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This document contains information on Quarterly Update 4 to the Unbreakable Enterprise Kernel Release 2. This document may be updated after it is released. To check for updates to this document, and to view other Oracle documentation, refer to the Documentation section on the Oracle Technology Network (OTN) Web site:
This document is intended for users and administrators of Oracle Linux. It describes potential issues and the corresponding workarounds you may encounter while using the Unbreakable Enterprise Kernel Release 2 with Oracle Linux 5 and Oracle Linux 6. Oracle recommends that you read this document before installing or upgrading the Unbreakable Enterprise Kernel Release 2.
Document generated on: 2013-07-10 (revision: 1091)
Table of Contents
The Oracle Linux Unbreakable Enterprise Kernel Release Notes provides a summary of the new features, changes, and fixed and known issues in the Unbreakable Enterprise Kernel Release 2.
This document is written for system administrators who want to use the Unbreakable Enterprise Kernel with Oracle Linux. It is assumed that readers have a general understanding of the Linux operating system.
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The latest version of this document and other documentation for this product are available at:
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The Unbreakable Enterprise Kernel Release 2 (UEK R2) is Oracle's second major release of its heavily tested and optimized operating system kernel for Oracle Linux 5 and Oracle Linux 6. It is based on the mainline Linux 3.0 version 3.0.36. See the initial Oracle Unbreakable Enterprise Kernel Release 2 Release Notes (https://oss.oracle.com/ol6/docs/RELEASE-NOTES-UEK2-en.html) for a detailed description of the differences between UEK R2 and the first version of the Unbreakable Enterprise Kernel, which was based on Linux 2.6.32.
The 2.6.39-400.109.1 release is the fourth quarterly driver update release, which also includes bug and security fixes.
The version number displayed by the kernel and on the RPM packages is 2.6.39. This was done to avoid potential breakage of certain low-level utilities of the Oracle Linux distribution (also known as the plumbing) that potentially cannot cope with the new 3.x version scheme. Regular Linux applications are usually neither aware of nor affected by Linux kernel version numbers.
The integrated OpenFabrics Alliance (OFED) 1.5.5 stack, which supports the following InfiniBand hardware on systems with an x86_64 architecture:
Mellanox ConnectX-2 InfiniBand Host Channel Adapters
Sun InfiniBand QDR Host Channel Adapter PCIe #375-3696
The following kernel-level features are implemented for the btrfs file system:
Allow metadata blocks to be larger than the page size (4 KB) and up to 64 KB in size.
BTRFS_IOC_DEVICES_READY, to read device-readiness
Defragmentation does not undo sharing of data blocks between snapshots. Previously, defragmentation could result in more disk space usage because shared data blocks were duplicated.
BTRFS_IOC_SET_LABEL, to get or set a file system
Speed improvements for
fsync direct I/O, and concurrent,
Support for file-hole punching by calling
FALLOC_FL_PUNCH_HOLE flag. Use the
ioctl to detect holes. The
SEEK_DATA options to the
call are not supported.
btrfs-progs-0.20-1.4) will be provided on the
ol6_latest channel for installation by using yum
update. Command-line access to the new features in this package is not
supported on kernel versions prior to this update. If you install this update but not
the updated user-space
btrfs-progs package, programmatic access is
possible for those features that present an
ioctl or other
btrfs-progs package supports the following features
in addition to the kernel-level features:
The -l option to mkfs.btrfs specifies
the leaf size of a file system. The default value of
4k (4 KB)
is recommended for most uses. A value of
32k (16 or 32 KB) can improve performance for some workloads
by reducing metadata fragmentation. The maximum supported size is
64k (64 KB).
The btrfs filesystem label
newlabel command supports labeling or
relabeling of an existing file system. The limitations are that the file system
can only have one device and you must first unmount the file system. The
btrfs filesystem show command displays a file system's
Devices can be replaced at run time by using the btrfs replace start command.
The btrfs filesystem balance command is able change btrfs RAID profiles dynamically.
Collection of device statistics (numbers of read and write failures, checksum errors, and corrupted blocks) by using the btrfs device stats command.
Defragmentation can be cancelled by pressing
Ctrl-C or by
killing the defragmentation process.
Several improvements have been incorporated into the Unbreakable Enterprise Kernel to support Xen usage:
Numerous bug fixes and performance improvements.
xen/privcmd for ARM and PVH by a new
Support for the balloon driver in Xen ARM.
