5.2 Release Notes

Red Hat Enterprise Linux 5

Release Notes for Red Hat Enterprise Linux 5.2

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Don Domingo

Engineering Services and Operations Content Services

Abstract

The Release Notes provide high-level coverage of the improvements and additions that have been implemented in Red Hat Enterprise Linux 5.2. For detailed documentation on all changes to Red Hat Enterprise Linux for the 5.2 update, refer to the Technical Notes.

1. Release Notes Updates

This section contains information about Red Hat Enterprise Linux 5.2 that did not make it into the Release Notes included in the distribution.

1.1. All Architectures

  • Thin Provisioning (also known as "virtual provisioning") will be first released with EMC Symmetrix DMX3 and DMX4. Please refer to the EMC Support Matrix and Symmetrix Enginuity code release notes for further details.
  • dom0 has a system-wide IRQ (interrupt request line) limit of 256, which is consumed as follows:
    • 3 per physical CPU.
    • 1 per guest device (i.e. NIC or block device)
    When the IRQ limit is reached, the system will crash. As such, check your IRQ consumption to make sure that the number of guests you create (and their respective block devices) do not exhaust the IRQ limit.
    To determine how many IRQs you are currently consuming, run the command grep Dynamic-irq /proc/interrupts | wc -l.
  • In /etc/multipath.conf, setting max_fds to unlimited will prevent the multipathd daemon from starting up properly. As such, you should use a sufficiently high value instead for this setting.
  • When provisioning guests during installation, the RHN tools for guests option will not be available. When this occurs, the system will require an additional entitlement, separate from the entitlement used by dom0.
    To prevent the consumption of additional entitlements for guests, install the rhn-virtualization-common package manually before attempting to register the system to Red Hat Network.
  • virt-manager should not be left running continuously, as its memory use will grow over time. This could cause memory starvation.
    As such, you should only use virt-manager when needed. When extended use is required, it is advisable to periodically exit and restart virt-manager.
  • Network driver r8169 updated to add support for the following devices:
    • RTL8169sb/8110sb
    • RTL8169sc/8110sc
    • RTL8168b/8111b
    • RTL8101e
    • RTL8100e
  • The crash utility cannot be used to analyze kdump-generated x86_64 vmcores using the xen-syms-[release] binary of the Red Hat Enterprise Linux 5.2 kernel. To read these types of vmcores, use the command crash --xen_phys_start [address] /boot/xen-syms-[version] vmcore instead.
    To determine the value of [address], run the command cat /proc/iomem | grep Hypervisor. Something similar to the following output should appear:
    3ee00000-3fdfffff : Hypervisor code and data
    
