配置WWW服务器是Linux操作平台的重要工作之一，而Apach是目前应用最为广泛的Web服务器产品之一。在Linux下安装Apachc Web服务，Apache服务程序httod启动时需要读取配置文件httpd.conf，以下是一个hupd.conf配置文件的片断：
## httpd.conf--Apache HTTP server configuration file
### Section 1：Global Environment
ServerType standalone
ServerRoot"/etc/httpd"
Timeout 300
KeepAl ive On
MaxKeepAliveRequests 100
KeepAliveTimeout 15
MaxClient 150
###Section 2: ’Main’server configuration
Port 80
User apache
Group apache
ServerAdmin webmaster@abc.com.cn
ServerName www.abc.com.cn
DocumentRoot"/var/www/html"
UserDir public_html
DirectpryIndex index.html
Alias /jianji"/home/zhang/jianji"
ScriptAlias/cgi-bin/"/var/www/cgi-bin/"
ErrorDocument 404/missing.html
###Section 3:Virtual HostS
NameVirtualHost 192.168.10.101
＜VirtualHost 192.168.10.101＞
ServerAdmin webmaster@abc.com.cn
DocumentRoot/www/htdocs/abc
ServerName markert.abc.com.cn
ErrorLog logs/host.some_domain.com-error_log
CustomLog logs/host.some_domain．com_access log common
＜/VirtualHost＞
命令“chkconfig-level 3 httpd on”的功能是什么