Enhancements to permit PVHVM backend drivers and allow dom0 functionality to be moved to guests.
Implementation of the persistent grant extension to the block ring protocol to improve block protocol scalability for large numbers of physical cores and guests.
Xen Processor Aggregator Device (PAD) added.
The Unbreakable Enterprise Kernel supports a wide range of hardware and devices. In close cooperation with hardware and storage vendors, several device drivers have been updated by Oracle.
ATA over Ethernet (AoE) driver (
aoe) updated to 47q.
NetXtreme II iSCSI driver (
bnx2i) updated to 22.214.171.124d.
NetXtreme II Fibre Channel over Ethernet driver (
updated to 2.3.4.
Cisco FCoE HBA Driver (
fnic) updated to 126.96.36.199.
Blade Engine 2 Open-iSCSI driver (
be2iscsi) updated to
Fibre Channel HBA driver (
lpfc) updated to
LSI Fusion-MPT base driver (
mptbase) updated to
ioctl driver (
LSI Fusion-MPT Fibre Channel host driver (
mptfc) updated to
LSI Fusion-MPT IP Over Fibre Channel driver (
mptlan) updated to
LSI Fusion-MPT SAS driver (
mptsas) updated to
LSI Fusion-MPT SCSI host driver (
mptscsih) updated to
LSI Fusion-MPT SPI host driver (
mptspi) updated to
LSI Fusion-MPT SAS 2.0 driver (
mpt2sas) updated to
MegaRAID SAS driver (
megaraid_sas) updated to
These drivers were first released in UEK R2 Quarterly Update 3.
ConnectX core driver (
mlx4_core) released at 1.0-ofed1.5.5
(x86_64 only). Handles low-level functions such as device initialization and
firmware commands processing, and controls resource allocation so that the
InfiniBand and Ethernet functions can share a device without interfering with each
ConnectX Ethernet driver (
mlx4_en) updated to 1.5.10 (Jan
2013) (x86_64 only). Handles Ethernet-specific functions and plugs into the netdev
ConnectX InfiniBand driver (
mlx4_ib) released at
1.0-ofed1.5.5 (x86_64 only). Handles InfiniBand-specific functions.
Fibre Channel HBA driver (
qla2xxx) updated to
iSCSI driver (
qla4xxx) updated to 5.03.00.02.06.02-uek2.
NetXtreme II network adapter driver (
bnx2) updated to
NetXtreme II 10Gbps network adapter driver (
bnx2x) updated to
Converged Network Interface Card core driver (
Tigon3 Ethernet adapter driver (
tg3) updated to
Blade Engine 2 10Gbps adapter driver (
be2net) updated to
PRO/1000 PCI-Express Gigabit network adapter driver (
updated to 2.3.2-NAPI.
Gigabit Ethernet network adapter driver (
igb) updated to
10 Gigabit PCI-Express network adapter driver (
10 Gigabit Server Adapter virtual function driver (
updated to 2.8.7. The kernel must support Single Root I/O Virtualization
1/10 GbE Converged/Intelligent Ethernet Adapter driver
qlcnic) updated to 188.8.131.52.
QLE81xx network adapter driver (
qlge) updated to
Realtek PCI Express Gigabit Ethernet controller (
VMware VMXNET3 virtual ethernet driver (
vmxnet3) updated to
The following features included in the Unbreakable Enterprise Kernel Release 2 are still under development, but are made available for testing and evaluation purposes.
DRBD (Distributed Replicated Block Device)
A shared-nothing, synchronously replicated block device (RAID1 over network), designed to serve as a building block for high availability (HA) clusters. It requires a cluster manager (for example, pacemaker) for automatic failover.
Kernel module signing facility
Applies cryptographic signature checking to modules on module load, checking the signature against a ring of public keys compiled into the kernel. GPG is used to do the cryptographic work and determines the format of the signature and key data.
Linux Containers (lxc)
Based on the Linux Cgroups and name spaces functionality, containers allow you to
safely and securely run multiple applications or instances of an operating system on a
single host without risking them interfering with each other. Containers are lightweight
and resource-friendly, which saves both rack space and power. In order to get started
with containers, you need to install the
lxc package, which is
included in the package repository of the Unbreakable Enterprise Kernel.
Transcendent Memory (tmem for short) provides a new approach for improving the utilization of physical memory in a virtualized environment by claiming underutilized memory in a system and making it available where it is most needed. From the perspective of an operating system, tmem is fast pseudo-RAM of indeterminate and varying size that is useful primarily when real RAM is in short supply. To learn more about this technology and its use cases, see the Transcendent Memory project page at http://oss.oracle.com/projects/tmem/.
