CentOS 5.2 Tutorials CentOS 5.3 Tutorials CentOS 5.4 Tutorials CentOS 5.5 Tutorials

CentOS: The most popular Linux distribution for web servers

It’s a great day for CentOS and its community because, according to Web Technology Surveys, in July 2010, “For the first time, CentOS is now leading the Linux distribution statistics on web servers with almost 30% of all Linux servers.”

CentOS Webserver survey

Read more at W3Techs

CentOS 5.4 Tutorials

ASSP (Anti-Spam SMTP Proxy) On CentOS 5.4 part 2

This is a follow up post to Fight Spam With #ASSP (Anti-Spam SMTP Proxy) On CentOS 5.4. If you haven’t already installed ASSP do so before continuing with this How To and remember that you need a working installation of Microsoft Exchange 2007 Server as well. This How To can be implemented on a live Microsoft Exchange 2007 server while it’s running. Leave the original ports (25 In and 25 Out, OWA and/or internal usage ports) alone and create new ones. Once you’re ready to go simply activate the new ports, then deactivate the original ports, your users will never see a glitch in service and will make rolling back just as seamless.

Preliminary Note:

I am using a CentOS 5.4 i386 base installation with ASSP (Anti-Spam SMTP Proxy) and Microsoft Exchange 2007 Server already installed and configured in this tutorial.

* (IP CentOS 5.4 i386 ASSP installation
* (IP Microsoft Exchange 2007 server

CentOS 5.4 Tutorials

Fight Spam: ASSP (Anti-Spam SMTP Proxy) On CentOS 5.4

The Anti-Spam SMTP Proxy (ASSP) server project is an Open Source, Perl based, platform-independent transparent SMTP proxy server that leverages numerous methodologies and technologies to both rigidly and adaptively identify e-mail spam. ASSP is easy to set up because it requires only minor changes to the configuration of your your Mail Transfer Agent.

Also please read the ASSP documentation

Preliminary Note

In this tutorial I use a base 32 bit server install with the hostname with the IP address These settings might differ for you, so you have to replace them where appropriate.

Adjust any package names if installing the EL4 or 64 bit packages. If any dependencies are unsatisfied, install the required packages and retry

CentOS 5.2 Tutorials

Remus applied to the official Xen repository

The one problem with Xen is transparent high availability of your servers, sure you can snapshot an image but thats only of you shutdown the virtual machine. How excited was I when Remus announced that it has been applied to the official Xen repository, and is expected to be included with the next major release. Bookmark this page for a soon to be released how to install Xen with Remus support on CentOS 5.4!

What is Remus?

Remus provides transparent, comprehensive high availability to ordinary virtual machines running on the Xen virtual machine monitor. It does this by maintaining a completely up-to-date copy of a running VM on a backup server, which automatically activates if the primary server fails. Key features:

* The backup VM is an exact copy of the primary VM. When failure happens, it continues running on the backup host as if failure had never occurred.
* The backup is completely up-to-date. Even active TCP sessions are maintained without interruption.
* Protection is transparent. Existing guests can be protected without modifying them in any way.

For a full description and evaluation, see their NSDI paper.

Visit the project: