Configuring Internet Information Services (part 5) - Managing Web Server Configuration Files

Managing Web Server Configuration Files

Although making configuration settings on one or a few servers is easiest using graphical tools, systems administrators often need to configure many Web servers. In addition to using IIS Manager and related tools for configuring settings, you can also configure your Web server by using XML configuration files. In addition, by storing settings in a single file, you can back up and restore settings to other IIS installations easily. In this section, you’ll learn about where Web server and Web site settings are stored.

Understanding ApplicationHost.config

All the configuration settings that have been defined for the local IIS Web server are stored in an XML text file named ApplicationHost.config. The default file system location for these files is %SystemDrive%\Inetpub\History. Within this base folder is a series of folders, each of which contains a copy of the ApplicationHost.config file. The ApplicationHost Helper Service, a default component that is included when you install the Web Server (IIS) role, automatically makes periodic backups of the configuration of the local Web server. This process automatically creates a new folder and a copy of the ApplicationHost.config file. The schema subfolder contains a file that is used to describe and interpret the specific settings that can be used in the configuration files.

An ApplicationHost.config file can be opened and modified, using a standard text editor (such as Windows Notepad) or by using an XML-aware application (such as Visual Studio). The contents are arranged in a hierarchy that defines the various settings and options that can be configured within IIS. (See Figure 19.) Before you make changes directly to a configuration file, be sure to make a backup copy of it. It is fairly easy to introduce changes that can cause errors in IIS.

Figure 19. Using Internet Explorer to view a portion of the ApplicationHost.config file.

Restoring the ApplicationHost.config File

In the event that you need to revert the configuration of IIS to an earlier state by using the automatic backup files, you can copy over the working config file manually. The active version of the ApplicationHost.config file is in the %SystemRoot%\System32\Inetsrv\Config folder. To roll back the configuration of IIS, find the ApplicationHost.config version you want to use and then copy it over the current file. Note that for the changes to be reflected, it might be necessary to restart the Web server and IIS Manager. It is also highly recommended that you copy the current configuration file to a backup location in the event you need to refer to it later.

Understanding Web.config Files

A common problem related to managing Web applications and Web sites is that of retaining settings as sites are moved between servers. In previous versions of IIS, it was often necessary to re-create settings manually to ensure that the site would run properly. IIS 7.0 uses a hierarchical approach to create and manage configuration settings. In addition to the server-level settings that are defined in the ApplicationHost.config file, systems administrators and Web developers can include other settings in Web.config files.

Web.config files can be located within the root folder for a Web site or Web application. These files can contain settings that override the default server-level settings that are included in the ApplicationHost.config file. The format of the files and options is similar. By default, a new Web.config file is created automatically whenever you add a new Web site or a new Web application. The default settings are inherited from the server-level settings unless you specifically change them.

Overall, the hierarchy for configuration files is:

Settings in lower-level files can override settings defined in the parent. A useful benefit of this approach is that the configuration information is included automatically when you choose to copy an entire folder of Web content to another server or to another location on the same server.

Migrating Web Sites and Web Applications

The presence of Web.config files within Web application and Web site folders helps make the process of migrating Web sites to different servers or physical locations simpler. For most applications, all that is required is for all the files within the appropriate folders to be moved or copied to the new location. Then, within IIS Manager, you can re-create any additional Web sites, Web applications, and virtual directories that are required. It is important, however, to test any migrated Web application thoroughly. In some cases, incompatibilities or other issues between server-level and application-level settings can have unintended consequences. Overall, however, the process of moving and copying Web sites is usually fairly simple and straightforward.

Backing Up and Restoring Configuration Data Using AppCmd.exe

An important aspect of Web server administration is ensuring that the configuration of the server is protected against data loss. Because IIS configuration settings are stored automatically in the %SystemDrive%\Inetpub\History folder, ensure that this folder is included in file system backup policies. In addition, it’s important to back up Web sites and Web applications to ensure that they can be restored quickly in the case of a failure. Often, however, you’ll need to create your own configuration backups manually. For example, if you want to transfer configuration data to another IIS installation, or if you want to protect against unwanted changes, it is a good idea to make an on-demand configuration backup.

You can use AppCmd.exe to create a backup of the configuration of IIS and store it to a text file. The utility offers simple capabilities for creating a backup and for restoring from it. The standard command for adding a new backup is:

AppCmd add backup "BackupName"

BackupName specifies the name of the file that you want to create. You can leave off the name, and an automatic filename that includes a timestamp will be generated. The file will be created in the location in which AppCmd.exe was run, but you can always move or copy the file manually to another location.

You can restore the configuration information from the backup, using the following command:

AppCmd restore backup "BackupName"

This process restores the configuration of the IIS Web server to the settings that were included in the backup file. If you want to view a list of backups that have been made, you can use the following command:

AppCmd list backups

You will see a list of all the backup files you have created. Figure 20 shows an example of all these backup-related commands at work.

Figure 20. Performing IIS configuration backup and restore operations by using AppCmd.exe

Using Centralized Configuration for Server Farms

As organizations place a greater reliance on their Web sites and Web-based applications, the ability to improve performance, scalability, and reliability are important goals. With relation to Web servers, a common configuration is known as a Web server farm. In this approach, many Web servers are configured to provide access to the same content. Generally, they have the same configuration settings and either store local copies of Web sites and applications or access them from a shared location.

From a systems administration standpoint, managing large groups of Web servers can be challenging. When configuration changes are required, they often have to be committed manually to many computers. Even with the use of automation or scripting, it is possible to overlook one or a few servers. To support the server farm usage scenario better, IIS 7.0 enables you to share centrally stored configuration data with multiple Web servers.

The first step in the process of creating a shared configuration is to export the configuration of a single IIS server. Generally, you will configure this server with all the settings that you want to use on the other servers. Then, using IIS Manager, click the server name and double-click Shared Configuration in the Features View. To generate an export, click the Export Configuration command in the Actions pane. (See Figure 21.) You will be able to provide a path into which the configuration files will be stored. To protect sensitive information in the configuration files, you must type and confirm an encryption key password. This password will be required to view the settings in the file. You can also use the Connect As option to provide security credentials if you are planning to store the configuration in a network location.

The second step of the process is to place the shared configuration file in a location that is accessible to all the Web servers. Usually, the best choice is a shared network folder on a reliable server. Once you know the path to the files, you can use the Shared Configuration feature to enter the details. First, select the Enable Shared Configuration check box. (See Figure 22.) This will enable you to specify the Physical Path setting. You can use a local file system location or a Universal Naming Convention (UNC)–based network path (for example, \\Server1\WebConfig). The User Name and Password fields enable you to enter the security credentials that will be used by IIS to connect to the physical path you have specified.

Figure 22. Enabling Shared Configuration for an IIS Web server

To save the settings, click the Apply command in the Actions pane. You will be prompted to enter the encryption key password for the configuration files. Once the configuration import is complete, you will be notified that you must restart IIS Manager for it to recognize the configuration changes. You can disable the shared configuration settings later by deselecting the Enable Shared Configuration check box. This returns the Web server to using locally defined configuration settings.