Oracle Linux maintains user-space compatibility with Red Hat Enterprise Linux, which is independent of the kernel version running underneath the operating system. Existing applications in user space will continue to run unmodified on the Unbreakable Enterprise Kernel Release 2 and no re-certifications are needed for RHEL certified applications.
To minimize impact on interoperability during releases, the Oracle Linux team works closely with third-party vendors whose hardware and software have dependencies on kernel modules. However, to allow the introduction of new drivers, there might be instances where changes must be made. Before installing this update, verify the support status of this release with your application vendor.
This chapter describes the fixed and known issues for the Unbreakable Enterprise Kernel Release 2.
Run the yum update command regularly to ensure that the latest bug fixes and security errata are installed on your system.
The following issues have been fixed in this update.
A kernel panic could occur during path failover if one of the paths to a multipathed SCSI device was disabled. (Bug ID 16684527)
Several fixes have been applied to correct race conditions within cgroup movement of newly created, forking, and waking processes. (Bug ID 13740515)
Several fixes have been applied to the OVM API.
A fix has been applied to prevent a kernel panic that could occur when moving OCFS2 extents during defragmentation. (Bug ID 16631951)
btrfs-progs-0.20-1.4), which will be provided on the
ol6_latest channel, fixes a bug where the btrfs subvolume
get-default command listed all existing subvolumes instead of only the
default subvolume. (Bug ID 13815433)
Security fixes for several CVEs, including CVE-2013-2094.
This section describes known issues in this update.
One some systems you might see ACPI-related error messages in
similar to the following:
ACPI Error: [CDW1] Namespace lookup failure, AE_NOT_FOUND ACPI Error: Method parse/execution failed [_SB_._OSC||\||] ACPI Error: Field [CDW3] at 96 exceeds Buffer [NULL] size 64 (bits)]]>
These messages, which are not fatal, are caused by bugs in the BIOS. Contact your system vendor for a BIOS update. (Bug ID 13100702)
/etc/init.d/oracleasm, with the parameter
scandisks can lead to error messages about missing devices similar to
oracleasm-read-label: Unable to open device "
device": No such file or directory
However, the device actually exists. You can ignore this error message, which is
triggered by a timing issue. Only use the
init script to start and stop
oracleasm service. All other options, such as scandisks,
createdisk, are deprecated. For these
and other administrative tasks, use
/usr/sbin/oracleasm instead. (Bug ID
When using the
bnx2x driver in a bridge, disable Transparent Packet
Aggregation (TPA) by including the statement
options bnx2x disable_tpa=1
/etc/modprobe.conf. (Bug ID 14626070)
Together with the UEK R2 kernel in this quarterly update, a new version of the
btrfs-progs-0.20-1.4) will be provided on the
ol6_latest channel. This package enables command-line access to new
btrfs features. If you install this latest version of the
package on a system that does not have an upgraded kernel, most of the new command
functionality supported by the package fails with the error
for device. The exception is the -l option to
mkfs.btrfs, which requires version 2.6.39-400.109.1 or later of the
Unbreakable Enterprise Kernel. Do not use this option with an non-upgraded kernel as
correct functioning of the file system cannot be guaranteed. Although the leaf size
appears to be set successfully, there is a risk of data corruption if you subsequently
use the resulting file system. (Bug ID 16920640)
If you use the --alloc-start option with
mkfs.btrfs to specify an offset for the start of the file system,
the size of the file system should be smaller but this is not the case. It is also
possible to specify an offset that is higher than the device size. This bug is present
in the user-space
btrfs-progs-0.20-1.4). (Bug ID 16946255)
The usage information for mkfs.btrfs reports
raid6 as possible profiles for both
data and metadata. However, the kernel does not support these features and cannot mount
file systems that use them. This bug is present in the user-space
btrfs-progs package (
The btrfs filesystem balance command does not warn that the RAID level can be changed under certain circumstances, and does not provide the choice of cancelling the operation. (Bug ID 16472824)
Converting an existing
ext4 root file system to
btrfs does not carry
over the associated security contexts that are stored as part of a file's extended
attributes. With SELinux enabled and set to enforcing mode, you might experience many
permission denied errors after reboot, and the system might be unbootable. To avoid this
problem, enforce automatic file system relabeling to run at bootup time. To trigger
automatic relabeling, create an empty file named
example, by using touch) in the file system's
directory before rebooting the system after the initial conversion. The presence of this
file instruct SELinux to recreate the security attributes for all files on the file
system. If you forget to do this and rebooting fails, either temporarily disable SELinux
completely by adding
selinux=0 to the kernel boot parameters, or
disable enforcing of the SELinux policy by adding
A failing RAID1 disk can result in a kernel panic with the error message:
BTRFS error (device (null)) in btree_writepage_io_failed_hook:3662: \ IO failure (Error occurred while writing out btree at offset).
