NRPE是Nagios的一个功能扩展，它可在远程Linux/Unix主机上执行插件程序。通过在远程服务器上安装NRPE插件及Nagios插件程序来向Nagios监控平台提供该服务器的本地情况，如CPU负载，内存使用，磁盘使用等。这里将Nagios监控端称为Nagios服务器端，而将远程被监控的主机称为Nagios客户端。
Nagios监控远程主机的方法有多种，其方式包括SNMP，NRPE,SSH,NCSA等。这里介绍其通过NRPE监控远程Linux主机的方式。
NRPE（Nagios Remote Plugin Executor）是用于在远端服务器上运行监测命令的守护进程，它用于让Nagios监控端基于安装的方式触发远端主机上的检测命令，并将检测结果返回给监控端。而其执行的开销远低于基于SSH的检测方式，而且检测过程不需要远程主机上的系统账号信息，其安全性也高于SSH的检测方式。
NRPE有两部分组成
check_nrpe插件：位于监控主机上
nrpe daemon：运行在远程主机上，通常是被监控端agent
注意：nrpe daemon需要Nagios-plugins插件的支持，否则daemon不能做任何监控
当Nagios需要监控某个远程Linux主机的服务或者资源情况时：
首先：Nagios会运行check_nrpe这个插件，告诉它要检查什么；
其次：check_nrpe插件会连接到远程的NRPE daemon，所用的方式是SSL；
然后：NRPE daemon 会运行相应的Nagios插件来执行检查；
最后：NRPE daemon 将检查的结果返回给check_nrpe 插件，插件将其递交给nagios做处理。
一、被监控端安装Nagios-plugins插件和NRPE
1、添加nagios用户
useradd -s /sbin/nologin nagios
2、安装nagios-plugins，因为NRPE依赖此插件
yum -y install gcc gcc-c++ make openssl openssl-devel
tar xf nagios-plugins-2.0.3.tar.gz
cd nagios-plugins-2.0.3
./configure --with-nagios-user=nagios --with-nagios-group=nagios
make all && make install
#注意：如何要监控mysql 需要添加 --with-mysql
3、安装NRPE
tar xf nrpe-2.15.tar.gz cd nrpe-2.15 ./configure --with-nrpe-user=nagios --with-nrpe-group=nagios --with-nagios-user=nagios --with-nagios-group=nagios --enable-command-args --enable-ssl make all make install-plugin make install-daemon make install-daemon-config
4、配置NRPE
vim /usr/local/nagios/etc/nrpc.cfg
log_facility=daemon
pid_file=/var/run/nrpe.pid
server_port=5666 #监听的端口
nrpe_user=nagios
nrpe_group=nagios
allowed_hosts=192.168.110.157 #允许的地址通常是Nagios服务器端
dont_blame_nrpe=0
allow_bash_command_substitution=0
debug=0
command_timeout=60
connection_timeout=300
command[check_users]=/usr/local/nagios/libexec/check_users -w 5 -c 10
command[check_load]=/usr/local/nagios/libexec/check_load -w 15,10,5 -c 30,25,20
command[check_hda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/hda1
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
5、启动NRPE
#以守护进程的方式启动 /usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d netstat -tulpn | grep nrpe tcp 0 0 0.0.0.0:5666 0.0.0.0:* LISTEN 22597/nrpe tcp 0 0 :::5666 :::* LISTEN 22597/nrpe
有两种方式用于管理nrpe服务，nrpe有两种运行模式：
-i # Run as a service under inetd or xinetd -d # Run as a standalone daemon
可以为nrpe编写启动脚本，使得nrpe以standard alone方式运行：
vim /etc/init.d/nrped
#!/bin/bash
# chkconfig: 2345 88 12
# description: NRPE DAEMON
NRPE=/usr/local/nagios/bin/nrpe
NRPECONF=/usr/local/nagios/etc/nrpe.cfg
case "$1" in
start)
echo -n "Starting NRPE daemon..."
$NRPE -c $NRPECONF -d
echo " done."
;;
stop)
echo -n "Stopping NRPE daemon..."
pkill -u nagios nrpe
echo " done."
;;
restart)
$0 stop
sleep 2
$0 start
;;
*)
echo "Usage: $0 start|stop|restart"
;;
esac
exit 0
chmod +x /etc/init.d/nrped
chkconfig --add nrped
chkconfig nrped on
service nrped start
Starting NRPE daemon... done.
netstat -tnlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1031/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1108/master
tcp 0 0 0.0.0.0:5666 0.0.0.0:* LISTEN 22597/nrpe
tcp 0 0 :::22 :::* LISTEN 1031/sshd
tcp 0 0 ::1:25 :::* LISTEN 1108/master
tcp 0 0 :::5666 :::* LISTEN 22597/nrpe
也可以将此命令加入 /etc/rc.local ，以便开机自动启动。 # echo “/usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d” >> /etc/rc.local
二、监控端安装NRPE
1、安装NRPE
# tar xf nrpe-2.15.tar.gz
# cd nrpe-2.15
# ./configure --with-nrpe-user=nagios --with-nrpe-group=nagios --with-nagios-user=nagios --with-nagios-group=nagios --enable-command-args --enable-ssl
# make all
# make install-plugin
#安装完成后，会在Nagios安装目录的libexec下生成check_nrpe的插件
# cd /usr/local/nagios/libexec/
# ll -d check_nrpe
-rwxrwxr-x. 1 nagios nagios 76769 9月 28 08:07 check_nrpe
2、check_nrpe的用法
通过NRPE监控远程Linux主机要使用chech_nrpe插件进行，其语法格式如下：
check_nrpe -H <host> [-n] [-u] [-p <port>] [-t <timeout>] [-c <command>] [-a <arglist...>]
# ./check_nrpe -H 192.168.0.81
NRPE v2.15
3、定义命令
# cd /usr/local/nagios/etc/objects/
# vim commands.cfg
#增加到末尾行
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H "$HOSTADDRESS$" -c "$ARG1$"
}
4、定义服务
cp localhost.cfg linhost.cfg
# vim linhost
define host{
use linux-server
host_name linhost
alias My Linux Server
address 192.168.110.154
}
define service{
use generic-service
host_name linhost
service_description CHECK USER
check_command check_nrpe!check_users
}
define service{
use generic-service
host_name linhost
service_description Load
check_command check_nrpe!check_load
}
define service{
use generic-service
host_name linhost
service_description SDA1
check_command check_nrpe!check_hda1
}
define service{
use generic-service
host_name linhost
service_description Zombie
check_command check_nrpe!check_zombie_procs
}
define service{
use generic-service
host_name linhost
service_description Total procs
check_command check_nrpe!check_total_procs
}
这里重点说下，Nagios服务端定义服务的命令完全是根据被监控端NRPE中内置的监控命令，如下图所示
5、启动所定义的命令和服务
# vim /usr/local/nagios/etc/nagios.cfg #增加一行 cfg_file=/usr/local/nagios/etc/objects/linhost.cfg
6、配置文件语法检查
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
Total Warnings: 0
Total Errors: 0
Things look okay - No serious problems were detected during the pre-flight check
7、重新启动nagios服务
# service nagios restart
8、打开Nagios web监控页面
1）首先点击【Hosts】查看监控主机状态是否为UP
2）其次点击【Services】查看各监控服务的状态是否为OK
