
        exit 0
fi
# read input  
while [[ $# -gt 0 ]]  
  do
        case "$1" in
               -w|--warning)
               shift
               warning=$1
        ;;
               -c|--critical)
               shift
               critical=$1
        ;;
        esac
        shift
  done

# verify input  
if [[ $warning -eq $critical || $warning -lt $critical ]]
then
        echo ""  
        echo "$THRESHOLD_USAGE"  
        echo ""  
        echo "Usage: $USAGE"  
        echo ""  
        exit 0
fi
# Total memory available  
total=`free -m | head -2 |tail -1 |gawk '{print $2}'`
# Total memory used  
used=`free -m | head -2 |tail -1 |gawk '{print $3}'`
# Calc total minus used  
free=`free -m | head -2 |tail -1 |gawk '{print $2-$3}'`
# normal values  
#echo "$total"MB total  
#echo "$used"MB used  
#echo "$free"MB free  
# make it into % percent free = ((free mem / total mem) * 100)  
echo "5" > $calc # decimal accuracy  
echo "k" >> $calc # commit  
echo "100" >> $calc # multiply  
echo "$free" >> $calc # division integer  
echo "$total" >> $calc # division integer  
echo "/" >> $calc # division sign  
echo "*" >> $calc # multiplication sign  
echo "p" >> $calc # print  
percent=`/usr/bin/dc $calc|/bin/sed 's/^\./0./'|/usr/bin/tr "." " "|/usr/bin/gawk {'print $1'}`
#percent1=`/usr/bin/dc $calc`  
#echo "$percent1"  
if [[ "$percent" -le  $critical ]]
        then
                echo "CRITICAL - $free MB ($percent%) Free Memory"  
                exit 2
fi
if [[ "$percent" -le  $warning ]]
        then
                echo "WARNING - $free MB ($percent%) Free Memory"  
                exit 1
fi
if [[ "$percent" -gt  $warning ]]
        then
                echo "OK - $free MB ($percent%) Free Memory"  
                exit 0
fi

二、监控客户端内存使用情况

1、上传监控脚本 check_mem 到/usr/local/nagios/libexec

# chown -R nagios.nagios check_mem
# chmod +x check_mem

2、修改nrpe.cfg

# vim /usr/local/nagios/etc/nrpe.cfg 
command[check_users]=/usr/local/nagios/libexec/check_users -w 3 -c 5
command[check_load]=/usr/local/nagios/libexec/check_load -w 15,10,5 -c 30,25,20
command[check_xvda]=/usr/local/nagios/libexec/check_disk -w 10% -c 5% -p /dev/xvda
command[check_zombie_procs]=/usr/local/nagios/libexec/check_procs -w 5 -c 10 -s Z
command[check_total_procs]=/usr/local/nagios/libexec/check_procs -w 150 -c 200 
command[check_xvdb2]=/usr/local/nagios/libexec/check_disk -w 10% -c 5% -p /dev/xvdb2
command[check_swap]=/usr/local/nagios/libexec/check_swap -w 20% -c 10%
command[check_mem]=/usr/bin/sudo /usr/local/nagios/libexec/check_mem -w 20 -c 10   #增加此行

3、在nagios服务器端增加监控服务

# vim /usr/local/nagios/etc/servers/192.168.200.111.cfg
define service{
        use                             generic-service
        host_name                       192.168.200.111
        service_description             check_mem
        check_command                   check_nrpe!check_mem
        }

三、排错

1、NRPE: Unable to read output

（1）为nagios用户增加sudo权限

# visudo
nagios  ALL=(ALL) NOPASSWD:/usr/local/nagios/libexec/check_mem

（2）注释掉一下行，表示不需要控制终端

# visudo
#Defaults    requiretty

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四、nagios监控MySQL

1、check_mysql

    nagios监控mysql使用的是 check_mysql 这个插件，需要在nagios服务器上先安装mysql-devel，然后再重新安装nagios-plugin，这样才会出现check_mysql。否则即使copy了一份，也照样用不了。

