Explicit active-passive failover (ALUA) mode using dm-multipath on EMC Clariion storage is now available. This mode is provided as per T10 specifications, but is provided in this release only as a technology preview.

For more information about T10, refer to http://www.t10.org.

The latest generation of the ext filesystem, ext4, is available in this release as a Technology Preview. Ext4 is an incremental improvement on the ext3 file system developed by Red Hat and the Linux community. The release name of the file system for the Technology Preview is ext4dev.

The file system is provided by the ext4dev.ko kernel module, and a new e4fsprogs package, which contains updated versions of the familiar e2fsprogs administrative tools for use with ext4. To use, install e4fsprogs and then use commands like mkfs.ext4dev from the e4fsprogs program to create an ext4-base file system. When referring to the filesystem on a mount commandline or fstab file, use the filesystem name ext4dev.

FreeIPMI is now included in this update as a Technology Preview. FreeIPMI is a collection of Intelligent Platform Management IPMI system software. It provides in-band and out-of-band software, along with a development library conforming to the Intelligent Platform Management Interface (IPMI v1.5 and v2.0) standards.

For more information about FreeIPMI, refer to http://www.gnu.org/software/freeipmi/

TrouSerS and tpm-tools are included in this release to enable use of Trusted Platform Module (TPM) hardware.TPM hardware features include (among others):

TrouSerS is an implementation of the Trusted Computing Group's Software Stack (TSS) specification. You can use TrouSerS to write applications that make use of TPM hardware. tpm-tools is a suite of tools used to manage and utilize TPM hardware.

For more information about TrouSerS, refer to http://trousers.sourceforge.net/.

eCryptfs is a stacked cryptographic file system for Linux. It mounts on individual directories in existing mounted lower file systems such as EXT3; there is no need to change existing partitions or file systems in order to start using eCryptfs.

With this release, eCryptfs has been re-based to upstream version 56, which provides several bug fixes and enhancements. In addition, this update provides a graphical program to help configure eCryptfs (ecryptfs-mount-helper-gui).

This update also changes the syntax of certain eCryptfs mount options. If you choose to update to this version of eCryptfs, you should update any affected mount scripts and /etc/fstab entries. For information about these changes, refer to man ecryptfs.

The following caveats apply to this release of eCryptfs:

For more information about eCryptfs, refer to http://ecryptfs.sf.net. You can also refer to http://ecryptfs.sourceforge.net/README and http://ecryptfs.sourceforge.net/ecryptfs-faq.html for basic setup information.

Stateless Linux is a new way of thinking about how a system should be run and managed, designed to simplify provisioning and management of large numbers of systems by making them easily replaceable. This is accomplished primarily by establishing prepared system images which get replicated and managed across a large number of stateless systems, running the operating system in a read-only manner (refer to /etc/sysconfig/readonly-root for more details).

In its current state of development, the Stateless features are subsets of the intended goals. As such, the capability remains as Technology Preview.

Red Hat recommends that those interested in testing stateless code read the HOWTO at http://fedoraproject.org/wiki/StatelessLinux/HOWTO and join stateless-list@redhat.com.

The enabling infrastructure pieces for Stateless Linux were originally introduced in Red Hat Enterprise Linux 5.

AIGLX is a Technology Preview feature of the otherwise fully supported X server. It aims to enable GL-accelerated effects on a standard desktop. The project consists of the following:

By installing these components, you can have GL-accelerated effects on your desktop with very few changes, as well as the ability to enable and disable them at will without replacing your X server. AIGLX also enables remote GLX applications to take advantage of hardware GLX acceleration.

The Linux target (tgt) framework allows a system to serve block-level SCSI storage to other systems that have a SCSI initiator. This capability is being initially deployed as a Linux iSCSI target, serving storage over a network to any iSCSI initiator.

To set up the iSCSI target, install the scsi-target-utils RPM and refer to the instructions in:

Replace [version] with the corresponding version of the package installed.

For more information, refer to man tgtadm.

The firewire-sbp2 module is still included in this update as a Technology Preview. This module enables connectivity with FireWire storage devices and scanners.

At present, FireWire does not support the following:

In addition, the following issues still exist in FireWire:

This release includes ktune (from the ktune package), a service that sets several kernel tuning parameters to values suitable for specific system profiles. Currently, ktune only provides a profile for large-memory systems running disk-intensive and network-intensive applications.

The settings provides by ktune do not override those set in /etc/sysctl.conf or through the kernel command line. ktune may not be suitable on some systems and workloads; as such, you should test it comprehensively before deploying to production.

You can disable any configuration set by ktune and revert to your normall settings by simply stopping the ktune service using service ktune stop (as root).

Serial General Purpose Input Output (SGPIO) is an industry standard communication method used between a main board and a variety of internal and external hard disk drive bay enclosures. This method can be used to control LED lights on an enclosure through the AHCI driver interface.

In this release, SGPIO support in dmraid is included as a technology preview. This will allow dmraid to work properly with disk enclosures.

The Gnu Compiler Collection version 4.3 (GCC4.3) is now included in this release as a technology preview. This collection of compilers include C, C++, and Fortran 95 compilers along with support libraries.

Note that in the gcc43 packages, the default for the gnu89-inline option has been changed to -fgnu89-inline, whereas upstream and future updates of Red Hat Enterprise Linux 5 will default to -fno-gnu89-inline. This is necessary because many headers shipped as part of Red Hat Enterprise Linux 5 expect GNU in-line semantics instead of ISO C99 semantics. These headers have not been adjusted to request GNU in-line semantics through attributes.