What's new in Red Hat Enterprise Linux 5.6
by Thorsten Leemhuis
The official features that Red Hat has added to the revised Enterprise Linux 5.6 include the Ext4 file system. Other innovations include fresher versions of Bind and PHP, along with a number of revised drivers to improve support for current hardware.
Version 6 of Red Hat Enterprise Linux (RHEL) has been Red Hat's flagship product since it was released in mid-November. However, the previous series is still in service and has a way to go before its EOL (March 2014), as version 5.6, released yesterday, illustrates. The latest release of series 5 includes some of the technologies found in RHEL6.
Full support for Ext4 file system
Older RHEL5 versions already included Ext4 as an unsupported "Technical Preview", but the standard file system in RHEL6 is now also fully supported in version 5.6. Used for more than a year in a number of desktop distributions, such as Fedora and Ubuntu, Ext4 offers a number of advantages, such as more efficient storage with the use of extents, faster checks of file systems than in Ext3, more robust journaling and support for large file systems.
Version 9.7 of the Bind name server, which provides better support for DNSsec, is also part of packages whose names start with "bind97-". Older RHEL5 versions that include Bind 9.3 have the prefix "bind-" and are still part of RHEL to give users the option of keeping the old version of the name server. Red Hat uses the same trick for PHP. In packages starting with "php-", PHP 5.1.6 is still used, whereas RHEL 5.6 has the new PHP 5.3.2 in packets beginning with "php53-".
For the first time, version 5.6 of RHEL5 includes ebtables (Ethernet bridge tables) – a firewall tool for the transparent filtering of network traffic over a bridge. Another innovation is the System Security Services Daemon (SSSD), which offers a number of services for the central management of identity and authentication. Versions 3.0.33 ("samba") of Samba and the updated 3.5.4 ("samba3x") are also included. The latter offers expanded LDAP support and also supports Winbind over IPv6. OpenJDK has now caught up with IcedTea 1.7.5, which reportedly improves the performance and stability of the JIT compiler Hotspot.
The virtualisation API libvirt has jumped from 0.6.3 to version 0.8.2, which offers many more functions. RHEL 5.6 therefore now also supports RHEL6’s sVirt (SELinux virtualisation) to isolate guest systems.
A number of firms and projects are working on clones of RHEL. The most popular one is the free-of-charge CentOS, which promises complete compatibility with RHEL – which is why CentOS does not normally include any functions that RHEL does not have, unlike Scientific Linux.
Usually, the next version of CentOS is released some 45 to 90 days after the latest RHEL version; for instance, CentOS 5.5 was released six weeks after RHEL 5.5, while CentOS appeared seven weeks after the previous version of RHEL. It may take a bit longer this time, however, because the developers of CentOS are still working on CentOS 6.0. According to a tweet posted a week ago by the CentOS developers, it will be a few more weeks before the successor to RHEL 6.0, which was released in November, is published.
Improved hardware support
As usual, Red Hat has expanded hardware support. As with Bind and PHP, the new versions of printer and scanner drivers for HP devices are included in a package called hplip3 so that you do not have to switch to the new drivers if you don't want to. The new RHEL version also supports the Cintiq 21UX2 graphics tablet from Wacom and reportedly also works better with modern sound chips, thanks to updated HD Audio ALSA drivers.
The drivers for network and storage hardware have also been comprehensively updated and expanded; for details, see the section in the Release Notes. In addition, Red Hat has expanded support in Intel graphics drivers for the graphics kernels used in the Core i3 / i5 processors, introduced at the beginning of last year. Support has also reportedly been improved for AMD's latest processors.
The Release Notes provide an overview of these and other changes in RHEL 5.6. The 5.6 Technical Notes on the new version are even more detailed. For instance, the section on Anaconda covers a number of changes that affect the installer, such as support for 10G LAN chips from Brocade, Chelsio and QLogic. Section 3.1 also explains some aspects in the interplay between RHEL and disks with 4K sectors. Administrators should read this section so they can obtain optimal performance from their drives.
Up to the end of the year, RHEL5 will still be in the first phase of the RHEL life cycle, so the next version will probably also include major changes. In subsequent phases, the changes are always fewer and less far-reaching, so you should expect to have to switch to RHEL6 in a year or two if you want support for the latest hardware. In blogs and Bugzilla posts, it already seems clear that Red Hat is busy working on RHEL 6.1, although it will probably be a few months before we see it.