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2.19. kernel
The kernel packages contain the Linux kernel, the core of any Linux operating system.
- On Microsoft Hyper-V, a Red Hat Enterprise Linux 5 guest can start with more memory than the host's NUMA node memory, which results in a kernel panic on the guest. To prevent the crash in this scenario, set the
numa=off
boot parameter on the kernel command line. - On Microsoft Windows Server 2012 containing large dynamic VHDX (Hyper-V virtual hard disk) files and using the ext3 file system, a call trace can appear, and, consequently, it is not possible to shut down the guest. To work around this problem, use the ext4 file system or set a logical block size of 1MB when creating a VHDX file. Note that this can only be done by using Microsoft PowerShell as the Hyper-V manager does not expose the
–BlockSizeBytes
option which has the default value of 32MB. To create a dynamix VHDX file with an approximate size of 2.5TB and 1MB block size run:New-VHD –Path .\MyDisk.vhdx –SizeBytes 5120MB –BlockSizeBytes 1MB -Dynamic
- The
sar
andsadf
commands can terminate unexpectedly with a segmentation fault when run on 64-bit PowerPC architecture. (BZ#BZ#984866) - Hardware support for Intel/QLogix QLE7300 series InfiniBand adapters, which was included in Red Hat Enterprise Linux 5.9, has been removed at Red Hat Enterprise Linux 5.10. Please refer to Red Hat Knowledge Solution 426383 for more information.
- Earlier versions of the Broadcom MFW firmware on bnx2x devices have known bugs. A specific link problem is known to affect BCM57810 based devices with 10GBASE-KR connections. Consequently, depending on the exact timing, the network interface can fail to establish the link. To establish a more reliable link, update the MFW firmware on the bnx2x device's EEPROM (Electrically Erasable Programmable Read-Only Memory) to version 7.4.19 or later. The current version can be checked running
ethtool -i $NET_DEVICE | grep firmware-version
. Please consult your hardware vendor or manufacturer for instructions on how to update the MFW firmware on bnx2x devices. - The Emulex
lpfc
driver is missing functionality required to support 16 Gb point-to-point configurations for all adapters in Red Hat Enterprise Linux 5. All other currently available 16 Gblpfc
configurations are supported on most adapters available. Specifically, the LPe16000B adapter is not supported for any configuration, and the LPe16000A adapter is supported for all configurations besides a point-to-point configuration. - Red Hat Enterprise Linux 5 can become unresponsive or even terminate due to the lack of ticketed spinlocks in the
shrink_active_list()
function. - When USB hardware uses the ACM interface, there is a race condition that can lead to a system deadlock due to the spinlocks not disabling interrupts. This has been noticed through various types of softlockups. To workaround this problem, reboot the machine.
- If kdump is configured on an i686 system using a non-PAE kernel and memory larger than 4 GB, it creates an elf core header which includes extra unavailable memory range. This causes kdump to become unresponsive.
- A large number of kernel log messages may flood
netconsole
while under heavy RX traffic, causing thenetconsole
kernel module to stop working. To work around this issue, avoid the use ofnetconsole
, or remove the netconsole module using thermmod netconsole
command and re-configure it again using theinsmod netconsole
command. - To update firmware on Mellanox cards, use mstflint which replaces the outdated tvflash utility.
- The kernel in Red Hat Enterprise Linux 5 does not support Data Center Bridging (DCB). Software-based Fibre Channel over Etherner (FCoE) is a Technology Preview and it is therefore recommended to use Red Hat Enterprise Linux 6 for fully supported software-based FCoE. The following hardware-accelerated FCoE cards are fully supported in Red Hat Enterprise Linux 5: Emulex LPFC, QLogic qla2xxx, Brocade BFA. (BZ#860112)
- The following problems can occur when using Brocade 1010 and 1020 Converged Network Adapters (CNAs):
- BIOS firmware may not be able to log in the Fibre Channel over Ethernet (FCoE) session when loading a Brocade optional BIOS, which causes the server to be unable to boot and the following error message to appear:
Adapter 1/0/0 Link initialization failed. Disabling BIOS
- Configuration cannot be saved via serial port of the server. Use a physical console or Brocade HSM software.