(Bug ID 16262571)
The btrfs filesystem defragment command exits with an exit code of 20 even if it succeeds. (Bug ID 13714531)
Commands such as du can show inconsistent results for file
sizes in a
btrfs file system when the number of bytes that is under
delayed allocation is changing. (Bug ID 13096268)
Btrfs has a limit of 237 or fewer hard links to a file from a single directory. The
exact limit depends on the number of characters in the file name. The limit is 237 for a
file with up to eight characters in its file name; the limit is lower for longer file
names. Attempting to create more than this number of links results in the error
Too many links. You can create more hard links to the same file
from another directory. (Bug ID 16278563)
If you run the btrfs quota enable command on a non-empty file system, any existing files do not count toward space usage. Removing these files can cause usage reports to display negative numbers and the file system to be inaccessible. The workaround is to enable quotas immediately after creating the file system. If you have already written data to the file system, it is too late to enable quotas. (Bug ID 16569350)
The btrfs quota rescan command is not currently implemented. The command does not perform a rescan and returns without displaying any message.
The functionality to limit the space that is available to a quota group before compressing the subvolume is not yet implemented. The -c option (limit the space after compression) to the btrfs qgroup limit command is implicitly enabled. (Bug ID 16569387)
The copy-on-write nature of btrfs means that every operation on the file system initially requires disk space. It is possible that you cannot execute any operation on a disk that has no space left; even removing a file might not be possible. The workaround is to run fsync before retrying the operation. If this does not help, remount the file system with the -o nodatacow option and delete some files to free up space. See https://btrfs.wiki.kernel.org/index.php/ENOSPC.
When running Oracle Linux with UEK R2, you might see error messages in
/var/log/messages similar to this
microcode: CPU0 update to revision 0x6b failed.
You can ignore this warning. You do not need to upgrade the microcode for virtual CPUs as presented to the guest. (Bug ID 12576264, 13782843)
If DHCP lease negotiation takes more than 5 seconds at boot time, the following message is displayed:
X: failed. No link present. Check cable?
If the ethtool eth
X command confirms that
the interface is present, edit
N is a value greater than 5 seconds (for example, 30 seconds).
Alternatively, use NetworkManager to configure the interface. (Bug ID 16620177)
You can safely ignore the following firmware warning message that might be displayed on some Sun hardware:
[Firmware Warn]: GHES: Poll interval is 0 for generic hardware error source: 1, disabled.
(Bug ID 13696512)
The Unbreakable Enterprise Kernel uses the
deadline scheduler as the
default I/O scheduler. For the Red Hat Compatible Kernel, the default I/O scheduler is the
You might see the following warning messages if you use the ibportstate disable command to disable a switch port:
ibwarn:  _do_madrpc: recv failed: Connection timed out ibwarn:  mad_rpc: _do_madrpc failed; dport (Lid 38) ibportstate: iberror: failed: smp set portinfo failed
You can safely ignore these warnings. (Bug ID 16248314)
The following message might appear in
WARNING! power/level is deprecated; use power/control instead.
The USB subsystem in UEK R2 deprecates the
attribute in favor of the
power/control attribute. The
libfprint fingerprinting library triggers this warning via
udev rules that try to use the old attribute first. You can safely
ignore this warning. The setting of the appropriate power level still succeeds. (Bug ID
After upgrading to UEK R2, the NVIDIA driver upgrade script does not correctly blacklist
the Nouveau kernel driver. To blacklist the driver, append
nouveau.modeset=0 to the kernel boot parameters in
You can safely ignore the following warning messages in
/var/log messages if you see them on a non-NUMA system:
kernel: NUMA: Warning: node ids are out of bound, from=-1 to=-1 distance=10 hcid: Register path:/org/bluez fallback:1 kernel: No NUMA configuration found
(Bug ID 13711370)
You can safely ignore the following error message:
Error: Driver 'pcspkr' is already registered, aborting...
