I was recently introduced to CentOS 4.0, which is a Linux distribution built from the source RPMs that comprise Redhat Advanced Server. I am currently running several production services on CentOS 4.0, and am extremely happy with the features it brings to the table. Here are several reasons you might be interested in using CentOS:
1. CentOS 4.0 is free, and has the look and feel of Redhat Advanced Server. If you are used to managing servers running one of the Redhat derivatives, you will feel right at home.
2. CentOS 4.0 uses yum as the default package manager!
3. CentOS mirrors the upstream RPMS provided by Redhat, and offers several additional repositories ( e.g., extras, addons, contribs, centosplus, etc.) to extend the base CentOS installation.
4. The CentOS team will provide security updates for CentOS 4.0 until February 29, 2012.
5. CentOS is supposed (I haven’t tested this yet) to be binary compatible with Redhat Advanced Server. This can lower costs for companies that don’t need true parity between production, QE, test and development servers.
6. Redhat Advanced Server is widely deployed, and there are dozens of places to get free support for it. Since CentOS is identical to Redhat Advanced Server, you can use the Redhat support forums to find answers to your questions.
7. Redhat Advanced Server is running some large websites, and you can be assured that corporate customers are leveraging their support contracts to get problems fixed. These fixes turn up in CentOS 4.0, so you benefit for free.
8. You can use Redhat Global File System 6.1 and Cluster Suite 4.0 with CentOS 4.0.
If you are looking for a commercially supported Linux distribution, CentOS is probably not for you. But if you want to use a distribution that is super reliable and community supported, it might be the right distribution for you.