简介
Nagios 是一款自动化运维工具，可以协助运维人员监控服务器的运行状况，并且拥有报警功能。
1、Nagios 核心及插件将安装在/usr/local/nagios 2、Nagios 核心会配置好监控当前服务器的一些基本信息
仅供参考，记录一下centOS7下nagios配置步骤，完整的步骤以及原理请参照原文，原文非常详细！
想要实现的效果是，把一台linux配置为监控主机，这台监控主机监控本机的一些服务，另外还监控一台linux机器和一台windows机器的服务。
nagios的安装：
安装基础支持套件：
[root@nagios-a ~]# yum install gcc glibc glibc-common gd gd-devel xinetd openssl-devel -y
创建系统用户
创建nagios用户并设置密码
/usr/sbin/useradd -m nagios passwd nagios
创建nagcmd用户组，将nagios和apache(web服务器的运行用户)添加至该组
/usr/sbin/groupadd nagcmd
/usr/sbin/usermod -a -G nagcmd nagios
/usr/sbin/usermod -a -G nagcmd apache
下载Nagios安装包
wget -O nagioscore.tar.gz https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.14.tar.gz #下载nagios核心4.4.14
下载的路径在/root下
解压源码包
tar xzf nagioscore.tar.gz #解压源码包
cd nagioscore-nagios-4.4.14/ #解压完成后，切换到nagios目录下
编译配置信息
./configure --with-command-group=nagcmd
编译
make all
安装nagios，并初始化脚本及基础配置文件
make install
make install-init
make install-config
make install-commandmode
配置web服务器
创建apache的配置文件，配置文件目录在/etc/httpd/conf.d/文件下
make install-webconf
为nagios的web界面创建nagiosadmin用户，并设置密码
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin #这个账户是登录nagios网页中的用户，密码设置为123456
把apache加入到开机启动项，并重启apache
systemctl enable httpd.service #把httpd加入到开机启动项中 systemctl restart httpd.service #重启httpd服务
编译并安装nagios插件包
Nagios 实际的监控脚本都是通过插件实现的，本文中的插件包是官方提供插件包（大约50个用于监控的插件）
wget https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz #下载nagios插件plugins-2.2.1
解压插件包
tar -zxvf nagios-plugins-2.2.1.tar.gz
cd nagios-plugins-2.2.1
编译并安装
./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
make all
make install
ls /usr/local/nagios/libexec/|wc -l
#查看插件的个数
启动nagios核心
将nagios核心加入到自动启动列表
chkconfig --add nagios chkconfig nagios on
检查nagios基础配置文件是否有问题
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
重启nagios服务
systemctl restart nagios
开启防火墙端口
firewall-cmd --zone=public --add-port=80/tcp
firewall-cmd --zone=public --add-port=80/tcp --permanent
打开浏览器验证
http://192.168.10.1/nagios 用户名:nagiosadmin 密码:123456
插件装好了，下面修改一下配置文件，设置监控的主机，首先设置监控本机：
在/usr/local/nagios/etc/object/下，有一个localhost.cfg文件，这个文件本来就是存在的，是不需要修改的。
define host {
use linux-server ; Name of host template to use
; This host definition will inherit all variables that are defined
; in (or inherited by) the linux-server host template definition.
host_name localhost
alias 1.121
address 127.0.0.1
}
这样，本机就修改完了，接下来，进行监控windows的配置：
在/usr/local/nagios/etc/object/下，有一个windows.cfg文件，这个文件也是本来就存在的，修改这个文件，使nagios可以监控windows主机，修改这个文件也非常简单，只需要把windows主机的ip地址放在address对应位置就可以了：
define host {
use windows-server ; Inherit default values from a template
host_name winserver ; The name we're giving to this host
alias My Windows Server ; A longer name associated with the host
address 192.168.59.137 ; IP address of the host
}
当然，alias可以改成任意的名字。
重启nagios，可以发现localhost的服务被正常监控，windows主机也可以被ping通，但是windows的服务是监控不到的，这是怎么回事呢，是因为windows没有装nagios插件呀，这样nagios就无法监控到windows的服务了，下面为windows安装nagios插件：
windows下的nagios监控插件名叫NSClient++，访问官网 http://www.nsclient.org，下载安装包，这里我下载的是NSCP-0.5.2.35-x64 .msi，下载完成以后，双击进行安装。
这里我选的是comlete：
安装完成后，记得在服务中把NSClient++服务启动起来：
然后看到有些服务已经起来了，但是有些服务看起来并不能正常监控，下面修改一下windows插件的配置文件，默认安装的位置是在C:\Program Files\NSClient++下，nsclient.ini这个文件就是配置文件了