Contact Brocade for additional information on these problems. - In network only, use of Brocade Converged Network Adapters (CNAs) switches that are not properly configured to work with Brocade FCoE functionality can cause a continuous linkup/linkdown condition. This causes error messages to continuously appear on the host console:
bfa xxxx:xx:xx.x: Base port (WWN = xx:xx:xx:xx:xx:xx:xx:xx) lost fabric connectivity
To work around this problem, unload the Brocade BFA driver. - Master Boot Record (MBR) or the /boot partition can be installed on an incorrect disk if the server boots from storage area network (SAN) with many Logical Unit Numbers (LUNs) assigned. To work around this problem, partition the space manually so that the operating system uses only the boot LUN as the root (/) and /boot partitions. (BZ#852305)
- Qemu-kvm does not check if a given CPU flag is really supported by the KVM kernel module. Attempting to enable the "acpi" flag can lead to a kernel panic on guest machines. To work around this problem, do not enable the "acpi" CPU flag in the configuration of a virtual machine. (BZ#838921)
- Running the
ethtool --identify
command in a production environment blocks network traffic and certain network configuration operations until ethtool is aborted. To prevent this problem, do not runethtool --identify
in a production environment; this command is supposed for debugging purposes only. - Starting with Red Hat Enterprise Linux 5.8, the size of I/O operations allowed by the NFS server has been increased by default. The new default max block size varies depending on RAM size, with a maximum of 1M (1048576 bytes).This may cause problems for 32-bit servers configured to use large numbers of
nfsd
threads. For such servers, we recommend decreasing the number of threads, or decreasing the I/O size by writing to the/proc/fs/nfsd/max_block_size
file before startingnfsd
. For example, the following command restores the previous defaultiosize
of 32k:~]#
echo 32767 >/proc/fs/nfsd/max_block_size
(BZ#765751 ) - If the
qla4xxx
driver fails to discover all iSCSI targets, make sure toClear Persistent Targets
and set up iSCSI again via CTRL+Q in the Qlogic iSCSI option ROM BIOS. - The OProfile infrastructure in Red Hat Enterprise Linux 5 does not support the hardware performance counters of the AMD family 0x15 processor family; profiling is only available in timer interrupt mode. When profiling on bare metal, OProfile automatically selects the timer interrupt mode. When running under kernel-xen, due to different CPU family reporting, OProfile must be explicitly configured to use timer interrupt mode. This is possible by adding
options oprofile timer=1
to the/etc/modprobe.conf
file. (BZ#720587) - Red Hat Enterprise Linux 5 may become unresponsive due to the lack of ticketed spinlocks in the
shrink_active_list()
function. As a result, thespin_lock_irq(&zone->lru_lock)
operation disables interrupts, and the following error message is returned when the system hangs:NMI Watchdog detected LOCKUP
- Booting a Red Hat Enterprise Linux 5 system with a connected DVD drive and the
smartd
service running hangs with the following error messages:Starting smartd: hdc: drive_cmd: status=0x58 { DriveReady SeekComplete DataRequest } ide: failed opcode was: 0xa1 hdc: status error: status=0x58 { DriveReady SeekComplete DataRequest } ide: failed opcode was: unknown hdc: drive not ready for command hdc: status timeout: status=0xd8 { Busy } ide: failed opcode was: unknown hdc: drive not ready for command hdc: ATAPI reset complete hdc: status error: status=0x58 { DriveReady SeekComplete DataRequest } ⋮
To work around this issue, disconnect the DVD drive or turn thesmartd
service off with the following command:~]#
chkconfig smartd off
- The
modify SRQ
verb is not supported by theeHCA
adapter and will fail with an error code when called from an application context. - In RHEL 5.8, machine check (MCE) support for Intel Nehalem or newer CPUs (family 6, model >= 26) is disabled. This is a change from RHEL5.6 and earlier where basic MCE support was provided for these CPUs. Uncorrected CPU and memory errors will cause an immediate CPU shut down and system panic.
