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Configuring an Apache Virtual Server
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Table of Contents
Virtual Web Servers
Single IP Address
Multiple IP Address
Apache
Apache Non-IP Intensive Virtual Server
Apache IP Intensive Virtual Server
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Virtual Web Servers
Single IP Address
Multiple IP Address
The simplest way to configure a World Wide Web Server is to dedicate a single machine as the host for a single web domain. While this configuration is straightforward and easy to establish, it may not make maximum use of the web host's resources. That is, the web domain may not use all of the server's capability or capacity. You can, however, configure a World Wide Web Server as a virtual web host, which means that two or more web domains can share the resources of the server.
From the Internet Service Provider's (ISP's) perspective, a virtual web host provides cost-efficient use of the server and allows the ISP to make more of the server's capacity available for web domain hosting. From the ISP customer's perspective, a virtual web host allows the customer to share the web server with others, while maintaining a unique web domain address. For example, the same web server is available as www.company1.com and www.company2.com.
Consider the example of an ISP who has a server with the domain name www.isp.com. This server provides web space for several customer organizations, including company1 and company2. Without virtual web hosting, these customers are given parts of the web tree on www.isp.com. Their homepages might appear as described in Table 1-1.
Table 1-1: Example Home Pages for a Non-Virtual Host Server
Company URL
company1 http://www.isp.com/company1/
company2 http://www.isp.com/company2/
Each customer organization prefers that their home page appear under their own domain name rather than as a branch of the ISP's server domain name. But, the customer organizations do not want to set up their own internet links and servers. The ISP can define their server as a virtual host, which allows company1 and company2 to each have their own Internet name registrations, www.company1.com and www.company2.org, respectively. These names both correspond to the ISP's server (www.isp.com). The home pages might now appear as shown in Table 1-2.
Table 1-2: Example Home Pages for a Virtual Host Server
Company URL
company1 http://www.company1.com/
company2 http://www.company2.org/
There are two methods you can use to establish your server as a virtual web host. You can configure your web server to use a single instance of the web server and a single IP address, but map the IP address to multiple domain names. Under Apache, the resulting configuration is called a non-IP intensive virtual server.
Alternatively, you can configure your web host to use an instance of the web server and an IP address for each domain name. Under Apache, the resulting configuration is called an IP intensive, or multiple IP, virtual server.
The non-IP intensive method results in multiple domain names that link to the same server instance within the same Web server. The IP intensive method results in multiple virtual server instances linked to the same Web server, with each virtual server instance linked to a particular IP address. When this document discusses a server instance, it refers to a new server configuration under a currently installed Web server.
This document describes the differences between IP and non-IP intensive virtual servers and the pros and cons of each implementation. The document also describes how to configure Apache to implement both types of virtual server.
Most of the information on Apache's implementation of virtual web hosts, including the configuration instructions, comes from the Apache home page. See that page for complete descriptions of all Apache implementations and configuration directives.
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Single IP Address
When you configure your web server as a virtual server using the single IP address method, you establish a single IP address and hostname for that single instance of the web server. For each customer domain name, you map an IP hostname alias to the IP address already associated with the server.
To map an IP hostname alias to the server's IP address, you create canonical name, or CNAME, entries in your DNS (Domain Name System) server for each domain name. For example, if you have a web server defined as www.isp.com, you can configure DNS with multiple CNAME entries that point to www.isp.com. In this way, www.customer1.com, www.customer2.com and other customer domain names can share your ISP server, while each has a unique home page and unique domain name. Apache calls this method of creating a virtual server a non-IP intensive virtual server.
The single IP address method conserves IP addresses, which are a diminishing resource. This method also requires less time and fewer configuration changes, it is easily implemented using CNAME entries, and it allows each customer to share the common server's content settings. Under Apache, you can individualize the settings for the user area (the VirtualHost directive in the configuration file), but the daemon settings for the single IP address are shared by each virtual host.
However, because some browsers do not support the single IP address method, you may have to implement the multiple IP address virtual server method.
