- Intel Xeon E5-XXXX V2 Series Processor running on the C600 chipset is not supported in Red Hat Enterprise Linux 6.3. An "unsupported hardware" message can therefore be reported by the kernel.
- The Red Hat Enterprise Linux 6.3 kernels upgraded the
mlx4modules to a later version. If the modules are used together with, for example, the HP InfiniBand Enablement Kit, the behavior is different. Consequently, certain Mellanox cards do not come up with network interfaces on Red Hat Enterprise Linux 6.3. To work around this problem, the
mlx7_coremodule has to be loaded with the
port_type_arrayoption and a
2parameter for each used InfiniBand card. Follow this example to manually load the driver for two cards in the system:
modprobe mlx4_core port_type_array=2,2~]#
ip aThe last of the above commands will show the new interfaces. To configure these parameters to be applied by the system when the modules are loaded, run:
echo 'options mlx4_core port_type_array=2,2' >/etc/modprobe.d/mlx4_core.conf
- When using Chelsio's iSCSI HBAs for an iSCSI root partition, the first boot after install fails. This occurs because Chelsio's iSCSI HBA is not properly detected. To work around this issue, users must add the
iscsi_firmwareparameter to grub's kernel command line. This will signal to dracut to boot from the iSCSI HBA.
- In Red Hat Enterprise Linux 6.3, three module parameters (
rss_xor) that were supported by older versions of the
mlx4_endriver have become obsolete and are no longer used. If you supply these parameters, the Red Hat Enterprise Linux 6.3 driver will ignore them and log a warning.
- Due to a race condition, in certain cases, writes to RAID4/5/6 while the array is reconstructing could hang the system.
- The installation of Red Hat Enterprise Linux 6.3 i386 may occasionally fail. To work around this issue, add the following parameter to the kernel command line:
- If a device reports an error, while it is opened (via the
open(2)system call), then the device is closed (via the
close(2)system call), and the
/dev/disk/by-idlink for the device may be removed. When the problem on the device that caused the error is resolved, the
by-idlink is not re-created. To work around this issue, run the following command:
echo 'change' > /sys/class/block/sdX/uevent
- Platforms with BIOS/UEFI that are unaware of PCI-e SR-IOV capabilities may fail to enable virtual functions
- When an HBA that uses the
mpt2sasdriver is connected to a storage using an SAS switch LSI SAS 6160, the driver may become unresponsive during Controller Fail Drive Fail (CFDF) testing. This is due to faulty firmware that is present on the switch. To fix this issue, use a newer version (14.00.00.00 or later) of firmware for the LSI SAS 6160 switch.
- If appropriate SCSI device handlers (
scsi_dhmodules) are not available when the storage driver (for example,
lpfc) is first loaded, I/O operations may be issued to SCSI multipath devices that are not ready for those I/O operations. This can result in significant delays during system boot and excessive I/O error messages in the kernel log.Provided the storage driver is loaded before
multipathdis started (which is the default behavior), users can work around this issue by making sure the appropriate SCSI device handlers (
scsi_dhmodules) are available by specifying one of the following kernel command line parameters which dracut consumes:
Note that the order of the listed
scsi_dhmodules does not matter.Specifying one of the above parameters causes the
scsi_dhmodule(s) to load before the storage driver is loaded or multipath is started.
- In some cases, Red Hat Enterprise Linux 6 guests running fully-virtualized under Red Hat Enterprise Linux 5 experience a time drift or fail to boot. In other cases, drifting may start after migration of the virtual machine to a host with different speed. This is due to limitations in the Red Hat Enterprise Linux 5 Xen hypervisor. To work around this, add the
nohpetparameter or, alternatively, the
clocksource=jiffiesparameter to the kernel command line of the guest. Or, if running under Red Hat Enterprise Linux 5.7 or newer, locate the guest configuration file for the guest and add the
hpet=0parameter in it.
- On some systems, Xen full-virt guests may print the following message when booting:
WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing <number>MB of RAMIt is possible to avoid the memory trimming by using the
disable_mtrr_trimkernel command line option.
perf recordcommand becomes unresponsive when specifying a tracepoint event and a hardware event at the same time.