The message arises from an alias conflict between
pcspkr. To prevent the message from being displayed, add the following
(Bug ID 10355937)
For the Unbreakable Enterprise Kernel,
set by default. For the Red Hat Compatible Kernel,
kernel.sched_compat_yield=0 is used by default.
Releases of Oracle Linux prior to Oracle Linux 5 supplied a hugemem kernel to allow a system to address up to 64 GB of memory in 32-bit mode. The hugemem kernel is no longer available in Oracle Linux 5 and later releases.
The Unbreakable Enterprise Kernel (UEK) supports a maximum of 16 GB of memory for 32-bit kernels on bare metal and hardware virtualized machine (HVM) systems, and 8 GB for fully paravirtualized machine (PVM) systems. 32-bit PVM guest operating systems must be located in the first 128 GB of physical memory on the host.
The Red Hat Compatible Kernel (RHCK) has the same limitations, except that PVM systems can have up to 16 GB of memory. The limitation of 8 GB for PVM on UEK was chosen for reasons of reliability.
A 32-bit system uses the PAE (physical address extension) memory feature to map physical memory beyond 4 GB into the 32-bit address space that is available to each process. A 64-bit system can address memory beyond 4 GB without requiring an extra layer of memory abstraction.
Oracle Linux on x86_64 includes 32-bit libraries, which allow applications built for both 64-bit and 32-bit Linux to run on the same system. This capability provides scalability to virtually unlimited memory sizes, while retaining the ability to run 32-bit applications. Oracle recommends this configuration for any system with more than 4 GB of memory. (Bug ID 16974301)
A message similar to the following might be recorded in
/var/log/messages at boot
pid/oom_adj is deprecated, please use /proc/
udev process uses the deprecated
interface to prevent it from being killed if the system runs short of memory. You can safely
ignore the message as the action still succeeds. To prevent the message from occurring,
install the package
or higher for Oracle Linux 6, or
udev-095-184.108.40.206.el5. or higher
for Oracle Linux 5. (Bug ID 13655071 and 13712009)
When booting UEK R2 as a PVHVM guest, you can safely ignore the following kernel message:
register_vcpu_info failed: err=-38
(Bug ID 13713774)
Under Oracle VM Server 3.1.1, migrating a PVHVM guest that is running the UEK R2 Quarterly Update 4 kernel causes a disparity between the date and time as displayed by date and hwclock. The workaround post migration is either to run the command hwclock --hctosys on the guest or to reboot the guest. (Bug ID 16861041)
The Unbreakable Enterprise Kernel Release 2 Quarterly Update 4 can be installed on Oracle Linux 5 Update 8 or newer, as well as Oracle Linux 6 Update 2 or newer, both running either the Red Hat compatible kernel or a previous version of the Unbreakable Enterprise Kernel. If you are still running an older version of Oracle Linux, first update your system to the latest available update release.
The kernel images are available as binary RPM packages from dedicated channels on Oracle's Unbreakable Linux Network (ULN) as well as the Oracle Public Yum repository. Four channels are available:
Oracle Linux 5 (x86):
Oracle Linux 5 (x86_64):
Oracle Linux 6 (x86):
Oracle Linux 6 (x86_64):
If your system is registered with ULN, make sure you subscribe it to the appropriate
For Oracle Public Yum, the appropriate
UEK_latest channel is
automatically enabled in the yum respiratory file under
when you install Oracle Linux 5 update 9 or later and Oracle Linux 6 update 3 or later.
To upgrade an existing Oracle Linux 5 or Oracle Linux 6 installation to the latest UEK
R2, enable the appropriate
UEK_latest channel and run yum
For detailed instructions on how to download and install the Unbreakable Enterprise Kernel on Oracle Linux see the Getting Started with the Unbreakable Enterprise Kernel for Oracle Linux document on the Oracle Technology Network (OTN) at http://www.oracle.com/technetwork/articles/servers-storage-admin/uek-rel2-getting-started-1555632.html.
If you have questions regarding configuring or using yum to install updates, refer to the Oracle Linux Administrator's Solutions Guide at http://docs.oracle.com/cd/E37670_01/index.html.
For information about using ULN, see the Oracle Linux Unbreakable Linux Network User's Guide at http://docs.oracle.com/cd/E37670_01/index.html.
The kernel's source code is available via a public git source code repository at http://oss.oracle.com/git/?p=linux-uek-2.6.39.git.