To directly access your customer's home page, the user's client browser must support HTTP Version 1.1 protocol (the browser must pass the HTTP_HOST environment variable). If the client browser does not support HTTP Version 1.1, access to the ISP's home page. For browsers that do not support HTTP Version 1.1, the ISP must provide links to the customer home pages.
For information on configuring a virtual server using the single IP address method, see:
Apache Non-IP Intensive Virtual Server
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Multiple IP Address
When you configure your web server as a multiple IP address virtual server, you create an instance of the web server and an IP address you bind to that server instance for each customer domain name. That is, you create a virtual server instance reconfigured from an existing, installed, server for each customer domain name you establish. You do not install a new server. To configure a multiple IP address virtual server, the operating system must also support your ability to define a host name alias for each web server instance and IP address combination (for example, ifconfig alias on Tru64 UNIX).
Apache calls this method of creating a virtual server an IP intensive virtual server.
Unlike the single IP address virtual server method, each virtual server under the multiple IP address method is a separate instance of the web host. Customer sites are not constrained to HTTP Version 1.1 browser support. Under Apache, you can configure an IP intensive virtual server with multiple daemons or a single daemon and control the degree of difference between each virtual server instance.
Under the multiple IP address virtual server method, each server instance is unique and each requires a separate IP address. For an ISP hosting a number of customer domains on the web server, the large number of directories, multiple IP addresses, and the setup configurations for each instance can become a maintenance challenge. On an Apache Web Host server, you can mitigate this situation by configuring virtual servers with the multiple IP address method using a single daemon, rather than multiple daemons. Also note that, on Tru64 UNIX, a single network card can support at least 5000 IP addresses.
For information on configuring a virtual server using the multiple IP address method, see:
Apache IP Intensive Virtual Server
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Apache
Apache Non-IP Intensive Virtual Server
Apache IP Intensive Virtual Server
The method you use to establish the Apache Web Server as a virtual server supporting multiple domain names depends on the version of Apache Web Server you have and the version of HTTP protocol you support.
Version 1.1 and later of the HTTP protocol allows the server to determine the hostname that is referenced by address; thus, you can associate more than one domain name with the IP address that is linked to the server. If you are using an Apache Web Server, Version 1.1 or later and your environment supports HTTP protocol, Version 1.1 or later, you can configure an Apache non-IP address intensive virtual server.
Versions of the HTTP protocol prior to Version 1.1 do not allow a server to determine the hostname that is referenced by address; thus, each server requires a unique IP address. If you are using a version of the Apache Web Server that is earlier than Version 1.1 or your environment does not support a version of HTTP protocol later than Version 1.1, you must configure an Apache IP intensive virtual server.
If the versions of HTTP and Apache in your environment require you to establish a separate IP address and server instance for each virtual server, use the non-IP intensive virtual server method to create an Apache Virtual Web Host. The non-IP intensive virtual server method allows you to conserve the diminishing number of IP addresses while accommodating the growing number of domains.
To define a virtual server, you use VirtualHost directives. When the server gets a request for a document on a particular virtual host, the server uses the VirtualHost directives for that virtual host to properly route and handle the request. Each VirtualHost directive corresponds to a different IP address or to a different host name for the Apache Web Server. If you are configuring a virtual server as an alternate host name, the Web Server must be able to accept IP packets for multiple IP addresses. You can use the Tru64 UNIX ifconfig alias command to configure the Web Server for multiple addresses.
This section summarizes information found on the Apache Web Server home page, http://www.apache.org/, which contains information on configuration of the Apache Server, reference to all directives, release notes, and solutions to various implementation issues.
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Apache Non-IP Intensive Virtual Server
To establish an Apache non-IP intensive virtual server, you must establish a single instance of the server and a single IP address associated with that server. With those prerequisites met, you edit the Apache configuration files to associate two or more domain names with the server and to establish document roots for the home pages of those domains.
