首先我参看的是Nagios的官方文档，Nagios – Installing Nagios Core From Source——The Industry Standard in IT Infrastructure Monitoring，但是文档写的不够详细，对于安装的部分写的过于简略，缺少了几个步骤。
下面我将叙述详细步骤。
#首先安装必要的软件包：
sudo apt-get install wget build-essential apache2 php5-gd libgd2-xpm libgd2-xpm-dev libapache2-mod-php5
#下载软件包
cd /tmp
wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.4.1.tar.gz
wget http://sourceforge.net/projects/nagiosplug/files/nagiosplug/1.4.15/nagios-plugins-1.4.15.tar.gz
#添加组和用户
useradd nagios
groupadd nagcmd
usermod -a -G nagcmd nagios
#解压缩
tar zxvf nagios-3.4.1.tar.gz
tar zxvf nagios-plugins-1.4.15.tar.gz
cd nagios
./configure --with-nagios-group=nagios --with-command-group=nagcmd -–with-mail=/usr/bin/sendmail
cd /tmp/nagios-plugins-1.4.15
./configure --with-nagios-user=nagios --with-nagios-group=nagios
#安装
make all
# 使用make install来安装主程序,CGI和HTML文件
make install
# 使用make install-init在/etc/rc.d/init.d安装启动脚本
make install-init
# 使用make install-cofig来安装示例配置文件,安装的路径是/usr/local/nagios/etc.
make install-config
# 使用make install-commandmode来配置目录权限
make install-commandmode
Nagios目录功能的简要说明：
- bin Nagios执行程序所在目录，nagios文件即为主程序
- etc Nagios配置文件位置
- sbin Nagios Cgi文件所在目录，也就是执行外部命令所需文件所在的目录
- Share Nagios网页文件所在的目录
- var Nagios日志文件、spid 等文件所在的目录
- var/archives 日志归档目录
- var/rw 用来存放外部命令文件
#配置apache
将下面的行加入apache配置文件/etc/apache2/httpd.conf的alias模块<IfModule alias_module>，因为我的httpd.conf文件为空，因此自行创建了该模块。
<IfModule alias_module>
#
# Redirect: Allows you to tell clients about documents that used to
# exist in your server's namespace, but do not anymore. The client
# will make a new request for the document at its new location.
# Example:
# Redirect permanent /foo http://localhost/bar #
# Alias: Maps web paths into filesystem paths and is used to
# access content that does not live under the DocumentRoot.
# Example:
# Alias /webpath /full/filesystem/path
#
# If you include a trailing / on /webpath then the server will
# require it to be present in the URL. You will also likely
# need to provide a <Directory> section to allow access to
# the filesystem path. #
# ScriptAlias: This controls which directories contain server scripts.
# ScriptAliases are essentially the same as Aliases, except that
# documents in the target directory are treated as applications and
# run by the server when requested rather than as documents sent to the
# client. The same rules about trailing "/" apply to ScriptAlias
# directives as to Alias.
#
ScriptAlias /nagios/cgi-bin "/usr/local/nagios/sbin"
<Directory "/usr/local/nagios/sbin">
# SSLRequireSSL
Options ExecCGI
AllowOverride None
Order allow,deny
Allow from all
# Order deny,allow
# Deny from all
# Allow from 127.0.0.1
AuthName "Nagios Access"
AuthType Basic
AuthUserFile /usr/local/nagios/etc/htpasswd.users
Require valid-user
</Directory>
Alias /nagios "/usr/local/nagios/share"
<Directory "/usr/local/nagios/share">
# SSLRequireSSL
Options None
AllowOverride None
Order allow,deny
Allow from all
# Order deny,allow
# Deny from all
# Allow from 127.0.0.1
AuthName "Nagios Access"
AuthType Basic
AuthUserFile /usr/local/nagios/etc/htpasswd.users
Require valid-user
</Directory>
</IfModule>
# 创建apache目录验证文件
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
New password: (输入密码)
Re-type new password: (再输入一次密码)
Adding password for user nagiosadmin
# 重启apache：
service apache2 restart
# 检查Nagios配置文件
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
# 启动Nagios
service nagios start
在浏览器中打开http://<your.nagios.server.ip>/nagios。
Nagios主界面如下图：
登录时要求输入用户名密码，用户名是nagiosadmin，密码即为上面你自己设置的密码。
安装完成。
参考：
http://bbs.chinaunix.net/thread-1394907-1-1.html 【Nagios3.0.5在CentOS5.2中安装（一） 】
http://blog.163.com/jackswu@yeah/blog/static/140629123201091675325673/ 【Apache项目路径重定位】
http://www.ibm.com/developerworks/cn/linux/l-ganglia-nagios-2/ 【Ganglia 和 Nagios，第 2 部分: 使用 Nagios 监视企业集群】