Nagios之NRPE监控Linux/UNIX主机

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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。

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。

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：

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

5.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 ~]#grep -v '^#' /usr/local/nagios/etc/nrpe.cfg |sed '/^$/d'log_facility=daemondebug=0pid_file=/usr/local/nagios/var/nrpe.pidserver_port=5666nrpe_user=nagiosnrpe_group=nagiosallowed_hosts=192.183.3.145,172.16.56.131dont_blame_nrpe=0allow_bash_command_substitution=0command_timeout=60connection_timeout=300command[check_users]=/usr/local/nagios/libexec/check_users -w 5 -c 10command[check_load]=/usr/local/nagios/libexec/check_load -w 15,10,5 -c 30,25,20command[check_sda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/sda1command[check_zombie_procs]=/usr/local/nagios/libexec/check_procs -w 5 -c 10 -s Zcommand[check_total_procs]=/usr/local/nagios/libexec/check_procs -w 200 -c 300command[check_swap]=/usr/local/nagios/libexec/check_swap -w 20% -c 10%

6.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

设置自启动：

[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 NagiosCopyright (c) 1999-2008 Ethan Galstad (nagios@nagios.org)Version: 3.0.1Last Modified: 09-08-2016License: GPL v2 with exemptions (-l for more info)SSL/TLS Available: OpenSSL 0.9.6 or higher requiredUsage: 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 commandwith the [command] option you are specifying here.  Upon receipt of the[command] argument, the NRPE daemon will run the appropriate plugin command andsend the plugin output and return code back to *this* plugin.  This allows youto execute plugins on remote hosts and 'fake' the results to make Nagios thinkthe 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 5666NRPE v3.0.1

1.创建命令定义

[root@monitors libexec]# cd /usr/local/nagios/etc/objects/[root@monitors objects]# vim commands.cfgdefine command{        command_name    check_nrpe        command_line    $USER1$/check_nrpe -H "$HOSTADDRESS$"  -c "$ARG1$"}

2.定义host

[root@monitors objects]# vi hosts.cfg

# Define a host for the remote machinedefine host{          host_name kk          alias master-server          use linux-server          address 192.183.3.145          max_check_attempts 5          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         }################################################################################################################################################################ HOST GROUP DEFINITION################################################################################################################################################################ Define an optional hostgroup for Linux machinesdefine hostgroup{        hostgroup_name  remote-linux-servers ; The name of the hostgroup        alias           remoteLinux Servers ; Long name of the group        members         *    ; Comma separated list of hosts that belong to this group        }

3.创建service定义

[root@monitors objects]# vim prilinuxserver.cfg #PRIVATE SERVICE DEFINITIONS#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 fiedefine service{use local-servicehost_name kkservice_description CPU Loadcheck_command check_nrpe!check_loadcontact_groups admins}#The following service will monitor the number of currently logged in users on the remote hostdefine service{use local-servicehost_name kkservice_description Current Userscheck_command check_nrpe!check_userscontact_groups admins}#The following service will monitor the free drive space on /dev/sda1 on the remote host.define service{use local-servicehost_name kkservice_description /dev/sda1 Free Spacecheck_command check_nrpe!check_sda1contact_groups admins}#The following service will monitor the total number of processes on the remote host.define service{use local-servicehost_name kkservice_description Total PProcessescheck_command check_nrpe!check_total_procscontact_groups admins}#The following service will monitor the number of zombie processes on the remote host.define service{use local-servicehost_name kkservice_description Zombie Processescheck_command check_nrpe!check_zombie_procscontact_groups admins}#  monitoring the swap usage on the remote hostdefine service{use local-servicehost_name kkservice_description Swap Usagecheck_command check_nrpe!check_swapcontact_groups admins}

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。

4.启动所定义的命令和服务

[root@monitors objects]# vim /usr/local/nagios/etc/nagios.cfg  添加行：  #definitions for monitoring the remote(linux/unix)hostcfg_file=/usr/local/nagios/etc/objects/hosts.cfg#definitions for monitoring the remote(linux/unix)host private servicescfg_file=/usr/local/nagios/etc/objects/prilinuxserver.cfg

如果host.cfg已经定义过则略过！

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.cfgNagios Core 4.2.0Copyright (c) 2009-present Nagios Core Development Team and Community ContributorsCopyright (c) 1999-2009 Ethan GalstadLast Modified: 08-01-2016License: GPLWebsite: https://www.nagios.orgReading configuration data...   Read main config file okay...Warning: Duplicate definition found for service 'Swap Usage' on host 'kk' (config file '/usr/local/nagios/etc/objects/publinuxserver.cfg', starting on line 75)Warning: Duplicate definition found for service 'Total Processes' on host 'kk' (config file '/usr/local/nagios/etc/objects/publinuxserver.cfg', starting on line 51)Warning: Duplicate definition found for service 'Current Users' on host 'kk' (config file '/usr/local/nagios/etc/objects/publinuxserver.cfg', starting on line 38)   Read object config files okay...Running pre-flight check on configuration data...Checking objects...Checked 20 services.Checked 2 hosts.Checked 2 host groups.Checked 0 service groups.Checked 2 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 hostsChecked 0 service dependenciesChecked 0 host dependenciesChecked 5 timeperiodsChecking global event handlers...Checking obsessive compulsive processor commands...Checking misc settings...Total Warnings: 0Total Errors:   0Things look okay - No serious problems were detected during the pre-flight checkObject precache file created:/usr/local/nagios/var/objects.precache

重启nagios：

[root@monitors objects]#  service nagios restartRunning 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.cfgcommand[check_swap]=/usr/local/nagios/libexec/check_swap -w 20% -c 10%

重启nrpe进程：

[root@kk libexec]#service nrped  restartStopping NRPE daemon... done.Starting NRPE daemon... done.

2.监控端的配置

[root@monitors ~]# vim /usr/local/nagios/etc/objects/prilinuxserver.cfg define service{use generic-servicehost_name remotehostservice_description Swap Usagecheck_command check_nrpe!check_swap}

验证配置：

[root@monitors ~]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

重启nagios：

[root@monitors ~]# service nagios restartRunning configuration check...Stopping nagios: done.Starting nagios: done.

刷新nagios监控页面，可见新配置的监控项！

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！

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