# If you want to fill this file with all available options run the following command:
# nscp settings --generate --add-defaults --load-all
# If you want to activate a module and bring in all its options use:
# nscp settings --activate-module <MODULE NAME> --add-defaults
# For details run: nscp settings --help
; in flight - TODO
[/settings/default]
; Undocumented key
allowed hosts = 192.200.1.121
; in flight - TODO
[/settings/NRPE/server]
; Undocumented key
verify mode = none
; Undocumented key
insecure = true
; in flight - TODO
[/modules]
; Undocumented key
CheckExternalScripts = enabled
; Undocumented key
CheckHelpers = enabled
; Undocumented key
CheckNSCP = enabled
; Undocumented key
CheckDisk = enabled
; Undocumented key
WEBServer = enabled
; Undocumented key
CheckSystem = enabled
; Undocumented key
NSClientServer = enabled
; Undocumented key
CheckEventLog = enabled
; Undocumented key
NSCAClient = enabled
; Undocumented key
NRPEServer = enabled
把 diable改为enabled，这样服务就能被监控了，改完之后记得去把服务里把NSClient++服务重启一下，然后就能看到监控正常了呢
当然，如果有些服务你不想让他监控，那就去配置文件修改一下监控的内容，比如不想监控一些windows服务，那么就在：windows.cfg文件里把相应的服务注释掉：
#define service {
#
# use generic-service
# host_name winserver
# service_description W3SVC
# check_command check_nt!SERVICESTATE!-d SHOWALL -l W3SVC
#}
# Create a service for monitoring the Explorer.exe process
# Change the host_name to match the name of the host you defined above
#define service {
# use generic-service
# host_name winserver
# service_description Explorer
# check_command check_nt!PROCSTATE!-d SHOWALL -l Explorer.exe
#}
同理，linux的本机localhost.cfg文件，注释掉相应的服务：
#define service {
#
# use local-service ; Name of service template to use
# host_name localhost
# service_description HTTP
# check_command check_http
# notifications_enabled 0
#}
之后重启nagios服务，可以看到注释掉的服务都不见了：
至此，已经配置好了nagios对本机和windows主机的监控，下面进行配置nagios监控其他linux机器：
监控其他linux机器，一般来说需要手动添加两个文件，在安装nagios目录下的 /nagios/etc/object/下，分别是hosts.cfg文件和services.cfg文件，其中hosts.cfg文件主要指定被监控主机的相关情况，包括ip地址以及主机名等；而services.cfg则是定义需要监控的服务等，下面给出简单的配置示例：
hosts.cfg
define host{
use linux-server
host_name 1.131
address 192.168.59.138
}
define host{
use linux-server
host_name 2.76
address 192.168.59.139
}
#####################################################################
define hostgroup{
hostgroup_name test-servers
alias test servers
members 1.131,2.76
}
在hosts.cfg文件中简单定义了两台需要监控的linux主机以及一个主机组，use项是引用了local-service服务的属性值，这个local-service在template.cfg文件中有定义，定义如下：
define host {
name linux-server ; The name of this host template
use generic-host ; This template inherits other values from the generic-host template
check_period 24x7 ; By default, Linux hosts are checked round the clock
check_interval 5 ; Actively check the host every 5 minutes
retry_interval 1 ; Schedule host check retries at 1 minute intervals
max_check_attempts 10 ; Check each Linux host 10 times (max)
check_command check-host-alive ; Default command to check Linux hosts
notification_period workhours ; Linux admins hate to be woken up, so we only notify during the day
; Note that the notification_period variable is being overridden from
; the value that is inherited from the generic-host template!
notification_interval 120 ; Resend notifications every 2 hours
notification_options d,u,r ; Only send notifications for specific host states
contact_groups admins ; Notifications get sent to the admins by default
register 0 ; DON'T REGISTER THIS DEFINITION - ITS NOT A REAL HOST, JUST A TEMPLATE!
