7.7. Configuration

Centrally-managed files are those that are available to multiple systems. Changing a file within a centrally-managed channel may result in changes to several systems.

This page lists all files that are currently stored in your central configuration channels. Click on the Path of a file to be taken to the Configuration File Details page for that file. Select the name of the configuration channel to be taken to the Channel Details page of the channel that contains the file. Clicking on the number of systems takes you to a listing of systems currently subscribed to the channel containing that file. Finally, clicking on the number of overriding systems displays a list of systems that have a local (or override) version of the configuration files (which means that the centrally-managed file will not be deployed to those systems.)

Being able to store and share identical configurations is useful, but what if you have many variations of the same configuration file? What do you do if you have configuration files that differ only in system-specific details, such as hostname and MAC address?

In traditional file management, you would be required to upload and distribute each file separately, even if the distinction is nominal and the number of variations is in the hundreds or thousands. RHN addresses this by allowing the inclusion of macros, or variables, within the configuration files it manages for Provisioning-entitled systems. In addition to variables for custom system information, the following standard macros are supported:

To use this powerful feature, either upload or create a configuration file through the Configuration Channel Details page. Then, open its Configuration File Details page and include the supported macros of your choosing. Ensure that the delimiters used to offset your variables match those set in the Macro Start Delimiter and Macro End Delimiter fields and do not conflict with other characters in the file. We recommend that the delimiters be two characters in length and must not contain the percent (%) symbol.

As an example, you may have a file applicable to all of your servers that differs only in IP address and hostname. Rather than manage a separate configuration file for each server, you may create a single file, such as server.conf, with the IP address and hostname macros included, like so:

hostname={| rhn.system.hostname |}
ip_address={| rhn.system.net_interface.ip_address(eth0) |}

Upon delivery of the file to individual systems, whether through a scheduled action in the RHN website or at the command line with the Red Hat Network Configuration Client (rhncfg-client), the variables will be replaced with the hostname and IP address of the system, as recorded in RHN's System Profile. In the above configuration file, for example, the deployed version resembles the following:

hostname=test.example.domain.com
ip_address=177.18.54.7

To capture custom system information, insert the key label into the custom information macro (rhn.system.custom_info). For instance, if you developed a key labeled "asset" you can add it to the custom information macro in a configuration file to have the value substituted on any system containing it. The macro would look like this:

 
asset={@ rhn.system.custom_info(asset) @}

Upon deployment of the file to a system containing a value for that key, the macro gets translated, resulting in a string similar to the following:

asset=Example#456

To include a default value, for instance if one is required to prevent errors, you can append it to the custom information macro, like so:

asset={@ rhn.system.custom_info(asset) = 'Asset #' @}

This default is overridden by the value on any system containing it.

Using the Red Hat Network Configuration Manager (rhncfg-manager) will not translate or alter files, as that tool is system agnostic — rhncfg-manager does not depend on system settings. Binary files cannot be interpolated.

This page is the default display for the Configuration ⇒ Systems page. The systems displayed here have been fully prepared for configuration file deployment. The number of local and centrally-managed files is displayed. Clicking the name of the system takes you to the System Details ⇒ Configuration ⇒ Overview page for the system. Clicking on the number of local files takes you to the System Details ⇒ Configuration ⇒ View/Modify Files ⇒ Locally-Managed Files page, which allows you to manage which local (override) files apply to the system. Clicking on the number of centrally-managed files takes you to the System Details ⇒ Configuration ⇒ Manage Configuration Channels ⇒ List/Unsubscribe from Channels page. This allows you to unsubscribe from any channels you wish.

This page displays the systems that are either not prepared for configuration file deployment or have not yet been subscribed to a configuration channel. The table has three columns which identify the system name, whether they are prepared for configuration file deployment, and a list of the steps that have yet to be completed before the system is prepared. By selecting the check box to the left of the profile name and then pressing the Enable RHN Configuration Management button, all of the preparatory steps that can be automatically performed are scheduled by RHN.