After 6 plus years of service, Red Hat is moving its Red Hat Enterprise Linux 4 (RHEL 4) into a bug and security fix maintenance phase. The move follows the release of RHEL 4.9 which is the last update of RHEL 4.x that will include new features and hardware support.
According to Red Hat, RHEL 4.9 included 200 updates including an update version of SystemTap.
RHEL 4 was first released back in 2005 and was the first version of RHEL to be released after Red Hat discontinued its Red Hat Linux line (which has since transitioned to become the community Fedora Linux distro).
RHEL 4 also marked the debut of SELinux which has been significantly enhanced over the years to be both more usable and powerful to secure enterprises. RHEL 4 was also the first version RHEL to have the 2.6 Linux kernel.