Today another update release of RHEL5 was born.

These (minor) update releases typically provide feature enhancements, bugfixes and new hardware support. And as such come as a set of new installation media (CDs and DVD). We already discussed the RHEL 5.5 Beta release not so long ago, and apart from stabilizing the product, a lot of what was known from that Beta is true for the real RHEL 5.5 release.

From the release notes:

Highlights of the Red Hat Enterprise Linux 5.5 release include hardware enablement for the Intel Boxboro-EX platform, AMD Magny-Cours processor and IBM Power 7 processor. Virtualization is improved, with support for multiple 10 GigE SR-IOV cards, and automatic usage of hugepages for virtual guest memory when enabled on the system. Interoperability improvements include updates to OpenOffice for Microsoft Office 2007 filters, Samba for Windows 7 compatibility and boot support for virtual machines using Microsoft based PXE services.

But our own summary of technical details would highlight:

* Kickstart improvements to logging post-install

* New hardware driver support (pmcraid, ibmvfs, bfa, be2iscsi)

* Updated hardware support (too many to list, but includes wireless driver rebase)

* Support for Intel's Boxboro-EX and Boxboro-MC, AMD's Magny-Cours and IBM's Power7 processor

* Run-time memory allocation for KVM guests (memory ballooning)

* PCI passthrough improvements (hotswapping PCI devices, 1:1 performance improvements)

* Detecting kernel tasks stuck in the uninterruptible sleep state (D-state)

* Improved CFQ I/O scheduler performance

* Kernel CIFS updates and new GFS mount option (for troubleshooting)

* GDB, Valgrind and Systemtap updates for improved debugging

* Software updates (openoffice, metacity, samba, freeradius)

Apart from this Red Hat also shared Technology Previews within each release. Functionality that is not yet supported, but available for testing purposes:

* FCoE (Fibre Channel over Ethernet)

* ext4 filesystem support

* gcc 4.4 and new glibc malloc

* Trusted Platform Module (TPM) hardware support

* eCryptfs cryptographic filesystem

* FreeIPMI

* Stateless Linux

* SGPIO Support for dmraid

* Device Failure Monitoring of RAID sets

* iSER support (block storage transfer across a network)

Which means that the above Technology Preview features of RHEL5.5 may become part of a future RHEL5 release !

Even though there is no predicted timeline for CentOS releases, CentOS 5.5 is not expected before May 4th 2010 (5 weeks).

Update: After the public release announcement I modified this article to reflect this.