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issue, users must add the iscsi_firmware parameter to grub's kernel command line.
This will signal to dracut to boot from the iSCSI HBA.
kernel component
The installation of Red Hat Enterprise Linux 6.3 i386 and later may occasionally fail. To
work around this issue, add the following parameter to the kernel command line:
vmalloc=256MB
kernel component
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-id link for the device
may be removed. When the problem on the device that caused the error is resolved, the by-
id link is not re-created. To work around this issue, run the following command:
~]# echo 'change' > /sys/class/block/sdX/uevent
kernel component
When an HBA that uses the mpt2sas driver 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.
kernel component, BZ#74 5713
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 nohpet
parameter or, alternatively, the clocksource=jiffies parameter 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=0 parameter in it.
kernel component
39
Red Hat Ent erprise Linux 6 .6 Bet a 6 .6 T echnical Not es
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 MB of
RAM
It is possible to avoid the memory trimming by using the disable_mtrr_trim kernel
command line option.
kernel component
On 64-bit PowerPC, the following command may cause kernel panic:
~]# ./perf record -agT -e sched:sched_switch -F 100 -- sleep 3
kernel component
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.
kernel component
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
connectivity
To work around this issue, unload the Brocade bfa driver.
kernel component
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 scsi devices. 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.
kernel component, BZ#6 79 26 2
In Red Hat Enterprise Linux 6.2 and later, due to security concerns, addresses in
/proc/kallsyms and /proc/modules show all zeros when accessed by a non-root
user.
kernel component
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 nomce kernel boot option, which disables machine
check error reporting, or the mce=ignore_ce kernel boot option, which disables
correctable machine check error reporting.
kernel component
4 0
`
Chapt er 6 . Known Issues
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: at PCI 0000:1f:00.0 IRQ 71 using DAC
&
kernel: cciss1: at PCI 0000:02:00.0 IRQ 75 using DAC
If the device name is incorrect, add the pci=bfsort parameter to the kernel command line,
and check again.
kernel component
The minimum firmware version for NIC adapters managed by netxen_nic is 4.0.550. This
includes the boot firmware which is flashed in option ROM on the adapter itself.
kernel component
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.
kernel component
Triggering kdump to capture a vmcore through 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 vmcore from being captured.
kernel component
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)
4 1
Red Hat Ent erprise Linux 6 .6 Bet a 6 .6 T echnical Not es
echo 1 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu3/online
;;
esac
kernel component
In Red Hat Enterprise Linux 6.2, nmi_watchdog registers with the perf subsystem.
Consequently, during boot, the perf subsystem grabs control of the performance counter
registers, blocking OProfile from working. To resolve this, either boot with the
nmi_watchdog=0 kernel parameter set, or run the following command to disable it at run
time:
echo 0 > /proc/sys/kernel/nmi_watchdog
To re-enable nmi-watchdog, use the following command
echo 1 > /proc/sys/kernel/nmi_watchdog
kernel component, BZ#6 039 11
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 LOCKUP and have either ftrace_modify_code or ipi_handler in the
backtrace. To work around this issue, disable NMI watchdog by setting the [ Pobierz całość w formacie PDF ]