}
在services.cfg文件中简单定义了一个服务，用于测试监控主机是否能够正常被监控到：
define service{
use local-service
host_name 1.131,2.76
service_description check-host-alive
check_command check-host-alive
}
现在两个配置文件写好了，然后需要在nagios.cfg（nagios.cfg文件在nagios目录下的etc下）文件中添加对这两个文件的引用，只需要添加以下两行：
cfg_file=/usr/local/nagios/etc/objects/hosts.cfg
cfg_file=/usr/local/nagios/etc/objects/services.cfg
至此，对远端linux主机的简单监控就完成了，重启nagios以后可以看到两台linux主机已经up：
如果想要监控远端主机的多个服务，当然还是要装linux插件的，以远端主机1.131为例，安装nagios插件和nrpe，依然是去nagios官网下载，先增加nagios用户，之后获取nagios插件包和nrpe包，解压后安装：
useradd nagios
wget https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
wget https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-3.2.1/nrpe-3.2.1.tar.gz
tar -zxvf nagios-plugins-2.2.1.tar.gz
tar -zxvf nrpe-3.2.1.tar.gz
cd nagios-plugins-2.2.1/
./configure --prefix=/usr/local/nagios
make
make all
make install
chown nagios.nagios /usr/local/nagios
chown -R nagios.nagios /usr/local/nagios/libexec
cd nrpe-3.2.1/
./configure --prefix=/user/local/nagios
make all
make install
然后，修改一下配置文件，允许监控主机的监控，需要修改的是/usr/local/nagios/etc目录下的nrpe.cfg文件：
allowed_hosts=127.0.0.1,192.168.59.136
这里，只需要在allowed_hosts后加上监控主机的ip就可以了，然后开启nrpe服务，确认端口开启以后去监控主机上测试一下：
/usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d
[root@nagios-b etc]# netstat -tunlp | grep nrpe
tcp 0 0 0.0.0.0:5666 0.0.0.0:* LISTEN 12545/nrpe
tcp6 0 0 :::5666 :::* LISTEN 12545/nrpe
可以看到，端口已经在被监听了，下面去监控主机上测试一下：
[root@nagios-a ~]# /usr/local/nagios/libexec/check_nrpe -H 192.168.59.138
NRPE v3.2.1
正常显示了NRPE的版本
之后可以配置被监控主机的其他服务了，修改监控主机的/usr/local/nagios/etc/objects下的services.cfg，比如修改成这样：
define service{
use local-service
host_name 1.131
service_description check-host-alive
check_command check-host-alive
}
define service {
use local-service
host_name 1.131
service_description PING
check_command check_ping!100.0,20%!500.0,60%
}
# Define a service to check the disk space of the root partition
# on the local machine. Warning if < 20% free, critical if
# < 10% free space on partition.
define service {
use local-service
host_name 1.131
service_description Root Partition
check_command check_local_disk!20%!10%!/
}
# Define a service to check the number of currently logged in
# users on the local machine. Warning if > 20 users, critical
# if > 50 users.
define service {
use local-service
host_name 1.131
service_description Current Users
check_command check_local_users!20!50
}
# Define a service to check the number of currently running procs
# on the local machine. Warning if > 250 processes, critical if
# > 400 processes.
define service {
use local-service
host_name 1.131
service_description Total Processes
check_command check_local_procs!250!400!RSZDT
}
# Define a service to check the load on the local machine.
define service {
use local-service
host_name 1.131
service_description Current Load
check_command check_local_load!5.0,4.0,3.0!10.0,6.0,4.0
}
# Define a service to check the swap usage the local machine.
# Critical if less than 10% of swap is free, warning if less than 20% is free
define service {
use local-service
host_name 1.131
service_description Swap Usage
check_command check_local_swap!20%!10%
}
# Define a service to check SSH on the local machine.
# Disable notifications for this service by default, as not all users may have SSH enabled.
define service {
use local-service
host_name 1.131
service_description SSH
check_command check_ssh
notifications_enabled 0
}
之后检查一下配置文件有没有错误：
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
Nagios Core 4.4.3
Copyright (c) 2009-present Nagios Core Development Team and Community Contributors
Copyright (c) 1999-2009 Ethan Galstad
Last Modified: 2019-01-15
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 20 services.
Checked 4 hosts.
Checked 3 host groups.
Checked 0 service groups.
Checked 1 contacts.
Checked 1 contact groups.
Checked 24 commands.
Checked 5 time periods.
Checked 0 host escalations.
Checked 0 service escalations.
Checking for circular paths...
Checked 4 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
如图输出证明没有问题，之后放心的重启nagios就好了，
可以看到这些服务都可以正常监控了呢！
到这里配置已经完成了，还可以设置一个邮件报警的功能，这个功能的配置是在contacts.cfg这个配置文件中配置的，内容如下：
define contact {
contact_name xiaobai ; Short name of user
use generic-contact ; Inherit default values from generic-contact template (defined above)
alias Nagios Admin ; Full name of user
email *****@***.com ;<<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
}
###############################################################################
#
# CONTACT GROUPS
#
###############################################################################
# We only have one contact in this simple configuration file, so there is
# no need to create more than one contact group.
define contactgroup {
contactgroup_name admins
alias Nagios Administrators
members xiaobai
}
在email出配置上你的地址，就可以收到邮箱报警啦！
至此，对我来说nagios的配置已经全部完成啦！