    The [address] is the first number in the stated range; in this case, it is 3ee00000.
  • When installing Red Hat Enterprise Linux 5 on a guest, the guest is configured to explicitly use a temporary installation kernel provided by dom0. Once installation finishes, it can then use its own bootloader. However, this can only be achieved by forcing the guest's first reboot to be a shutdown.
    As such, when the Reboot button appears at the end of the guest installation, clicking it shuts down the guest, but does not reboot it. This is an expected behavior.
    Note that when you boot the guest after this it will then use its own bootloader.
  • Running rpmbuild on the compiz source RPM will fail if any KDE or qt development packages (for example, qt-devel) are installed. This is caused by a bug in the compiz configuration script.
    To work around this, remove any KDE or qt development packages before attempting to build the compiz package from its source RPM.
  • If your system has either ATI Radeon R500 or R600 graphics card equipped, firstboot will not run after installation. The system will go directly to the graphical login screen and skip firstboot altogether. If you attempt to run firstboot manually (i.e. from a failsafe terminal), the X session will crash.
    This issue is caused by the driver used by the ATI Radeon R500/R600 hardware. The default driver used by these graphics cards are still in technology preview. To work around this, backup your /etc/X11/xorg.conf file; then, configure X to use the supported vesa driver instead using the following command:
    system-config-display --reconfig --set-driver=vesa
    You can now run firstboot. To switch back to your old settings, restore your original /etc/X11/xorg.conf.
  • nfsroot is fully supported in this update. This allows users to run Red Hat Enterprise Linux 5.2 with its root file system (/) mounted via NFS.
    nfsroot was originally introduced in Red Hat Enterprise Linux 5 as a subset of the Technology Preview feature Stateless Linux. The full implementation of Stateless Linux remains a Technology Preview.
    At present, nfsroot has the following restrictions:
    • Writable directories that hold system files (for example, /tmp, /var, and /etc) must be replicated for each client and mounted independently with no sharing between clients. To do so, perform the following steps:
      1. Configure the client's root file system to boot in read-only mode. To do so, set READONLY to yes in /etc/sysconfig/readonly-root.
      2. Run cat /etc/rwtab to view a default list of directories and files mounted by each client in the format [type] [path].
        [type] can be either empty (an empty path), dirs (a directory tree that is copied, but is empty), or files (a file or directory tree copied intact).
      3. If any other files or directories need to writable but are not in /etc/rwtab, list them in the same format (i.e. [type] [path]) in a file under /etc/rwtab.d/. You may use any filename for this file.
    • SWAP is not supported over NFS.
    • SELinux cannot be enabled on nfsroot clients. In general, Red Hat does not recommend disabling SELinux. As such, customers must carefully consider the security implications of this action.
  • Installing Red Hat Enterprise Linux 5.2 on a system with multiple network interfaces and manually specified IPv6 addresses may result in a partially incorrect networking setup. When this occurs, your IPv6 settings will not be visible on the installed system.
    To work around this, set NETWORKING_IPV6 to yes in /etc/sysconfig/network. Then, restart your network connection using the command service network restart.
  • If your system uses the TSC timer, the gettimeofday system call may move backwards. This is because of an overflow issue that causes the TSC timer to jump forward significantly in some cases; when this occurs, the TSC timer will correct itself, but will ultimately register a movement backwards in time.
    This issue is particularly critical for time-sensitive systems, such as those used for transaction systems and databases. As such, if your system needs precision timing, Red Hat strongly recommends that you set the kernel to use another timer (for example, HPET).
  • The READ_AHEAD setting in the cciss driver is now removed. The cciss driver will now use the block layer default of 256. Testing has shown that the setting READ_AHEAD=1024 did not result in a consistent improvement in performance; in some situations, this setting could also cause the system to hang.
  • When multiple NFSv4 clients are repeatedly competing for read/write access to the same file on the NFS server, it is possible for one or more of those clients to stall for an indefinite period of time waiting for access. This occurs because the standard delay observed when failing to get an access delegation from the server is long enough for the client who currently owns such delegation to return it to the server and claim it back again.
  • If your system has yum-rhn-plugin-0.5.2-5.el5_1.2 (or an earlier version) installed, you will be unable to upgrade to Red Hat Enterprise Linux 5.2 through yum update. To work around this, upgrade your yum-rhn-plugin to the latest version (using yum update yum-rhn-plugin) before running yum update.
  • If your system has an older version of the gfs2-kmod package installed but the yum-kmod package is not installed, upgrading from Red Hat Enterprise Linux 5.1 to 5.2 will fail. To prevent this, install the latest version of yum-kmod first (using yum install yum-kmod) before running yum update.
  • Thanks to the help of upstream developers and testing customers, the FS-Cache feature has undergone significant changes in line with upstream FS-Cache implementation. Consequently, the technology preview implementation of FS-Cache in this release is now rendered obsolete.
    As such, Red Hat does not recommend the usage of FS-Cache. Note that FS-Cache will also be likely disabled for the next minor releases.
    Red Hat will be focusing on further refining this feature as per upstream specifications. Once an acceptable level of invasiveness and compatibility is reached, FS-Cache will then be re-introduced in Red Hat Enterprise Linux.
  • Anaconda cannot access more than 8 SmartArray controllers. If your system has more than 8 such controllers equipped, you will only be able to use storage on the first 8 controllers detected. Anaconda will fail when it attempts to open all other controllers (i.e. the 9th controller and above).
    Note, however, that these devices will still function properly after installation.
  • Firefox is now updated to version 3.0. This update features several fixes and enhancements, most notably:
    • Set homepages are now loaded correctly when the Firefox browser window is opened.
    • Firefox no longer crashes when you search for the string "do".
    • Firefox in 64-bit mode now loads the ext JavaScript library correctly. In previous versions of Firefox, web-based applications that used this library either took too long to load, or were never loaded at all.
    • A cross-site scripting flaw was discovered in the way Firefox handled the jar:URI scheme. This flaw made it possible for a malicious web site to conduct a scripting attack against the user. This security issue is now fixed in this update.
    • Several flaws were discovered in the way Firefox processed certain malformed content. Web sites that contained such content could cause Firefox to crash or even execute arbitrary code as the user running Firefox. This security issue is now fixed in this update.
    • A race condition was discovered in the way Firefox set the window.location property on a web page. With this flaw, it was possible for a web page to set an arbitrary Referer header; this could lead to a cross-site request forgery (CSRF) attack against websites that rely only on the Referer header. This security issue is now fixed in this update.
    • Firefox now renders correctly on laptops equipped with external display.
    Note, however, that this update of Firefox is not fully backwards compatible with all JavaScripts or Firefox plugins used today.
    Also, Red Hat has observed that several large commercial web applications have relied on the presence of some cross-site scripting flaws addressed by this Firefox update. These scripting flaws are described in the following links:
    Consequently, the use of these commercial web applications may result in some loss of functionality. You can observe this in the presence of additional JavaScript errors in the Firefox Error Console (Tools => Error Console). Red Hat is currently working with the corresponding vendors to address this.
  • The updated ixgbe driver does not support the Intel 82598AT (Copper Pond 10GbE).
  • Red Hat closely tracks the upstream Open Fabrics Enterprise Distribution (OFED) code base in order to provide a maximal level of enablement for this still evolving technology. As a consequence, Red Hat can only preserve API/ABI compatibility across minor releases to the degree that the upstream project does. This is an exception from the general practice in the development of Red Hat Enterprise Linux.
    Because of this, applications build on top of the OFED stack (listed below), might require recompilation or even source-level code changes when moving from one minor release of Red Hat Enterprise Linux to a newer one.
    This generally is not required for other applications, built on the Red Hat Enterprise Linux software stack.
    The components affected are:
    • dapl
    • compat-dapl
    • ibsim
    • ibutils
    • infiniband-diags
    • libcxgb3
    • libehca
    • libibcm
    • libibcommon
    • libibmad
    • libibumad
    • libibverbs
    • libipathverbs
    • libmlx4
    • libmthca
    • libnes
    • librmdacm
    • libsdp
    • mpi-selector
    • mpitests
    • mstflint
    • mvapich
    • mvapich2
    • ofed-docs
    • openib
    • openib-mstflint
    • openib-perftest
    • openib-tvflash
    • openmpi
    • opensm
    • perftest
    • qlvnictools
    • qperf
    • rds-tools
    • (future)
    • srptools
    • tvflash

