Issue #4 February 2005

Red Hat Speaks

Robin Norwood, Red Hat Network web engineer

Red Hat Network is a complete systems management platform for Linux. It lets administrators apply system updates, monitor desktop and servers, duplicate system configurations, and more. For an overview, take the Red Hat Network virtual tour. Want to learn more? This month Red Hat Magazine interviewed Robin Norwood from the RHN team to provide a closer look into the features of Red Hat Network.

How long have you worked at Red Hat and what is your role on the Red Hat Network team?
I started working for Red Hat three years ago. I came to Red Hat from a (very) small web design company in Tennessee. I'm on the RHN web development team.
How do RHN user and system groups work?
A Management entitled system can be in any number of system groups. In addition to the web interface that allows an administrator to perform an action on all of the systems in a group, the system group is our way of granting permission to manage systems to normal users. A normal user can also be assigned as 'administrator' of a group. This gives the user complete control over all of the systems in the group. If a system is not in a group that the user is an administrator of, then the user has no access to the system.
The example I usually give of this is an organization that has an east coast group, a west coast group, a web server group, and a database server group. The user who administers the east coast servers has administration rights to the 'east coast' group and therefore all the systems on the east coast, regardless of whether they are web servers or database servers. Your database administrators have rights to the 'database servers' group and therefore all of the DB servers, east coast and west coast. Of course, the organization administrator has access to all of the systems registered to the organization, regardless of what groups they are in.
What is an entitlement?
In RHN, an entitlement is associated with a set of features or a set of channels. System entitlements, or modules, include Updates, Management, and Provisioning. The Updates entitlement provides basic functionality for package and errata updates and is ideal for keeping a few systems up to date. The Management entitlement adds functionality including system grouping and searching capabilities and is extremely useful when managing large groups of systems. The provisioning entitlement is available as an add-on for Management systems and allows configuration management and kickstart support. Refer to for the latest information on entitlements.
After I schedule an update for my web server, how does the update get installed from the RHN servers to my web server?
All Red Hat Enterprise Linux systems have a service running by default called rhnsd. This service is configured to run the rhn_check utility every two hours. rhn_check communicates via XMLRPC to the main RHN servers or your organization's RHN Proxy or RHN Satellite server. If there are any pending actions scheduled such as a package update the system will perform that action at that time. A new feature we have available with our 3.6 Satellite product uses a push technology to cause the scheduled actions to be recognized and performed by the target systems almost immediately.
Can updates be scheduled during my company's scheduled maintenance times?
Yes. Most actions can be scheduled for a specific time of day within the limits of the two-hour check in window. If you require more control, you should look at the RHN Satellite product and the push technology I mentioned before.
Does RHN keep a history of actions that are performed on each of my registered systems?
Yes. Each system has a history associated with it found under the Events tab for that system. This history shows all of the scheduled action that the system has completed or attempted to complete. You can also view the pending actions for a system from this interface.
As part of the Provisioning module, how does RHN know which parts of my operating system to backup so it can be cloned?
It doesn't. Since system configurations can vary widely, we provide two tools to manage your configuration. The first is our Configuration Management feature. Configuration Management allows you to specify a set of files associated with a system which are managed via RHN either using the web interface or the rhncfg utilities. You can upload configuration files to RHN where they are stores centrally. You can modify the files uploaded and then re-deploy them to the original system or any other system in your organization. Configuration files can be organized in channels so that similar sets of systems get the same configuration. Files which need to vary from system to system can be overridden on a per-system basis.
The second tool we provide is the 'file preservation list,' which is a list of files that can be associated with a Kickstart Profile. When a kickstart is scheduled via RHN, these files are automatically preserved and redeployed on the system after the kickstart is complete. While only a limited amount of space is available (approximately 1MB), this tool can be very useful to preserve system configuration across kickstarts.
Using the RHN Management module, can companies create custom channels that provide alternate version of packages already provided in Enterprise Linux?
Yes, though the custom channels feature is only available to users of the RHN Proxy or RHN Satellite products. Generally, a custom child channel is used to store packages that an organization provides in addition to those found in the base Enterprise Linux channel. However, if an organization wants to have more control, they can create a clone of a Enterprise Linux channel on their RHN Satellite and override specific package versions in that cloned channel.
Can the RHN Provisioning module be used to upgrade from one version of Red Hat Enterprise Linux to a new version such as v.3 to v.4?
Yes. The standard method for installing an Enterprise Linux system in a non-interactive way is to use the kickstart feature. This allows an administrator to specify all of the install-time options for a system in a configuration file. The administrator also provides a repository of the files required for the install, usually available via HTTP or FTP. RHN manages the kickstart configuration files, schedules the required actions, and, with an RHN Satellite server, provides a file repository for each version of Enterprise Linux. An administrator can then schedule a system kickstart from the web interface which the target system will pick up and begin an unattended install.
What would you say is the quality that makes you so irresistible to women?
I would have to say that it is the air of mystery I convey. Nothing excites the imagination of a woman more than a mystery. Except perhaps flightless tuxedo-wearing waterfowl.