Nagios之NRPE监控Linux/UNIX主机
1. NRPE简介
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。
注意：通过SSH是可以实现在远程的Linux/UNIX主机上执行nagios插件的，比如说check_by_ssh插件就可以实现这项功能。虽然SSH的方式相较于NRPE插件方式更为安全，但是在CPU负载上，无论是监控端还是被监控的远程主机，SSH方式也都更大一些，当面对被监控的主机涉及到成千上百台时，使用这种方式就会是个问题，这也是许多nagios管理员选择使用NRPE方式的主要原因。
1.1 NRPE的设计原理
NRPE插件包括2部分：
![spacer.gif]()
check_nrpe插件，位于本地监控端；NRPE进程，运行于远程主机（Linux/UNIX），也就是被监控端。
当nagios需要监控远程主机（Linux/UNIX）的服务时，NRPE具体的工作流程如下：
Nagios会执行check_nrpe插件，并告诉它需要监控的服务项；
check_nrpe插件通过SSL方式与被监控端的nrpe进程连接；
nrpe进程运行对应的nagios插件来执行服务或资源的监测；
NRPE 进程将监测的结果返回给check_nrpe 插件，check_nrpe插件又将结果传递给nagios进程做后续处理。
注意：NRPE进程能够进行服务与资源监控的前提是：远程主机（Linux/UNIX）必须装有nagios插件。
1.2 NRPE使用案例
1.直接监测
NRPE最直接的使用就是对远程主机的“local”或者“private”资源进行监控，比如CPU负载、内存使用、swap使用、当前的用户数、磁盘的使用情况、进程状态等等。
2.间接监测
当监控端不能够直连远程服务端时，NRPE还可用于间接监控远程主机的“public”服务与资源。比如，已安装nrpe进程和插件的远程主机可以连接远程web服务器（但是监控主机不可以），那么，可以通过配置NRPE进程允许间接监控远程web服务器，在本案例中，NRPE进程相当于监控代理。
2.NRPE安装与配置
本文的测试服务器信息：
监控端IP：172.16.56.131，主机名：monitors
被监控端IP：192.183.3.145，主机名：kk
2.1 远程主机端（被监控端）的NRPE安装与配置
从3.0的版本开始，NRPE在众多的操作系统中的安装都变得更为简单，如有问题可访问https://community.nagios.org/
1.增加nagios用户
[root@kk ~]#useradd nagios
2.下载安装nagios plugins
[root@kk ~]#cd /home/softwares/ [root@kk softwares]#wget http://nagios-plugins.org/download/nagios-plugins-2.1.2.tar.gz [root@kk softwares]#tar -xzf nagios-plugins-2.1.2.tar.gz [root@kk softwares]#cd nagios-plugins-2.1.2 [root@kk nagios-plugins-2.1.2]#./configure --with-nagios-user=nagios --with-nagios-group=nagios
注意：要监控MySQL需要添加 --with-mysql。
[root@kk nagios-plugins-2.1.2]#make [root@kk nagios-plugins-2.1.2]#make install
修改nagios插件安装目录权限：
[root@kk nagios-plugins-2.1.2]# chown nagios.nagios /usr/local/nagios [root@kk nagios-plugins-2.1.2]# chown -R nagios.nagios /usr/local/nagios/libexec
3.安装NRPE
NRPE下载地址https://sourceforge.net/projects/nagios/files/nrpe-3.x/，本文下载版本是nrpe-3.0.1.tar.gz。
[root@kk nagios-plugins-2.1.2]#cd .. [root@kk softwares]#tar zxf nrpe-3.0.1.tar.gz [root@kk softwares]#cd nrpe-3.0.1 [root@kk nrpe-3.0.1]#yum -y install openssl openssl-devel [root@kk nrpe-3.0.1]#./configure --with-nagios-user=nagios --with-nagios-group=nagios
[root@kk nrpe-3.0.1]#make all
4.安装NRPE的plugin、deamon等
[root@kk nrpe-3.0.1]#make install-plugin
[root@kk nrpe-3.0.1]#make install-daemon
[root@kk nrpe-3.0.1]#make install-daemon-config
这是nrpe该版本的一个bug，详见https://github.com/NagiosEnterprises/nrpe/issues/50。
解决：
[root@kk nrpe-3.0.1]#make install-config
如果需要打开5666端口，则需要下列命令（本案例默认关闭的防火墙）：
# iptables -I RH-Firewall-1-INPUT -p tcp -m tcp –dport 5666 -j ACCEPT # service iptables save
4.配置NRPE命令
[root@kk nrpe-3.0.1]#vim /usr/local/nagios/etc/nrpe.cfg
修改allowed_hosts=192.183.3.145,172.16.56.131，允许Nagios服务器端访问；
在命令行测试如下的监测命令，这里根据自己的监测需求对命令进行修改，并写入nrpe.cfg文件：
/usr/local/nagios/libexec/check_nrpe -H localhost -c check_users /usr/local/nagios/libexec/check_nrpe -H localhost -c check_load /usr/local/nagios/libexec/check_nrpe -H localhost -c check_sda1 /usr/local/nagios/libexec/check_nrpe -H localhost -c check_total_procs /usr/local/nagios/libexec/check_nrpe -H localhost -c check_zombie_procs
查看配置结果：