- On 64-bit PowerPC, the following command may cause kernel panic:
./perf record -agT -e sched:sched_switch -F 100 -- sleep 3
- Applications are increasingly using more than 1024 file descriptors. It is not recommended to increase the default soft limit of file descriptors because it may break applications that use the
select()call. However, it is safe to increase the default hard limit; that way, applications requiring a large amount of file descriptors can increase their soft limit without needing root privileges and without any user intervention.
- In Red Hat Enterprise Linux 6.2 and Red Hat Enterprise Linux 6.3, the default value for
sysctl vm.zone_reclaim_modeis now
0, whereas in Red Hat Enterprise Linux 6.1 it was
- Using Alsa with an HDA Intel sound card and the Conexant CX20585 codec causes sound and recording failures. To work around this issue, add the following line to the
options snd-hda-intel model=thinkpad
- 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 continuous messages on the host console:
bfa xxxx:xx:xx.x: Base port (WWN = xx:xx:xx:xx:xx:xx:xx:xx) lost fabric connectivityTo work around this issue, unload the Brocade
lpfcdriver is deprecating the
mboxinterface as it is no longer used by the Emulex tools. Reads and writes are now stubbed out and only return the
-EPERM(Operation not permitted) symbol.
- In Red Hat Enterprise Linux 6, a legacy bug in the PowerEdge Expandable RAID Controller 5 (PERC5) which causes the kdump kernel to fail to scan for
scsidevices. It is usually triggered when a large amounts of I/O operations are pending on the controller in the first kernel before performing a kdump.
- In Red Hat Enterprise Linux 6.2 and later, due to security concerns, addresses in
/proc/modulesshow all zeros when accessed by a non-root user.
- Superfluous information is displayed on the console due to a correctable machine check error occurring. This information can be safely ignored by the user. Machine check error reporting can be disabled by using the
nomcekernel boot option, which disables machine check error reporting, or the
mce=ignore_cekernel boot option, which disables correctable machine check error reporting.
- The order in which PCI devices are scanned may change from one major Red Hat Enterprise Linux release to another. This may result in device names changing, for example, when upgrading from Red Hat Enterprise Linux 5 to 6. You must confirm that a device you refer to during installation, is the intended device.One way to assure the correctness of device names is to, in some configurations, determine the mapping from the controller name to the controller's PCI address in the older release, and then compare this to the mapping in the newer release, to ensure that the device name is as expected.The following is an example from /var/log/messages:
kernel: cciss0: <0x3230> at PCI 0000:1f:00.0 IRQ 71 using DAC … kernel: cciss1: <0x3230> at PCI 0000:02:00.0 IRQ 75 using DACIf the device name is incorrect, add the
pci=bfsortparameter to the kernel command line, and check again.
- Enabling CHAP (Challenge-Handshake Authentication Protocol) on an iSCSI target for the
be2iscsidriver results in kernel panic. To work around this issue, disable CHAP on the iSCSI target.
- Newer VPD (Vital Product Data) blocks can exceed the size the
tg3driver normally handles. As a result, some of the routines that operate on the VPD blocks may fail. For example, the
nvramtest fails when running the
ethtool –tcommand on BCM5719 and BCM5720 Ethernet Controllers.
- Running the
ethtool -tcommand on BCM5720 Ethernet controllers causes a loopback test failure because the
tg3driver does not wait long enough for a link.
