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7. Technology Previews

Technology Preview features are currently not supported under Red Hat Enterprise Linux subscription services, may not be functionally complete, and are generally not suitable for production use. However, these features are included as a customer convenience and to provide the feature with wider exposure.
Customers may find these features useful in a non-production environment. Customers are also free to provide feedback and functionality suggestions for a Technology Preview feature before it becomes fully supported. Erratas will be provided for high-severity security issues.
During the development of a Technology Preview feature, additional components may become available to the public for testing. It is the intention of Red Hat to fully support Technology Preview features in a future release.
ALUA Mode on EMC Clariion
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
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
TrouSerS and tpm-tools
TrouSerS and tpm-tools are included in this release to enable use of Trusted Platform Module (TPM) hardware.TPM hardware features include (among others):
  • Creation, storage, and use of RSA keys securely (without being exposed in memory)
  • Verification of a platform's software state using cryptographic hashes
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
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:
  • Note that the eCryptfs file system will only work properly if the encrypted file system is mounted once over the underlying directory of the same name. For example:
    mount -t ecryptfs /mnt/secret /mnt/secret
    The secured portion of the file system should not be exposed, i.e. it should not be mounted to other mount points, bind mounts, and the like.
  • eCryptfs mounts on networked file systems (e.g. NFS, Samba) will not work properly.
  • This version of the eCryptfs kernel driver requires updated userspace, which is provided by ecryptfs-utils-56-4.el5 or newer.
For more information about eCryptfs, refer to You can also refer to and for basic setup information.
Stateless Linux
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 and join
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:
  • A lightly modified X server.
  • An updated Mesa package that adds new protocol support.
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 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:
  • IPv4
  • pcilynx host controllers
  • multi-LUN storage devices
  • non-exclusive access to storage devices
In addition, the following issues still exist in FireWire:
  • a memory leak in the SBP2 driver may cause the machine to become unresponsive.
  • a code in this version does not work properly in big-endian machines. This could lead to unexpected behavior in PowerPC.
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).
SGPIO Support for dmraid
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.
GCC 4.3
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.
Kernel Tracepoint Facility
In this update, a new kernel marker/tracepoint facility has been implemented as a Technology Preview. This interface adds static probe points into the kernel, for use with tools such as SystemTap.
Device Failure Monitoring of RAID sets
Device Failure Monitoring, using the tools dmraid and dmevent_tool, is included in Red Hat Enterprise Linux 5.3 as a Technology Preview. This provides the ability to watch and report device failures on component devices of RAID sets.

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