Included in this release of Red Hat Enterprise Linux 5 are enabling infrastructure pieces for Stateless Linux. Stateless Linux is a new way of thinking about how a system is to 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 (please 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 is being labeled as a technology preview.

The following is a list of the initial capabilities included in Red Hat Enterprise Linux 5:

It is highly recommended that those interested in testing stateless code read the HOWTO at http://fedoraproject.org/wiki/StatelessLinuxHOWTO and join [email protected].

GFS2 is an evolutionary advancement based on the GFS file system. While fully functional, GFS2 is not yet considered production-ready. GFS2 is targeted to become fully supported in a subsequent Red Hat Enterprise Linux 5 update. There is also an in-place conversion utility, gfs2_convert, which can update the metadata of the older GFS file system format, converting it to a GFS2 file system.

FS-Cache is a local caching facility for remote file systems that allows users to cache NFS data on a locally mounted disk. To set up the FS-Cache facility, install the cachefilesd RPM and refer to the instructions in /usr/share/doc/cachefilesd-<version>/README.

Replace <version> with the corresponding version of the cachefilesd package installed.

Red Hat Enterprise Linux 5 features a technology preview of Xen-based virtualization capabilities for IA64, as well as the software infrastructure needed to manage a virtualized environment.

The implementation of Virtualization in Red Hat Enterprise Linux 5 is based on the hypervisor, which facilitates extremely low overhead virtualization through paravirtualization. With Intel VT-I capable processors, virtualization in Red Hat Enterprise Linux 5 also allows operating systems to run unmodified in fully virtualized mode.

Virtualization on Red Hat Enterprise Linux 5 also features the following:

To install the Virtualization feature, you need to use the linux debug parameter when initializing Anaconda.

Virtual machines can also be managed through Red Hat Network.

At present, the Virtualization feature has the following limitations:

Compiz is an OpenGL-based compositing window manager. In addition to regular window management, compiz also acts as a compositing manager, coordinating and synchronizing the overall desktop redrawing to provide a smoother desktop experience with less flicker.

Compiz uses 3D hardware acceleration to render effects such as live thumbnail windows, window drop shadows, animated window minimizing and transitions between virtual desktops.

Due to limitations in the current rendering architecture, compiz cannot work correctly with direct rendering OpenGL applications or applications using the Xv extension. Such applications will exhibit harmless rendering artifacts; because of this, compiz is currently a technology preview.

In Red Hat Enterprise Linux 5, the EXT3 file system capacity has been extended beyond 8TB to a maximum of 16TB. This capability is being included as a technology preview, and is targeted for full support in a future release of 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 goal of the frysk project is to create an intelligent, distributed, always-on system monitoring and debugging tool that allows developers and system administrators to:

In Red Hat Enterprise Linux 5 the frysk graphical user interface is a technology preview, whereas the frysk command line interface is fully supported.

Systemtap provides free software (GPL) infrastructure to simplify the gathering of information about the running Linux system. This assists diagnosis of a performance or functional problem. With the help of systemtap, developers no longer need to go through the tedious and disruptive instrument, recompile, install, and reboot sequence that may be otherwise required to collect data.

Dogtail is a GUI test tool and automation framework written in Python that uses Accessibility technologies to communicate with desktop applications.

Red Hat Enterprise Linux 5 also features support for the following languages as technology preview:

For more information about how to install and enable support for these languages, refer to the Internationalization section of this document.

Anaconda now has the capability to detect, create, and install to dm-multipath devices. To enable this feature, add the parameter mpath to the kernel boot line.

Note that the parameter mpath may cause a boot failure if a device's major:minor number changes. This issue will be addressed in a future update of Red Hat Enterprise Linux 5.

Anaconda now provides the ability to install to an iSCSI device. Booting and installing is fully supported with the QLogic qla4xxx hardware initiator. However, the capability to install to an iSCSI device for the open-iscsi software initiator is currently considered a Technology Preview, due to the following issues:

These limitations will be addressed in a future Red Hat Enterprise Linux 5 update.

This release of Red Hat Enterprise Linux includes a fairly comprehensive Deployment Guide. To access it, go to System (on the top panel) => Documentation => Red Hat Enterprise Linux Deployment Guide.

