CentOS team recently prepared and released new versions of CentOS with number of fixes and improvements. New versions are 5.9 and 6.4. We have older versions installed on some of our Linux servers.
We are going to perform OS upgrade on these servers. In addition to the upgrade during this maintenance window, we are going to apply new, strict firewall rules. This firewall will block certain types of attacks, therefore imporving servers stability and security level.
Furthermore, we will need to reboot the servers to apply and effect the updates. Expected downtime is 5-15 minutes/server. However, some of servers may require FSCK (Linux requires FSCK after certain number of reboots), for these ones the expected downtime can be extended up to 1 hour.
If you have any questions, please contact us at firstname.lastname@example.org