[root@kk libexec]#grep -v '^#' /usr/local/nagios/etc/nrpe.cfg |sed '/^$/d' log_facility=daemon debug=0 pid_file=/usr/local/nagios/var/nrpe.pid server_port=5666 nrpe_user=nagios nrpe_group=nagios allowed_hosts=192.183.3.145,172.16.56.131 dont_blame_nrpe=0 allow_bash_command_substitution=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_sda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/sda1 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
[root@kk nrpe-3.0.1]# /usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d [root@kk nrpe-3.0.1]#netstat -tulpn | grep 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@kk nrpe-3.0.1]#vi /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@kk nrpe-3.0.1]#chmod +x /etc/init.d/nrped [root@kk nrpe-3.0.1]#chkconfig --add nrped [root@kk nrpe-3.0.1]#chkconfig nrped on [root@kk nrpe-3.0.1]#service nrped start Starting NRPE daemon... done.
2.2 监控端NRPE安装与配置
1.安装依赖包
[root@monitors ~]# yum -y install openssl openssl-devel
否则编译nrpe时会出现如下问题：
原因是缺少openssl-devel包。
2. NRPE下载与安装
[root@monitors ~]# cd /home/nagios/ [root@monitors nagios]# wget http://prdownloads.sourceforge.net/sourceforge/nagios/nrpe-3.0.1.tar.gz--2017-01-17 23:36:36-- http://prdownloads.sourceforge.net/sourceforge/nagios/nrpe-3.0.1.tar.gz [root@monitors nagios]# tar xzvf nrpe-3.0.1.tar.gz [root@monitors nagios]# cd nrpe-3.0.1 [root@monitors nrpe-3.0.1]# ./configure --with-nagios-user=nagios --with-nagios-group=nagios
[root@monitors nrpe-3.0.1]# make all
[root@monitors nrpe-3.0.1]# 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，如下所示：
[root@monitors nrpe-3.0.1]# ll /usr/local/nagios/libexec/check_nrpe -rwxrwxr-x 1 nagios nagios 125293 1月 17 23:47 /usr/local/nagios/libexec/check_nrpe
3.NRPE测试
NRPE命令参数的使用可参详：
[root@monitors libexec]# ./check_nrpe -h NRPE Plugin for Nagios Copyright (c) 1999-2008 Ethan Galstad (nagios@nagios.org) Version: 3.0.1 Last Modified: 09-08-2016 License: GPL v2 with exemptions (-l for more info) SSL/TLS Available: OpenSSL 0.9.6 or higher required Usage: check_nrpe -H <host> [-2] [-4] [-6] [-n] [-u] [-V] [-l] [-d <dhopt>] [-P <size>] [-S <ssl version>] [-L <cipherlist>] [-C <clientcert>] [-K <key>] [-A <ca-certificate>] [-s <logopts>] [-b <bindaddr>] [-f <cfg-file>] [-p <port>] [-t <interval>:<state>] [-c <command>] [-a <arglist...>] Options: <host> = The address of the host running the NRPE daemon -2 = Only use Version 2 packets, not Version 3 -4 = bind to ipv4 only -6 = bind to ipv6 only -n = Do no use SSL -u = (DEPRECATED) Make timeouts return UNKNOWN instead of CRITICAL -V = Show version -l = Show license <dhopt> = Anonymous Diffie Hellman use: 0 = Don't use Anonymous Diffie Hellman (This will be the default in a future release.) 1 = Allow Anonymous Diffie Hellman (default) 2 = Force Anonymous Diffie Hellman <size> = Specify non-default payload size for NSClient++ <ssl ver> = The SSL/TLS version to use. Can be any one of: SSLv2 (only), SSLv2+ (or above), SSLv3 (only), SSLv3+ (or above), TLSv1 (only), TLSv1+ (or above DEFAULT), TLSv1.1 (only), TLSv1.1+ (or above), TLSv1.2 (only), TLSv1.2+ (or above) <cipherlist> = The list of SSL ciphers to use (currently defaults to "ALL:!MD5:@STRENGTH". WILL change in a future release.) <clientcert> = The client certificate to use for PKI <key> = The private key to use with the client certificate <ca-cert> = The CA certificate to use for PKI <logopts> = SSL Logging Options <bindaddr> = bind to local address <cfg-file> = configuration file to use [port] = The port on which the daemon is running (default=5666) [command] = The name of the command that the remote daemon should run [arglist] = Optional arguments that should be passed to the command, separated by a space. If provided, this must be the last option supplied on the command line. NEW TIMEOUT SYNTAX -t <interval>:<state> <interval> = Number of seconds before connection times out (default=10) <state> = Check state to exit with in the event of a timeout (default=CRITICAL) Timeout state must be a valid state name (case-insensitive) or integer: (OK, WARNING, CRITICAL, UNKNOWN) or integer (0-3) 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 <host> [-n] [-u] [-p <port>] [-t <timeout>] [-c <command>] [-a <arglist...>]
[root@monitors libexec]# ./check_nrpe -H 192.183.3.145 -p 5666 NRPE v3.0.1
1.创建命令定义
[root@monitors libexec]# cd /usr/local/nagios/etc/objects/
[root@monitors objects]# vim commands.cfg
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H "$HOSTADDRESS$" -c "$ARG1$"
}
2.创建host与service定义
[root@monitors objects]# vim linuxserver.cfg
#############################################################
#create a new template for linux boxes
#############################################
define host{
name linux-box ; Name of this template
use generic-host ; Inherit default values
check_period 24x7
check_interval 5
retry_interval 1
max_check_attempts 10
check_command check-host-alive
notification_period 24x7
notification_interval 30
notification_options d,r
contact_groups admins
register 0 ; DONT REGISTER THIS - ITS A TEMPLATE
}
########################################################
#defie a new host for the remote Linux/Unix box
#that references the newly created linux-box host template
########################################################
define host{
use linux-box ; Inherit default values from a template
host_name remotehost ; The name we're giving to this
server
alias centos6_kk ; A longer name for the server
address 192.183.3.145 ; IP address of the server
}
######################################################################################
#The following service will monitor the CPU load on the remote host.
# The "check_load" argument that is passed to the check_nrpe command
# defiition tells the NRPE daemon to run the "check_load" comman#d as defied in the nrpe.cfg fie
######################################################################################
define service{
use generic-service
host_name remotehost
service_description CPU Load
check_command check_nrpe!check_load
}
##############################################################################################
#The following service will monitor the number of currently logged in users on the remote host
############################################################################################
define service{
use generic-service
host_name remotehost
service_description Current Users
check_command check_nrpe!check_users
}
#############################################################################################
#The following service will monitor the free drive space on /dev/sda1 on the remote host.
view plain copy print?
#<span style="color:#ff0000;">
#注意：这里的/dev/sda1是通过被检测主机df命令获得，切勿根据官方文档盲目填写/dev/hda1
############################################################################################
define service{
use generic-service
host_name remotehost
service_description /dev/sda1 Free Space
check_command check_nrpe!check_sda1
}
##############################################################################################
#The following service will monitor the total number of processes on the remote host.
##############################################################################################
define service{
use generic-service
host_name remotehost
service_description Total Processes
check_command check_nrpe!check_total_procs
}
###########################################################################################
#The following service will monitor the number of zombie processes on the remote host.
###########################################################################################
define service{
use generic-service
host_name remotehost
service_description Zombie Processes
check_command check_nrpe!check_zombie_procs
}
注意：监控端（Nagios服务端）定义的service命令与被监控端NRPE中内置的监控命令一致。
3.启动所定义的命令和服务
[root@monitors objects]# vim /usr/local/nagios/etc/nagios.cfg 添加一行： cfg_file=/usr/local/nagios/etc/objects/linuxserver.cfg
配置语法检查：
[root@monitors objects]# service nagios configtest 或者 [root@monitors objects]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg Nagios Core 4.2.0 Copyright (c) 2009-present Nagios Core Development Team and Community Contributors Copyright (c) 1999-2009 Ethan Galstad Last Modified: 08-01-2016 License: GPL Website: https://www.nagios.org Reading configuration data... Read main config file okay... Read object config files okay... Running pre-flight check on configuration data... Checking objects... Checked 15 services. Warning: Host 'kk' has no default contacts or contactgroups defined! Checked 2 hosts. Checked 1 host groups. Checked 1 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 2 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: 1 Total Errors: 0 Things look okay - No serious problems were detected during the pre-flight check
重启nagios：
[root@monitors objects]# service nagios restart Running configuration check... Stopping nagios: done. Starting nagios: done.
登录Nagios web监控页面查看配置的监控是否生效：
至此，NRPE的简单安装与配置结束！
4. NRPE自定义配置
如果需要监控远程主机（Linux/UNIX）更多的服务，需要：
在远程主机端的nrpe.cfg文件中增加新的命令定义；
在监控端的nagios配置文件中增加新的服务监控定义；
比如说增加swap空间的使用率监控。
1．被监控远程主机端配置
在本例中假定想要的结果是当swap空闲率低于10%将会有“critical”警告，低于20%将有“warning”警告；
[root@kk libexec]#/usr/local/nagios/libexec/check_swap -w 20% -c 10% SWAP OK - 59% free (2251 MB out of 3823 MB) |swap=2251MB;764;382;0;3823
将该命令添加至nrpe.cfg文件中：
[root@kk libexec]#vi /usr/local/nagios/etc/nrpe.cfg command[check_swap]=/usr/local/nagios/libexec/check_swap -w 20% -c 10%
重启nrpe进程：
[root@kk libexec]#service nrped restart Stopping NRPE daemon... done. Starting NRPE daemon... done.
2.监控端的配置
[root@monitors ~]# vim /usr/local/nagios/etc/objects/linuxserver.cfg
define service{
use generic-service
host_name remotehost
service_description Swap Usage
check_command check_nrpe!check_swap
}
验证配置：
[root@monitors ~]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg Nagios Core 4.2.0 Copyright (c) 2009-present Nagios Core Development Team and Community Contributors Copyright (c) 1999-2009 Ethan Galstad Last Modified: 08-01-2016 License: GPL Website: https://www.nagios.org Reading configuration data... Read main config file okay... Read object config files okay... Running pre-flight check on configuration data... Checking objects... Checked 16 services. Warning: Host 'kk' has no default contacts or contactgroups defined! Checked 2 hosts. Checked 1 host groups. Checked 1 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 2 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: 1 Total Errors: 0 Things look okay - No serious problems were detected during the pre-flight check
重启nagios：
[root@monitors ~]# service nagios restart Running configuration check... Stopping nagios: done. Starting nagios: done.
刷新nagios监控页面：
成功！
附注：本文理论部分参阅NRPE 3.0官方文档，实践部分有参阅http://467754239.blog.51cto.com/4878013/1558897/，欢迎批评指正！