- On a Red Hat Enterprise Linux 5.8 system and later, while hand-loading the i386 (32-bit) kernel on z210/z210 SFF with BIOS 1.08, the system may fail to boot. To workaround this issue, please add the following parameter to the boot command line option:
pci=nosort
(BZ#703538) - Red Hat Enterprise Linux 5.7 has introduced a new multicast snooping feature for the bridge driver used for virtualization (virt-bridge). This feature is disabled by default in order to not break any existing configurations. To enable this feature, please set the following tunnable parameter to
1
:/sys/class/net/breth0/bridge/multicast_snooping
Please note that when multicast snooping is enabled, it may cause a regression with certain switches where it causes a break in the multicast forwarding for some peers. - By default, libsas defines a wideport based on the attached SAS address, rather than the specification compliant “strict” definition of also considering the local SAS address. In Red Hat Enterprise Linux 5.8 and later, only the default “loose” definition is available. The implication is that if an OEM configures an SCU controller to advertise different SAS addresses per PHY, but hooks up a wide target or an expander to those PHYs, libsas will only create one port. The expectation, in the “strict” case, is that this would result in a single controller multipath configuration.It is not possible to use a single controller multipath without the
strict_wide_port
functionality. Multi-controller multipath should behave as a expected.A x8 multipath configuration through a single expander can still be obtained under the following conditions:- Start with an SCU SKU that exposes (2) x4 controllers (total of 8 PHYs)
- Assign
sas_address1
to all the PHYs oncontroller1
- Assign
sas_address2
to all the PHYs oncontroller2
- Hook up the expander across all 8 PHYs
- Configure multipath across the two controller instances
It is critical forcontroller1
to have a distinct address fromcontroller2
, otherwise the expander will be unable to correctly route connection requests to the proper initiator. (BZ#651837) - On a Red Hat Enterprise Linux 5 system, it is advisable to update the firmware of the HP ProLiant Generation 6 (G6) controller's firmware to version 5.02 or later. Once the firmware is successfully updated, reboot the system and Kdump will work as expected.HP G6 controllers include: P410i, P411, P212, P712, and P812In addition, kdump may fail when using the HP Smart Array 5i Controller on a Red Hat Enterprise Linux 5 system. (BZ#695493)
- On Red Hat Enterprise Linux 5.5 and later, suspending the system with the
lpfc
driver loaded may crash the system during the resume operation. Therefore, systems using thelpfc
driver, either unload thelpfc
driver before the system is suspended, or ,if that is not possible, do not suspend the system. (BZ#703631) - NUMA class systems should not be booted with a single memory node configuration. Configuration of single node NUMA systems will result in contention for the memory resources on all of the non-local memory nodes. As only one node will have local memory the CPUs on that single node will starve the remaining CPUs for memory allocations, locks, and any kernel data structure access. This contention will lead to the "CPU#n stuck for 10s!" error messages. This configuration can also result in NMI watchdog timeout panics if a spinlock is acquired via
spinlock_irq()
and held for more than 60 seconds. The system can also hang for indeterminate lengths of time.To minimize this problem, NUMA class systems need to have their memory evenly distributed between nodes. NUMA information can be obtained from dmesg output as well as from thenumastat
command. (BZ#529428) - When upgrading from Red Hat Enterprise Linux 5.0, 5.1 or 5.2 to more recent releases, the gfs2-kmod may still be installed on the system. This package must be manually removed or it will override the (newer) version of GFS2 which is built into the kernel. Do not install the
gfs2-kmod
package on later versions of Red Hat Enterprise Linux.gfs2-kmod
is not required since GFS2 is built into the kernel from 5.3 onwards. The content of the gfs2-kmod package is considered a Technology Preview of GFS2, and has not received any updates since Red Hat Enterprise Linux 5.3 was released.Note that this note only applies to GFS2 and not to GFS, for which the gfs-kmod package continues to be the only method of obtaining the required kernel module. - Issues might be encountered on a system with 8Gb/s LPe1200x HBAs and firmware version 2.00a3 when the Red Hat Enterprise Linux 5.8 kernel is used with the in-box LPFC driver. Such issues include loss of LUNs and/or fiber channel host hangs during fabric faults with multipathing.To work around these issues, it is recommended to either:
- Downgrade the firmware revision of the 8Gb/s LPe1200x HBA to revision 1.11a5, or
- Modify the LPFC driver’s
lpfc_enable_npiv
module parameter to zero.When loading the LPFC driver from the initrd image (i.e. at system boot time), add the lineoptions lpfc_enable_npiv=0
to/etc/modprobe.conf
and re-build the initrd image.When loading the LPFC driver dynamically, include thelpfc_enable_npiv=0
option in the insmod or modprobe command line.
