Oracle Linux 6 Release Notes
* Updated Feb. 2011 *
===============================================================================
Introduction

This document covers the following topics regarding Oracle Linux 6.

* What's new in this release
* Changes from the upstream release
o Packages modified from upstream release
o Packages removed from upstream release
o New packages added by Oracle
* Kernel
o Unbreakable Enterprise Kernel (x86_64 architecture only)
# Introduction
# New features
* Known Issues
* Technology Preview Features

For the latest updates please refer to the online version of release notes
available at:

http://oss.oracle.com/ol6/docs/

NOTE: An upgrade of Oracle Linux from a beta release is not supported. Further,
an in-place upgrade between major versions of Oracle Linux is not supported.
Oracle does not recommend an upgrade from earlier major versions of Oracle
Linux even though anaconda provides an option to do this upgrade.A fresh
installation is strongly recommended rather than a system upgrade between major
versions. Customers who want to use new features in Unbreakable Enterprise
Kernel can do so without upgrading to Oracle Linux 6 as Oracle Linux 5.6
already includes Unbreakable Enterprise Kernel.

What's new in this release

Oracle Linux 6 includes many new features, including:

* ext4 filesystem
The ext4 filesystem is installed by default.

* XFS
Oracle Linux 6 includes XFS as an optional filesystem.

* ftrace
Ftrace is a tracing framework for analyzing performance and
latency in the kernel.

* Performance Counters for Linux (PCL) and perf
The performance counter subsystem keeps track of hardware and
software events without affecting performance and enables you
to do tracing and performance analysis. Included is a tool
called perf for analysis.

* Powertop
Powertop is a new user space tool that helps you reduce server
power usage by identifying power hungry processes and by
providing recommendations to lower power consumption.

* Latencytop
Latency can be defined as follows: an applications wants to run
and execute code, but is blocked by the kernel because some
required resource is not available. LatencyTOP is a Linux tool
for software developers (both kernel and userspace), aimed at
identifying where system latency occurs, and what kind of
operation or action is causing the latency to happen. By
identifying this, developers can then change the code to avoid
the worst latency hiccups.

* Yum-only access to Unbreakable Linux Network (ULN)
Oracle Linux 6 not longer contains up2date for access to
Unbreakable Linux Network. Instead packages are managed using
Yum. To register with ULN, use the following command:
# uln_register

Additional new features are provided via Unbreakable Enterprise Kernel.

Changes from the Upstream Release

Packages modified from upstream release

The following packages are modified from the upstream release. All changes are
trademark and look/feel related unless otherwise noted below under the specific
package.

* ConsoleKit
* abrt
* anaconda
* basesystem
* compat-glibc
* efax
* filesystem
* firefox
* firstboot
* gdm
* gnome-desktop
* grubby
* gstreamer
* httpd
* initscripts
* iscsi-initiator-utils
* kabi-whitelists
* kabi-yum-plugins
* kdeadmin
* kdebase-workspace
* kexec-tools
* ibus-chewing
* libvirt
* libxml2
* libxslt
* luci
* mkbootdisk
* mod_auth_kerb
* nmap
* nss
* openssl098e
* pilot-link
* piranha
* python-virtinst
* plymouth
* qpid-cpp
* redhat-bookmarks
* redhat-indexhtml
* redhat-lsb
* report
* rhnsd
* rhn-client-tools - updated for Unbreakable Linux Network (ULN) support
* selinux-policy
* setroubleshoot
* setroubleshoot-plugins
* sos
* system-config-date
* system-config-date-docs
* system-config-kickstart
* system-config-network
* system-config-services
* system-config-services-docs
* system-config-users-docs
* system-icon-theme
* tog-pegasus
* wireshark &mdash; ocfs2-related fix
* xsane
* xulrunner
* yum-rhn-plugin

Packages removed from upstream release

The following packages have been removed.

* Red_Hat_Enterprise_Linux-Release_Notes-6-as-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-bn-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-de-DE
* Red_Hat_Enterprise_Linux-Release_Notes-6-en-US
* Red_Hat_Enterprise_Linux-Release_Notes-6-es-ES
* Red_Hat_Enterprise_Linux-Release_Notes-6-fr-FR
* Red_Hat_Enterprise_Linux-Release_Notes-6-gu-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-hi-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-it-IT
* Red_Hat_Enterprise_Linux-Release_Notes-6-ja-JP
* Red_Hat_Enterprise_Linux-Release_Notes-6-kn-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-ko-KR
* Red_Hat_Enterprise_Linux-Release_Notes-6-ml-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-mr-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-or-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-pa-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-pt-BR
* Red_Hat_Enterprise_Linux-Release_Notes-6-ru-RU
* Red_Hat_Enterprise_Linux-Release_Notes-6-si-LK
* Red_Hat_Enterprise_Linux-Release_Notes-6-ta-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-te-IN
* Red_Hat_Enterprise_Linux-Release_Notes-6-zh-CN
* Red_Hat_Enterprise_Linux-Release_Notes-6-zh-TW
* redhat-logos
* redhat-release