It is the intention of Red Hat to provide fully localized versions of the Deployment Guide for all supported languages. If you have installed a localized version of the Deployment Guide, it is recommended that you update it when a new version becomes available through Red Hat Network.

Red Hat Enterprise Linux 5 now includes version 2.2 of the Apache HTTP Server. This release brings a number of improvements over the 2.0 series, including:

The following changes have been made to the default httpd configuration:

If you are upgrading from a previous release of Red Hat Enterprise Linux, the httpd configuration will need to be updated for httpd 2.2. For more information, refer to http://httpd.apache.org/docs/2.2/upgrading.html.

Note that any third-party modules compiled for httpd 2.0 must be rebuilt for httpd 2.2.

Version 5.1 of PHP is now included in Red Hat Enterprise Linux 5, which includes a number of changes to the language along with significant performance improvements. Some scripts might need to be edited for use with the new version; please refer to the link below for more information on migrating from PHP 4.3 to PHP 5.1:

http://www.php.net/manual/en/migration5.php

The /usr/bin/php executable is now built using the CLI command-line SAPI, rather than the CGI SAPI. Use /usr/bin/php-cgi for CGI SAPI. The php-cgi executable also includes FastCGI support.

The following extension modules have been added:

The following extension modules are no longer included:

The PEAR framework is now packaged in the php-pear package. Only the following PEAR components are included in Red Hat Enterprise Linux 5:

Red Hat Enterprise Linux 5 now provides basic support for encrypted swap partitions and non-root file systems. To use these features, add the appropriate entries to /etc/crypttab and reference the created devices in /etc/fstab.

Below is a sample /etc/crypttab entry:

my_swap /dev/hdb1 /dev/urandom swap,cipher=aes-cbc-essiv:sha256

This creates the encrypted block device /dev/mapper/my_swap, which can be referenced in /etc/fstab.

Below is a sample /etc/crypttab entry for a file system volume:

my_volume /dev/hda5 /etc/volume_key cipher=aes-cbc-essiv:sha256

The /etc/volume_key file contains a plaintext encryption key. You can also specify none as the key file name; this configures the system to ask for the encryption key during boot instead.

It is recommended to use LUKS (Linux Unified Key Setup) for setting up file system volumes. To do this, follow these steps:

The mount and umount commands no longer directly support NFS; a built-in NFS client no longer exists. A separate nfs-utils package, which provides /sbin/mount.nfs and /sbin/umount.nfs helpers, must be installed for this.

CUPS printer browsing over a local subnet can be configured using the graphical tool system-config-printer. It can also be done using the CUPS web interface, http://localhost:631/.

To use directed broadcasts for printer browsing between subnets, open /etc/cups/cupsd.conf on the clients and replace BrowseAllow @LOCAL with BrowseAllow ALL.

ATI graphics cards based on the R500 chipset are supported for the vesa driver only, and are not supported by Red Hat Enterprise Linux 5 on external monitors, LCD projectors or accelerated 3D support.

up2date is being deprecated in favor of yum (Yellowdog Updater Modified). As such, it is advisable that you revise any up2date-dependent scripts your system is using accordingly. For more information about yum, consult its man page with the command man yum; you can also consult the installed documentation under the directories /usr/share/doc/yum-<version> and /usr/share/doc/yum-metadata-parser-<version> (replace <version> with the corresponding version of yum and yum-metadata-parser installed).

Red Hat Directory Server is an LDAP-based server that centralizes enterprise and network data into an OS-independent, network-based registry. It is set to replace OpenLDAP server components, which will be deprecated after Red Hat Enterprise Linux 5. For more information about Red Hat Directory Server, refer to http://www.redhat.com/software/rha/directory/.

The i810 driver supports all integrated Intel graphics chipsets, from i810 to i965. However, the support for i830 (and newer) chipsets is limited; the i810 driver can only set modes listed in the video BIOS. If your machine has an i830 or newer chipset installed, run the following command to determine what the available modes are:

grep Mode: /var/log/Xorg.0.log

Modes marked with an asterisk (*) are available for selection.