1.2. x86 Architectures

  • Recording needs to be manually enabled on Dell M4300 and M6300. To do this, perform the following steps:
    1. Open alsamixer.
    2. Press Tab to toggle [Capture] in the View field (located at the upper left part of the menu).
    3. Press the Space bar.
    4. To verify that recording is enabled, the text above the ADCMux field should display L R CAPTUR.

1.3. x86-64 Architectures

  • Recording needs to be manually enabled on Dell M4300 and M6300. To do this, perform the following steps:
    1. Open alsamixer.
    2. Press Tab to toggle [Capture] in the View field (located at the upper left part of the menu).
    3. Press the Space bar.
    4. To verify that recording is enabled, the text above the ADCMux field should display L R CAPTUR.
  • On an IBM T61 laptop, Red Hat recommends that you refrain from clicking the glxgears window (when glxgears is run). Doing so can lock the system.
    To prevent this from occurring, disable the tiling feature. To do so, add the following line in the Device section of /etc/X11/xorg.conf:
    Option "Tiling" "0"
    
  • The distribution version of the release notes stated that crash dumping through kexec and kdump did not function reliably with HP Smart Array controllers. As of general availability, this issue is now resolved.

1.4. PowerPC Architectures

  • Recording needs to be manually enabled on Dell M4300 and M6300. To do this, perform the following steps:
    1. Open alsamixer.
    2. Press Tab to toggle [Capture] in the View field (located at the upper left part of the menu).
    3. Press the Space bar.
    4. To verify that recording is enabled, the text above the ADCMux field should display L R CAPTUR.
  • The setroubleshootd daemon no longer exits with a fault the first time sealert attempts to connect to the daemon.

1.5. ia64 Architecture

  • Recording needs to be manually enabled on Dell M4300 and M6300. To do this, perform the following steps:
    1. Open alsamixer.
    2. Press Tab to toggle [Capture] in the View field (located at the upper left part of the menu).
    3. Press the Space bar.
    4. To verify that recording is enabled, the text above the ADCMux field should display L R CAPTUR.
  • Running perftest will fail if different CPU speeds are detected. As such, you should disable CPU speed scaling before running perftest.
  • When the kdump kernel is booted, the following error will appear in the boot log:
    mknod: /tmp/initrd.[numbers]/dev/efirtc: No such file or directory
    
    This error results from a malformed request to create the efirtc in an incorrect path. However, the device path in question is also created statically in the initramfs when the kdump service is started. As such, the run-time creation of the device node is redundant, harmless, and should not affect the performance of kdump.
  • The distribution version of the release notes stated that crash dumping through kexec and kdump did not function reliably with HP Smart Array controllers. As of general availability, this issue is now resolved.
  • Some systems may be unable to boot the kdump kernel properly. In such cases, use the machvec=dig kernel parameter.