For additional information on how to set the LPFC driver module parameters, refer to the Emulex Drivers for Linux User Manual. - If AMD IOMMU is enabled in BIOS on ProLiant DL165 G7 systems, the system will reboot automatically when IOMMU attempts to initialize. To work around this issue, either disable IOMMU, or update the BIOS to version
2010.09.06
or later. (BZ#628534) - As of Red Hat Enterprise Linux 5.6, the
ext4
file system is fully supported. However, provisioning ext4 file systems with the anaconda installer is not supported, and ext4 file systems need to be provisioned manually after the installation. (BZ#563943) - In some cases the NFS server fails to notify NFSv4 clients about renames and unlinks done by other clients, or by non-NFS users of the server. An application on a client may then be able to open the file at its old pathname (and read old cached data from it, and perform read locks on it), long after the file no longer exists at that pathname on the server.To work around this issue, use NFSv3 instead of NFSv4. Alternatively, turn off support for leases by writing
0
to/proc/sys/fs/leases-enable
(ideally on boot, before the nfs server is started). This change prevents NFSv4 delegations from being given out, restore correctness at the expense of some performance. - Some laptops may generate continuous events in response to the lid being shut. Consequently, the gnome-power-manager utility will consume CPU resources as it responds to each event. (BZ#660644)
- A kernel panic may be triggered by the lpfc driver when multiple Emulex OneConnect Universal Converged Network Adapter initiators are included in the same Storage Area Network (SAN) zone. Typically, this kernel panic will present after a cable is pulled or one of the systems is rebooted. To work around this issue, configure the SAN to use single initiator zoning. (BZ#574858)
- If a Huawei USB modem is unplugged from a system, the device may not be detected when it is attached again. To work around this issue, the usbserial and usb-storage driver modules need to be reloaded, allowing the system to detect the device. Alternatively, the if the system is rebooted, the modem will be detected also. (BZ#517454)
- Memory on-line is not currently supported with the Boxboro-EX platform. (BZ#515299)
- Unloading a PF (SR-IOV Physical function) driver from a host when a guest is using a VF (virtual function) from that device can cause a host crash. A PF driver for an SR-IOV device should not be unloaded until after all guest virtual machines with assigned VFs from that SR-IOV device have terminated. (BZ#514360)
- Data corruption on NFS file systems might be encountered on network adapters without support for error-correcting code (ECC) memory that also have TCP segmentation offloading (TSO) enabled in the driver. Note: data that might be corrupted by the sender still passes the checksum performed by the IP stack of the receiving machine A possible work around to this issue is to disable TSO on network adapters that do not support ECC memory. (BZ#504811)
- After installation, a System z machine with a large number of memory and CPUs (e.g. 16 CPU's and 200GB of memory) might may fail to IPL. To work around this issue, change the line
ramdisk=/boot/initrd-2.6.18-<kernel-version-number>.el5.img
toramdisk=/boot/initrd-2.6.18-<kernel-version-number>.el5.img,0x02000000
The commandzipl -V
should now show0x02000000
as the starting address for the initial RAM disk (initrd). Stop the logical partition (LPAR), and then manually increase the storage size of the LPAR. - On certain hardware configurations the kernel may panic when the Broadcom iSCSI offload driver (
bnx2i.ko
andcnic.ko
) is loaded. To work around this do not manually load the bnx2i or cnic modules, and temporarily disable theiscsi
service from starting. To disable the iscsi service, run:~]#
chkconfig --del iscsi
~]#chkconfig --del iscsid
On the first boot of your system, theiscsi
service may start automatically. To bypass this, during bootup, enter interactive start up and stop the iscsi service from starting. - In Red Hat Enterprise Linux 5, invoking the kernel system call "setpriority()" with a "which" parameter of type "PRIO_PROCESS" does not set the priority of child threads. (BZ#472251)
- A change to the cciss driver in Red Hat Enterprise Linux 5.4 made it incompatible with the
echo disk < /sys/power/state
suspend-to-disk operation. Consequently, the system will not suspend properly, returning messages such as:Stopping tasks: ====================================================================== stopping tasks timed out after 20 seconds (1 tasks remaining): cciss_scan00 Restarting tasks...<6> Strange, cciss_scan00 not stopped done
(BZ#513472) - The kernel is unable to properly detect whether there is media present in a CD-ROM drive during kickstart installs. The function to check the presence of media incorrectly interprets the "logical unit is becoming ready" sense, returning that the drive is ready when it is not. To work around this issue, wait several seconds between inserting a CD and asking the installer (anaconda) to refresh the CD. (BZ#510632)
- When a cciss device is under high I/O load, the kdump kernel may panic and the vmcore dump may not be saved successfully. (BZ#509790)