2、编译或重新编译 nagios-plugin

#yum -y install mysql-devl
#cd nagios-plugins-2.0.3
#./configure --with-nagios-user=nagios --with-nagios-group=nagios
#make && make install

3、查看 check_mysql

# ls /usr/local/nagios/libexec/check_mysql

4、建立专用数据库

# mysql -uroot -p
mysql> create database nagios_monitor;

mysql> grant select on nagios_monitor.* to nagios@'%' identified by '123qaz!@#';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> select User,Password,Host from mysql.user;
+--------+-------------------------------------------+--------------+
| User   | Password                                  | Host         |
+--------+-------------------------------------------+--------------+
| root   | *B9627CB37815863D1E98D0C41E0233A772355E2B | localhost    |
| root   | *B9627CB37815863D1E98D0C41E0233A772355E2B | 127.0.0.1    |
| root   | *B9627CB37815863D1E98D0C41E0233A772355E2B | ::1          |
| cacti  | *BC3E1F14C7940F9C8BCDB05A38385754BB55CD64 | localhost    |
| nagios | *BC3E1F14C7940F9C8BCDB05A38385754BB55CD64 | %            |
+--------+-------------------------------------------+--------------+
8 rows in set (0.00 sec)

5、check 一下

# /usr/local/nagios/libexec/check_mysql -H 192.168.200.105 -unagios -dnagios_monitor -p 123qaz!@#
# 报了一个错
/usr/local/nagios/libexec/check_mysql: error while loading shared libraries: libmysqlclient.so.18: cannot open shared object file: No such file or directory
# 解决：
ln -sv /usr/local/mysql/lib/libmysqlclient.so.18 /usr/lib64/libmysqlclient.so.18
# 再重新测试
# /usr/local/nagios/libexec/check_mysql -H 192.168.200.111 -unagios -dnagios_monitor -p 123qaz!@#
Uptime: 13991  Threads: 5  Questions: 1242101  Slow queries: 0  Opens: 159  Flush tables: 1  Open tables: 60  Queries per second avg: 88.778|Connections=315c;;; Open_files=85;;; Open_tables=60;;; Qcache_free_memory=16285768;;; Qcache_hits=1210926c;;; Qcache_inserts=16654c;;; Qcache_lowmem_prunes=0c;;; Qcache_not_cached=2c;;; Qcache_queries_in_cache=283;;; Queries=1242101c;;; Questions=1242101c;;; Table_locks_waited=2c;;; Threads_connected=5;;; Threads_running=1;;; Uptime=13991c;;;

6、监控localhost

（1）修改 commands.cfg

# vim /usr/local/nagios/etc/objects/commands.cfg
define command{
        command_name check_mysql
        command_line $USER1$/check_mysql -H $HOSTADDRESS$ -unagios -dnagios_monitor -p123qaz!@#
}

（2）修改 localhost.cfg

# vim /usr/local/nagios/etc/objects/localhost.cfg
define service{
        use                             local-service
        host_name                       localhost
        service_description             check_mysql
        check_command                   check_mysql
        }

（3）重启 nagios

# service nagios restart

7、监控客户端

（1）check 一下

# /usr/local/nagios/libexec/check_mysql -H 192.168.200.111 -unagios -dnagios_monitor -p123qaz!@#

（2）客户端修改 nrpe.cfg

# vim /usr/local/nagios/etc/nrpe.cfg 
command[check_mysql]=/usr/local/nagios/libexec/check_mysql -H 192.168.200.111 -unagios -dnagios_monitor -p123qaz!@#

（3）重启 nrpe

# killall nrpe
# /usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d

（4）服务端定义服务

# vim /usr/local/nagios/etc/servers/192.168.200.111.cfg 
define service{
        use                             generic-service
        host_name                       192.168.200.111
        service_description             check_mysql
        check_command                   check_nrpe!check_mysql
        }

（5）重启 nagios 服务

# service nagios restart

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网站名称：nagios监控mysql（check_mysql）及内存使用率（check_mem）
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