tg3driver in Red Hat Enterprise Linux 6.2 does not include support for Jumbo frames and TSO (TCP Segmentation Offloading) on BCM5719 Ethernet controllers. As a result, the following error message is returned when attempting to configure, for example, Jumbo frames:
SIOCSIFMTU: Invalid argument
- The default interrupt configuration for the Emulex LPFC FC/FCoE driver has changed from INT-X to MSI-X. This is reflected by the
lpfc_use_msimodule parameter (in
/sys/class/scsi_host/host#/lpfc_use_msi) being set to
2by default, instead of the previous
0.Two issues provide motivation for this change: SR-IOV capability only works with the MSI-X interrupt mode, and certain recent platforms only support MSI or MSI-X.However, the change to the LPFC default interrupt mode can bring out host problems where MSI/MSI-X support is not fully functional. Other host problems can exist when running in the INT-X mode.If any of the following symptoms occur after upgrading to, or installing Red Hat Enterprise Linux 6.2 with an Emulex LPFC adapter in the system, change the value of the
- The initialization or attachment of the
lpfcadapter may fail with mailbox errors. As a result, the
lpfcadapter is not configured on the system. The following message appear in
lpfc 0000:04:08.0: 0:0:0443 Adapter failed to set maximum DMA length mbxStatus x0 lpfc 0000:04:08.0: 0:0446 Adapter failed to init (255), mbxCmd x9 CFG_RING, mbxStatus x0, ring 0 lpfc 0000:04:08.0: 0:1477 Failed to set up hba ACPI: PCI interrupt for device 0000:04:08.0 disabled
- While the
lpfcadapter is operating, it may fail with mailbox errors, resulting in the inability to access certain devices. The following message appear in
lpfc 0000:0d:00.0: 0:0310 Mailbox command x5 timeout Data: x0 x700 xffff81039ddd0a00 lpfc 0000:0d:00.0: 0:0345 Resetting board due to mailbox timeout lpfc 0000:0d:00.0: 0:(0):2530 Mailbox command x23 cannot issue Data: xd00 x2
- Performing a warm reboot causes any subsequent boots to halt or stop because the BIOS is detecting the
lpfcadapter. The system BIOS logs the following messages:
Installing Emulex BIOS ...... Bringing the Link up, Please wait... Bringing the Link up, Please wait...
- The minimum firmware version for NIC adapters managed by
netxen_nicis 4.0.550. This includes the boot firmware which is flashed in option ROM on the adapter itself.
- High stress on 64-bit IBM POWER series machines prevents kdump from successfully capturing the
vmcore. As a result, the second kernel is not loaded, and the system becomes unresponsive.
- Triggering kdump to capture a
vmcorethrough the network using the Intel 82575EB ethernet device in a 32 bit environment causes the networking driver to not function properly in the kdump kernel, and prevent the
vmcorefrom being captured.
- Memory Type Range Register (MTRR) setup on some hyperthreaded machines may be incorrect following a suspend/resume cycle. This can cause graphics performance (specifically, scrolling) to slow considerably after a suspend/resume cycle.To work around this issue, disable and then re-enable the hyperthreaded sibling CPUs around suspend/resume, for example:
#!/bin/sh # Disable hyper-threading processor cores on suspend and hibernate, re-enable # on resume. # This file goes into /etc/pm/sleep.d/ case $1 in hibernate|suspend) echo 0 > /sys/devices/system/cpu/cpu1/online echo 0 > /sys/devices/system/cpu/cpu3/online ;; thaw|resume) echo 1 > /sys/devices/system/cpu/cpu1/online echo 1 > /sys/devices/system/cpu/cpu3/online ;; esac
- In Red Hat Enterprise Linux 6.2,
nmi_watchdogregisters with the
perfsubsystem. Consequently, during boot, the
perfsubsystem grabs control of the performance counter registers, blocking OProfile from working. To resolve this, either boot with the
nmi_watchdog=0kernel parameter set, or run the following command to disable it at run time:
echo 0 > /proc/sys/kernel/nmi_watchdogTo re-enable
nmi-watchdog, use the following command
echo 1 > /proc/sys/kernel/nmi_watchdog
- Due to the way ftrace works when modifying the code during start-up, the NMI watchdog causes too much noise and ftrace can not find a quiet period to instrument the code. Consequently, machines with more than 512 CPUs will encounter issues with the NMI watchdog. Such issues will return error messages similar to
BUG: NMI Watchdog detected LOCKUPand have either
ipi_handlerin the backtrace. To work around this issue, disable NMI watchdog by setting the
nmi_watchdog=0kernel parameter, or using the following command at run time:
echo 0 > /proc/sys/kernel/nmi_watchdog
- On 64-bit POWER systems the EHEA NIC driver will fail when attempting to dump a
vmcorevia NFS. To work around this issue, utilize other kdump facilities, for example dumping to the local file system, or dumping over SSH.
- A BIOS emulated floppy disk might cause the installation or kernel boot process to hang. To avoid this, disable emulated floppy disk support in the BIOS.
- The preferred method to enable nmi_watchdog on 32-bit x86 systems is to use either
nmi_watchdog=lapicparameters. The parameter
nmi_watchdog=1is not supported.
- The kernel parameter,
pci=noioapicquirk, is required when installing the 32-bit variant of Red Hat Enterprise Linux 6 on HP xw9300 workstations. Note that the parameter change is not required when installing the 64-bit variant.