Nagios利用NRPE监控Linux主机

一、简介

1、NRPE介绍

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。

2、NRPE的工作原理

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

详细的介绍NRPE的工作原理

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。
 

二、被监控端安装Nagios-plugins插件和NRPE

1、添加nagios用户

[root@ClientNrpe ~]# useradd -s /sbin/nologin nagios

2、安装nagios-plugins，因为NRPE依赖此插件

[root@ClientNrpe ~]# yum -y install gcc gcc-c++ make openssl openssl-devel

[root@ClientNrpe ~]# tar xf nagios-plugins-2.0.3.tar.gz
[root@ClientNrpe ~]# cd nagios-plugins-2.0.3
[root@ClientNrpe nagios-plugins-2.0.3]# ./configure  --with-nagios-user=nagios --with-nagios-group=nagios
[root@ClientNrpe nagios-plugins-2.0.3]# make && make install

#注意：如何要监控mysql 需要添加 --with-mysql

3、安装NRPE

[root@ClientNrpe ~]# tar xf nrpe-2.15.tar.gz
[root@ClientNrpe ~]# cd nrpe-2.15
[root@ClientNrpe 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
[root@ClientNrpe nrpe-2.15]# make all
[root@ClientNrpe nrpe-2.15]# make install-plugin
[root@ClientNrpe nrpe-2.15]# make install-daemon
[root@ClientNrpe nrpe-2.15]# make install-daemon-config

4、配置NRPE

[root@ClientNrpe ~]# grep -v '^#' /usr/local/nagios/etc/nrpe.cfg |sed '/^$/d'
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=192.168.0.105   #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
[root@ClientNrpe ~]# /usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d
[root@ClientNrpe ~]# 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：

[root@ClientNrpe ~]# cat /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
[root@ClientNrpe ~]# chmod +x /etc/init.d/nrped
[root@ClientNrpe ~]# chkconfig --add nrped
[root@ClientNrpe ~]# chkconfig nrped on

[root@ClientNrpe ~]# service nrped start
Starting NRPE daemon... done.
[root@ClientNrpe ~]# 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

三、监控端安装NRPE

1、安装NRPE

[root@Nagios ~]# tar xf nrpe-2.15.tar.gz
[root@Nagios ~]# cd nrpe-2.15
[root@Nagios 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
[root@Nagios nrpe-2.15]# make all
[root@Nagios nrpe-2.15]# 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
[root@Nagios ~]# cd /usr/local/nagios/libexec/
[root@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
 

[root@Nagios libexec]# ./check_nrpe -h

NRPE Plugin for Nagios
Copyright (c) 1999-2008 Ethan Galstad ([e-mail])
Version: 2.15
Last Modified: 09-06-2013
License: GPL v2 with exemptions (-l for more info)
SSL/TLS Available: Anonymous DH Mode, OpenSSL 0.9.6 or higher required

Usage: check_nrpe -H  [ -b  ] [-4] [-6] [-n] [-u] [-p ] [-t ] [-c ] [-a ]

Options:
 -n         = Do no use SSL
 -u         = Make socket timeouts return an UNKNOWN state instead of CRITICAL
      = The address of the host running the NRPE daemon
  = bind to local address
 -4         = user ipv4 only
 -6         = user ipv6 only
 [port]     = The port on which the daemon is running (default=5666)
 [timeout]  = Number of seconds before connection times out (default=10)
 [command]  = The name of the command that the remote daemon should run
 [arglist]  = Optional arguments that should be passed to the command.  Multiple
              arguments should be separated by a space.  If provided, this must be
              the last option supplied on the command line.

Note:
This plugin requires that you have the NRPE daemon running on the remote host.
You must also have configured the daemon to associate a specific plugin command
with the [command] option you are specifying here.  Upon receipt of the
[command] argument, the NRPE daemon will run the appropriate plugin command and
send the plugin output and return code back to *this* plugin.  This allows you
to execute plugins on remote hosts and 'fake' the results to make Nagios think
the plugin is being run locally.

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  [-n] [-u] [-p ] [-t ] [-c ] [-a ]

[root@Nagios libexec]# ./check_nrpe -H 192.168.0.81
NRPE v2.15

3、定义命令

[root@Nagios ~]# cd /usr/local/nagios/etc/objects/
[root@Nagios 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

	
[root@Nagios objects]# cp windows.cfg linhost.cfg
[root@Nagios objects]# grep -v '^#' linhost.cfg |sed '/^$/d'
define host{
    use     linux-server
    host_name   linhost
    alias       My Linux Server
    address     192.168.0.81
    }
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

	
[root@Nagios ~]# 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

	
[root@Nagios ~]# service nagios configtest

Nagios Core 4.0.7
Copyright (c) 2009-present Nagios Core Development Team and Community Contributors
Copyright (c) 1999-2009 Ethan Galstad
Last Modified: 06-03-2014
License: GPL

Website:
Reading configuration data...
   Read main config file okay...
   Read object config files okay...

Running pre-flight check on configuration data...

Checking objects...
    Checked 20 services.
    Checked 3 hosts.
    Checked 2 host groups.
    Checked 0 service groups.
    Checked 1 contacts.
    Checked 1 contact groups.
    Checked 26 commands.
    Checked 5 time periods.
    Checked 0 host escalations.
    Checked 0 service escalations.
Checking for circular paths...
    Checked 3 hosts
    Checked 0 service dependencies
    Checked 0 host dependencies
    Checked 5 timeperiods
Checking global event handlers...
Checking obsessive compulsive processor commands...
Checking misc settings...

Total Warnings: 0
Total Errors:   0

Things look okay - No serious problems were detected during the pre-flight check
Object precache file created:
/usr/local/nagios/var/objects.precache

7、重新启动nagios服务

	
[root@Nagios ~]# service nagios restart
Running configuration check...
Stopping nagios: done.
Starting nagios: done.

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

注意：在监控新添加的主机linhost；出现状态为CRITICAL，提示没有那个文件或目录。下面是解决办法

在监控Linhost主机时出现一个CRITICAL的警告，查找解决办法

	
###被监控端修改NRPE配置文件并重启NRPE服务
[root@ClientNrpe etc]# vim nrpe.cfg
command[check_sda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/sda1
[root@ClientNrpe etc]# service nrped restart

###监控端修改linhost.cfg配置文件并重启nagios和httpd服务
[root@Nagios objects]# vim linhost.cfg
#注释：原来这里是hda1，现在修改成sda1
define service{
        use                     generic-service
        host_name               linhost
        service_description     SDA1
        check_command           check_nrpe!check_sda1
        }
[root@Nagios ~]# service nagios restart
Running configuration check...
Stopping nagios: done.
Starting nagios: done.
[root@Nagios ~]# service httpd restart
停止 httpd：                                               [确定]
正在启动 httpd：                                           [确定]

再次点击【services】即为刷新页面，查看如下图所示：