Also, you must map an IP address alias to the IP address associated with the server. To map an IP address alias to the server's IP address, you create canonical name, or CNAME, entries in your DNS (Domain Name System) server for each domain name. For example, if you have a web server defined as www.isp.com, you can configure DNS with multiple CNAME entries that point to www.isp.com. In this way, www.customer1.com, www.customer2.com and other customer domain names can share your ISP server, while each has a unique home page and unique domain name.
Ensure that there is an IP address for the Apache Web Host.
Ensure that there is a DNS entry for each new virtual host and that the entry points to the same IP address as the host server. Alternatively, you can include the IP address in the VirtualHost section of the configuration file.
Edit the Apache httpd.conf configuration file to add a VirtualHost section for each domain you wish to link to the host server. The VirtualHost section contains at least a ServerName and DocumentRoot directive and an optional ServerAlias directive.
Reboot the Apache server.
Consider the following example of a VirtualHost section from the httpd.conf configuration file:
<VirtualHost www.apache.org>
ServerName www.apache.org
DocumentRoot /usr/web/apache
ServerAlias apache.org *.apache.org
</VirtualHost>
In this example, you define a virtual host named www.apache.org, whose DNS entry must point to the same IP address as the Apache Web Host server. (You can also use the Apache Web Host server IP address in the VirtualHost directive instead of the Apache Web Host name. The document root for the www.apache.org home page is placed at /usr/web/apache. Also, in this example, you use the ServerAlias directive and a wildcard to ensure that all apache.org addresses (www.apache.org, ftp.apache.org, etc.) point to the Apache Web Host server.
For full documentation on Apache virtual servers, including information on security concerns when using virtual hosts and how to use virtual hosts in an environment containing older browser versions, refer to the documentation repository at the Apache web site.
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Apache IP Intensive Virtual Server
Versions of the HTTP protocol prior to Version 1.1 do not allow a server to determine the host name by which it is addressed, thus, each server requires a unique IP address. If you are using a version of the Apache Web Server that is earlier than Version 1.1 or your environment does not support a Version 1.1, or later, HTTP protocol, you must configure an Apache IP intensive virtual server (multiple IP address method).
Apache has two ways you can configure an IP intensive virtual server:
Run a separate httpd daemon for each hostname.
Use this method when the different virtual hosts need different HTTP configurations, such as different values for ServerType, User, Group, TypesConfig or ServerRoot. Because an increase in the number of running daemons has an impact on operating system performance, you should not use this method if the Apache Web Host server has a high request rate.
Run a single daemon which supports all the virtual hosts.
Use this method when the virtual hosts can share an HTTPD configuration and when the Apache Web Server host services a large number of requests.
Separate daemons for each host name.
To configure an IP intensive virtual server with separate daemons, first create a separate HTTPD installation for each virtual server. For each HTTPD installation, use the BindAddress directive in the httpd.conf configuration file to select the IP address (or virtual host) that the daemon will service.
For example:
BindAddress www.smallco.com
Alternatively, you can specify an IP address instead of the host name, www.smallco.com.
Single daemon for all host names.
To configure an IP intensive virtual server where a single HTTPD daemon services the requests of all virtual hosts, use the VirtualHost directive in the httpd.conf configuration file. In this directive, set different values for ServerAdmin, ServerName, DocumentRoot, ErrorLog and TransferLog for each virtual host the Apache Web Host Server will support. For example:
<VirtualHost www.smallco.com>
ServerAdmin webmaster@mail.smallco.com
DocumentRoot /groups/smallco/www
ServerName www.smallco.com
ErrorLog /groups/smallco/logs/error_log
TransferLog /groups/smallco/logs/access_log
</VirtualHost>
<VirtualHost www.baygroup.org>
ServerAdmin webmaster@mail.baygroup.org
DocumentRoot /groups/baygroup/www
ServerName www.baygroup.org
ErrorLog /groups/baygroup/logs/error_log
TransferLog /groups/baygroup/logs/access_log
</VirtualHost>
Alternatively, you can specify an IP address instead of the host names, www.smallco.com and www.baygroup.com.
| miniyoyo2002 回复于：2002-10-07 11:21:08 |
| 谢谢！ up! |
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