Virtual Hosts Configuration

Parallels Plesk Panel for Linux uses the Apache web server for websites hosting. Apache itself does not operate with websites; it manages virtual hosts - web resources identified either by an IP address or a host name. When creating a site, Panel adds a new virtual host to Apache so that the site becomes available through the web server. Panel resides on a virtual host too; this host is called the default virtual host.

When you add a site in Panel, you select one of the hosting types to use with it: web page hosting or forwarding. In terms of Apache, you associate the site with a virtual host of one of three configurations (website hosting, standard forwarding, and frame forwarding). To learn the differences between these configurations, see the section Virtual Hosts and Hosting Types.

Sites are linked to virtual hosts, so if you want to add some feature provided by Apache but not available through the Panel GUI, you should change the virtual host settings using Apache configuration templates. Based on these templates, Panel partly re-generates virtual hosts, so you should follow certain rules when modifying the configuration; otherwise, some of your changes might be lost. Next in this chapter, we will discuss virtual hosts in more detail and provide guidelines on how to modify them safely. To learn more on this point, refer to the section Configuring Virtual Hosts.

Panel creates virtual hosts for websites based on virtual host templates. These templates predefine the content that will be included in each new virtual host. Learn how to change virtual host templates in the section Predefining Virtual Hosts for new Sites.

You can get information on access to each virtual host and Apache errors that have occurred on the host from Apache logs. Learn more about log files location and rotation settings in the section Analyzing Access and Errors.

Virtual Host IP Addresses

The term virtual host refers to the practice of running more than one website on a single server or IP address. For example, Apache can manage two websites, example1.com and example2.com, even if they use a single IP address. Each of these sites is hosted on a separate virtual host.

There are two types of virtual host, each with different methods of requests routing:

• IP-based. Each virtual host has a separate IP address. Apache defines the requested host based on the host IP address.
• Name-based. This supposes that several virtual hosts share the same IP address. To define a requested host, Apache parses the domain name.

Parallels Plesk Panel uses the name-based approach. In addition, Panel provides an option to allocate separate IP addresses to customers who do not want to share their IP address with others. To implement this option, there are two types of IP address in Panel:

• Dedicated IP addresses that have a single owner.
• Shared IP addresses that you can allocate to any number of customers.

Resolving Requests to Web Servers

When a client requests a certain domain, Apache parses the requested domain name. Then Apache searches for the virtual host with the requested domain on the IP address specified in the request. If the host exists, Apache sends the requested files from this host to the client.

If the requested virtual host is not found, Panel uses the following entities to resolve the request:

1. Default domain. This can be created for a specific IP address. If a request to this IP address contains the name of a non-existent domain, Panel redirects this request to the default domain.
2. Default virtual host. This accepts all requests to server IP addresses that could not be directed to any default domain.

Hosting Types

Depending on how you intend to use a domain, for example, to host a site or to forward HTTP requests to another domain, you can choose from three hosting types that define the structure of a virtual host created for this domain. The hosting types are the following:

• Website hosting. When you choose this type of hosting, Panel creates a virtual host (disk space on the local server) for a customer. Customers store their files on a virtual host and run their websites without having to purchase a server and dedicated communication lines.
• Standard forwarding. In this case Panel creates a reduced virtual host that does not store its owner's files and directories.This host is used for redirecting requests to another network resource. When end users try to access the domain, Panel forwards them to another URL. This URL will be shown in their browsers.
• Frame forwarding. In this case Panel creates a reduced virtual host that does not store its owner's files and directories. Unlike standard forwarding, frame forwarding virtual hosts show the requested URL in the browser, not the actual URL. Panel uses the HTML frames to show the pages of another site with the requested URL.

Learn how to change a domain's hosting type in the section Changing Hosting Type.

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