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I’ve had a couple of questions on this in the last week, and wanted to post the how-to here:
Q: How can I demonstrate or test cross-platform monitoring in SCOM 2007 R2 without purchasing a RHEL (RedHat), Suse or other license?
A: In truth, both of these distributions have a trial download (60 days in each case I think), but there is also a way you can setup a long-term demo with no license purchase at all using CentOS. We’ll simply change the OS caption…Read on for details on the process and why CentOS looks so much like RHEL.
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This scenario is very real to me, as we do have a couple of VM hosts running CentOS 5 and VMware Server in my organization. So while it may not be supported, by one method or another,monitoring our CentOS systems is something we have to do
While unsealing and modifying a copy of the RHEL 5 MP is possible as has been alluded to in the blogosphere, I wanted to point out a much faster method for testing monitoring of CentOS 5.x when you are learning and experimenting in your non-production scenarios. Truly I hope MS is someday able to provide support for CentOS and OpenSolaris in particular, as I think these platforms are widely used by developers and somewhat more predictable in their similarities to their commercial counterparts.
How Similar are Red Hat Enterprise Linux (RHEL) 5 and CentOS?
For anyone that may not be aware, Red Hat releases all source code for the product publicly under the terms of the GNU General Public License and other licenses. CentOS developers use that source code to create a final product that is very similar to RHEL; the logos must be changed, because Red Hat does not allow them to be used for redistribution. If you look at the release dates, you will notice CentOS releases come very quickly behind their Red Hat counterparts, generally within 4-5 weeks, as shown HERE. In short, while there is no guarantee of their ultimate similarity, Red Hat and CentOS are in the end very similar at present.
Discovering and Monitoring CentOS
As mentioned, I've seen posts on unsealing management packs, etc., and wanted to point out the "easy button" method for this. If you look at the Microsoft.Linux.RHEL.5 MP, you'll see the discovery for RHEL systems involves a simple query to the CIM Namespace root/scx to find the "Caption" of the operating system (basically a display name).Clearly this will be very different on a CentOS server versus a Red Hat server. However, this is easily changed for testing purposes, with no ill effects that we have yet been able to identify after several days.
Changing the OS Caption on a CentOS Server.
This value is stored in the /etc/redhat-release file. In fact, this Caption is the only value stored in this file. So, first make a backup of this file. The value present on a CentOS system will be something similar toCentOS release 5 (final). If you change this value to reflect the value on a standard RHEL 5 or 5.1 system. I used Red Hat Enterprise Linux Server release 5.1 (Tikanga), which I pulled straight from the redhat-release file on an RHEL 5.1 system. This changes the value returned for the OS Caption when the root/scx namespace is queried by the object discovery, as well as how the Unix and Linux Computer Management Wizard identifies the target computer.
Results
After making this change, I ran the Unix and Linux Computer Management Wizard and successfully pushed an agent to the server. Within a couple of hours, the same discovery, monitoring and performance collection data present for my RHEL 5.1 server also seemed to be working for my CentOS server - another testament to the similarity of the two. As for production scenarios, I am taking a wait-and-see attitude in hopes that we'll see some unofficial guidance from the product team at some point down the road.