Many laptop video BIOSes do not supply a mode that matches the native panel size. Therefore the chosen mode may appear stretched, distorted, or with black borders. As such, if your chosen mode does not display properly, you need a BIOS update from your hardware vendor for the native panel size to work correctly.

This release of Red Hat Enterprise Linux 5 includes support for the ipw3945 (Intel PRO/Wireless 3945ABG Network Connection) adapter. The Red Hat Enterprise Linux 5 Supplementary disc contains the driver, regulatory daemon and firmware needed to support this adapter.

To enable support for the ipw3945 wireless adapter, search the Red Hat Enterprise Linux 5 Supplementary disc for packages with filenames containing "3945" and install them.

rawio is a deprecated interface; however, Red Hat Enterprise Linux 5 still includes support for it. If you have an application that performs device access using rawio, it is highly recommended that you modify your application to open the block device with the O_DIRECT flag. The rawio interface will remain throughout the life of Red Hat Enterprise Linux 5, but is a candidate for removal in a future release.

Currently, AIO (Asynchronous I/O) on file systems is only supported in O_DIRECT or non-buffered mode. Further, note that the asynchronous poll interface is no longer present, and that AIO on pipes is no longer supported.

ctmpc is a deprecated driver; however, it will still be included throughout the life of Red Hat Enterprise Linux 5. Note that it is a candidate for removal from future releases.

Red Hat Enterprise Linux 5 now supports policy modules and semanage. Policy modules simplify the creation and distribution of policy customizations and third-party policies through the use of the semodule and checkmodule tools.

The semanage tool is a policy management tool that modifies the SELinux configuration. It also allows you to configure file contexts, networking component labeling, and user mappings for Linux-to-SELinux.

The raw devices interface has been deprecated in Red Hat Enterprise Linux 5; raw device mapping is now configured via udev rules.

To configure raw device mapping, add the appropriate entries to /etc/udev/rules.d/60-raw.rules in the following formats:

Replace <device name> with the name of the device you need to bind (for example, /dev/sda1). "A" and "B" are the major / minor numbers of the device you need to bind, and X is the raw device number that you want the system to use.

If you have a large, pre-existing /etc/sysconfig/rawdevices file, convert it with the following script:

#!/bin/sh

grep -v "^ *#" /etc/sysconfig/rawdevices | grep -v "^$" | while read dev major minor ; do
	if [ -z "$minor" ]; then
		echo "ACTION==\"add\", KERNEL==\"${major##/dev/}\", RUN+=\"/usr/bin/raw $dev %N\""
	else
		echo "ACTION==\"add\", ENV{MAJOR}==\"$major\", ENV{MINOR}==\"$minor\", RUN+=\"/usr/bin/raw $dev %M %m\""
	fi
done

Red Hat Enterprise Linux 5 supports the QLogic family of iSCSI HBA (Host Bus Adapters). At present, only the iSCSI interface to these boards are supported (using the qla4xxx driver).

In addition, Red Hat does not currently support these boards as Ethernet NIC, as this capability requires the qla3xxx driver. This issue will be addressed in an upcoming minor release of Red Hat Enterprise Linux 5.

In order to optimally exploit the IBM System z instruction set for 31-bit applications, it is recommended that you use the gcc option -march=z900. For 64-bit applications, the gcc will exploit the IBM System z instruction set by default.

The iSeries ODBC Driver for Linux has been replaced by the iSeries Access for Linux, which can be downloaded at the following link:

http://www.ibm.com/eserver/iseries/access/linux/

The iSeries Access for Linux offers Linux-based access to iSeries servers, and allows you to:

Red Hat Enterprise Linux no longer supports the IBM Power4 iSeries.

kdump reserves a significant amount of memory at boot time, which changes the actual minimum memory requirements of Red Hat Enterprise Linux 5. To compute the actual minimum memory requirements for your system, refer to http://www.redhat.com/rhel/details/limits/ for the listed minimum memory requirements; then, add the amount of memory used by kdump to determine the actual minimum memory requirements.

On Red Hat Enterprise Linux 5, it is possible to build updated kernel module packages that depend upon the current kernel ABI version and not on a specific kernel release number. This facilitates building kernel modules that can be used against a range of Red Hat Enterprise Linux 5 kernels, rather than a single release. The project website at http://www.kerneldrivers.org/ contains more information about the packaging process, as well as several examples.