- Configuring IRQ SMP affinity has no effect on some devices that use message signaled interrupts (MSI) with no MSI per-vector masking capability. Examples of such devices include Broadcom NetXtreme Ethernet devices that use the
bnx2
driver.If you need to configure IRQ affinity for such a device, disable MSI by creating a file in/etc/modprobe.d/
containing the following line:options bnx2 disable_msi=1
Alternatively, you can disable MSI completely using the kernel boot parameterpci=nomsi
. (BZ#432451) - The
smartctl
tool cannot properly read SMART parameters from SATA devices. (BZ#429606) - IBM T60 laptops will power off completely when suspended and plugged into a docking station. To avoid this, boot the system with the argument
acpi_sleep=s3_bios
. (BZ#439006) - The QLogic iSCSI Expansion Card for the IBM Bladecenter provides both ethernet and iSCSI functions. Some parts on the card are shared by both functions. However, the current
qla3xxx
andqla4xxx
drivers support ethernet and iSCSI functions individually. Both drivers do not support the use of ethernet and iSCSI functions simultaneously.Because of this limitation, successive resets (via consecutiveifdown
/ifup
commands) may hang the device. To avoid this, allow a 10-second interval after anifup
before issuing anifdown
. Also, allow the same 10-second interval after anifdown
before issuing anifup
. This interval allows ample time to stabilize and re-initialize all functions when anifup
is issued. (BZ#276891) - Laptops equipped with the Cisco Aironet MPI-350 wireless may hang trying to get a DHCP address during any network-based installation using the wired ethernet port.To work around this, use local media for your installation. Alternatively, you can disable the wireless card in the laptop BIOS prior to installation (you can re-enable the wireless card after completing the installation). (BZ#213262)
- Hardware testing for the Mellanox MT25204 has revealed that an internal error occurs under certain high-load conditions. When the
ib_mthca
driver reports a catastrophic error on this hardware, it is usually related to an insufficient completion queue depth relative to the number of outstanding work requests generated by the user application.Although the driver will reset the hardware and recover from such an event, all existing connections at the time of the error will be lost. This generally results in a segmentation fault in the user application. Further, ifopensm
is running at the time the error occurs, then you need to manually restart it in order to resume proper operation. (BZ#251934) - The IBM T41 laptop model does not enter properly; as such, will still consume battery life as normal. This is because Red Hat Enterprise Linux 5 does not yet include the
radeonfb
module.To work around this, add a script namedhal-system-power-suspend
to/usr/share/hal/scripts/
containing the following lines:chvt 1 radeontool light off radeontool dac off
This script will ensure that the IBM T41 laptop enters properly. To ensure that the system resumes normal operations properly, add the scriptrestore-after-standby
to the same directory as well, containing the following lines:radeontool dac on radeontool light on chvt 7
(BZ#227496) - If the
edac
module is loaded, BIOS memory reporting will not work. This is because theedac
module clears the register that the BIOS uses for reporting memory errors.The current Red Hat Enterprise Linux Driver Update Model instructs the kernel to load all available modules (including theedac
module) by default. If you wish to ensure BIOS memory reporting on your system, you need to manually blacklist theedac
modules. To do so, add the following lines to/etc/modprobe.conf
:blacklist edac_mc blacklist i5000_edac blacklist i3000_edac blacklist e752x_edac
(BZ#441329) - Due to outstanding driver issues with hardware encryption acceleration, users of Intel WiFi Link 4965, 5100, 5150, 5300, and 5350 wireless cards are advised to disable hardware accelerated encryption using module parameters. Failure to do so may result in the inability to connect to Wired Equivalent Privacy (WEP) protected wireless networks after connecting to WiFi Protected Access (WPA) protected wireless networks.To do so, add the following options to
/etc/modprobe.conf
:alias wlan0 iwlagn options iwlagn swcrypto50=1 swcrypto=1
where wlan0 is the default interface name of the first Intel WiFi Link device.(BZ#468967) - A kernel security fix released between Red Hat Enterprise Linux 5.7 and 5.8 may prevent PCI passthrough working and guests starting. Refer to Red Hat Knowledgebase article 66747 for further details.
The following note applies to the PowerPC architecture:
- The size of the PowerPC kernel image is too large for OpenFirmware to support. Consequently, network booting will fail, resulting in the following error message:
Please wait, loading kernel... /pci@8000000f8000000/ide@4,1/disk@0:2,vmlinux-anaconda: No such file or directory boot:
To work around this:- Boot to the OpenFirmware prompt, by pressing the '8' key when the IBM splash screen is displayed.
- Run the following command:
~]#
setenv real-base 2000000
- Boot into System Management Services (SMS) with the command:
~]#
0> dev /packages/gui obe
(BZ#462663)