Note that the following issues have also been identified:

These issues will be addressed in a future update of Red Hat Enterprise Linux 5.

The module loading behavior on Red Hat Enterprise Linux 5 has changed from previous releases of Red Hat Enterprise Linux. The modules shipped in the Red Hat Enterprise Linux 5 kernel package are signed, as was the case in Red Hat Enterprise Linux 4. On Red Hat Enterprise Linux 5 kernels, however, it is no longer possible to load a signed module from another kernel build.

This means that a module shipped with the initial Red Hat Enterprise Linux 5 distribution cannot be loaded in future updated kernels. This helps prevent users from loading unsupported modules on a system. Red Hat only supports modules that are signed and included in a distribution.

If you want to load an older module, you can try rebuilding it without a signature. Alternatively, you can remove the signature from the binary file using the following command:

objcopy -R .module_sig <module name>-mod.ko <module name>-nosig.ko

It is recommended that you consult with a designated Red Hat Global Support Representative before attempting to load unsigned modules.

SCIM (Smart Common Input Method) has replaced IIIMF as the input method system for Asian and other languages in this release. The default GTK Input Method Module for SCIM is provided by scim-bridge; in Qt, it is provided by scim-qtimm.

Below are the default trigger hotkeys for different languages:

If SCIM is installed, it runs by default for all users.

After installing or removing SCIM engine packages, it is recommended to start a new desktop session in order for the changes to be reflected in the SCIM language menu.

To enable additional language support for some Asian languages, you need to install the necessary language support packages. Below is a list of these languages and the command you need to run (as root) to install their corresponding language support packages:

It is also recommended that you install scim-bridge-gtk and scim-qtimm when enabling additional language support. The scim-bridge-gtk package prevents possible binary conflicts with third-party applications linked against older versions of libstdc++.

Note that additional language support packs are also available for OpenOffice (openoffice.org-langpack-<language code>_<locale>) and KDE (kde-i18n-<language>). These packages can also be installed through yum.

A new user configuration tool called im-chooser has been added, which allows you to easily disable or enable the usage of input methods on your desktop. So if SCIM is installed but you do not wish to run it on your desktop, you can disable it using im-chooser.

At X startup, xinput.sh now sources ~/.xinputrc or /etc/X11/xinit/xinputrc instead of searching config files under ~/.xinput.d/ or /etc/xinit/xinput.d/.

Firefox in Red Hat Enterprise Linux 5 is built with Pango, which provides better support for certain scripts, such as Indic and some CJK scripts.

To disable the use of Pango, set MOZ_DISABLE_PANGO=1 in your environment before launching Firefox.

Support is now available for synthetic emboldening of fonts that do not have a bold face.

New fonts for Chinese have been added: AR PL ShanHeiSun Uni (uming.ttf) and AR PL ZenKai Uni (ukai.ttf). The default font is AR PL ShanHeiSun Uni, which contains embedded bitmaps. If you prefer outline glyphs, add the following section to your ~/.font.conf file:

<fontconfig>
  <match target="font">
    <test name="family" compare="eq">
      <string>AR PL ShanHeiSun Uni</string>
    </test>
    <edit name="embeddedbitmap" mode="assign">
      <bool>false</bool>
    </edit>
  </match>
</fontconfig>				
			

The Gtk2 context menu IM submenu no longer appears by default. You can enable it on the command line with the following command:

gconftool-2 --type bool --set '/desktop/gnome/interface/show_input_method_menu' true

CJK (Chinese, Japanese, and Korean) rendering support has been removed from the Anaconda text installation. The text installation method is being deprecated in the long term, as the GUI installation, VNC and kickstart methods are preferred.

The following packages are deprecated and scheduled for removal in Red Hat Enterprise Linux:

These packages are being deprecated in favor of the gtk2 stack, which offers better functionality particularly in terms of internationalization and font handling.

If you need to display Chinese, Japanese, or Korean text on the console, you need to set up a framebuffer; afterwards, install bogl-bterm, and run bterm on the framebuffer.