New Packages added by Oracle

The following packages have been added to the base release

* kernel-uek
* ocfs2-tools
* oracle-logos
* oracleasm-support
* oraclelinux-release
* oraclelinux-release-notes

Kernel

Oracle Linux 6 ships with two sets of kernel packages:

* Unbreakable Enterprise Kernel [kernel-uek-2.6.32-100.28.5.el6]
o Only available on the x86_64 (64 bit) platform
o Installed and booted by default
* Red Hat compatible Kernel [kernel-2.6.32-71.el6]
o Installed by default

Note: By default, both the Unbreakable Enterprise Kernel and the Red Hat
Compatible Kernel are installed on the x86_64 (64 bit) platform, and the system
boots the Unbreakable Enterprise Kernel by default. If needed, /etc/grub.conf
can be modifed to make the system boot with the Red Hat Compatible Kernel by
default.

Unbreakable Enterprise Kernel (x86_64 architecture only)

The Unbreakable Enterprise Kernel is based on the upstream kernel 2.6.32.21
stable source tree with additional performance improvements, including:

* improved IRQ balancing
* reduced lock contention across the kernel
* improved network I/O via receive packet steering and RDS improvements
* improved virtual memory performance

The Unbreakable Enterprise Kernel is available for the x86_64 architecture and
is the default kernel after installation.

New Features

* OpenFabrics Enterprise Distribution (OFED) 1.5.1
OFED implements Remote Direct Memory Access (RDMA) and kernel
bypass mechanisms to deliver high-efficiency computing, wire-
speed messaging, ultra-low microsecond latencies and fast I/O
for servers, block storage and file systems.

* OCFS2 1.6
The Unbreakable Enterprise Kernel includes the OCFS2 1.6 kernel
module. New features include:
o JBD2 support
o Extended attributes
o POSIX ACLs
o Security attributes
o Metadata checksums
o Indexed directories
o REFLINKs
For more details, see the OCFS2 1.6 User's Guide

* DIF/DIX support
The Linux data integrity framework (DIF) enables applications or
kernel subsystems to attach metadata to I/O operations, allowing
devices that support DIF to verify the integrity before passing them
further down the stack and physically committing them to disk. Data
Integrity Extensions or DIX is a hardware feature that enables
exchange of protection metadata between host operating system and
HBA.

* Tickless kernel
The Unbreakable Enterprise Kernel is tickless. In the tickless
kernel, timer interrupts are performed on demand rather than at a
predetermined frequency. This allows CPUs to stay in a low power
state when the system is idle, reducing overall power consumption

* Task Control Groups (TCG)
TCG can track and group processes into user-defined cgroups so that
the operating system can treat them as whole and perform scheduling,
accounting, and resourceallocation accordingly. For example, using
TCG, you can associate a set of CPU cores and memory nodes to a group
of processes that makeup an application or a group of applications.
This enables subsetting larger systems, more fine grained control
over CPU and memory, and isolation of applications.

* Performance Counters for Linux (PCL)
The performance counter subsystem keeps track of hardware and
software events without affecting performance and enables you to do
tracing and performance analysis. Included is a tool called perf for
analysis.

* SSD Detection
The kernel block layer will detect devices that claim to be
fast, solid state storage and tune itself accordingly. The result of
this detection can be found in:

/sys/block/xxx/queue/rotational

Where xxx is the block device. Echoing a 0 or a 1 into this file will
force the value to off or on. When assuming a device is an SSD, the
block layer will try harder to immediately dispatch the IO to the
device.

* IO affinity
IO affinity ensures processing of a completed IO is handled by the
same CPU that initiated the IO. It can have a fairly large impact on
performance, especially on large NUMA machines. IO affinity is turned
on by default, but it can be controlled via the tunable in /sys/
block/xxx/queue/rq_affinity. For example, the following will turn IO
affinity on:

echo 1> /sys/block/sda/queue/rq_affinity

* Receive packet steering (RPS)
RPS distributes the load of received packet processing across
multiple CPUs. This solution allows protocol processing (e.g. IP and
TCP) to be performed on packets in parallel. This removes a
bottleneck when a single core is saturated processing network
interrupts. To enable receive packet steering for the interface xxx,
place a CPU mask into

/sys/class/net/xxx/queues/rx-0/rps_cpus

The cpu mask takes the same form as the masks for the taskset
command. For example:

echo 0x55> /sys/class/net/eth0/queues/rx-0/rps_cpus

* fallocate()
fallocate() is a new system call which will allow applications to
preallocate space to any file(s) in a file system. Applications can
get a guarantee of space for particular file(s) - even if later the
system becomes full. Using this method of allocation can dramatically
speed up the creation of large files such as those used for virtual
machine images.

Known Issues

1. Incorrect package count (11684244)
Selecting all packages in certain groups during installation
might not show the correct count.

2. kdump does not work with certain controllers and drivers (11680227)
On certain systems, kdump will not work properly. This has
been seen on P400i controllers using cciss and hpsa drivers.

3. hugepages warning messages (9861498)
An application using hugepages may see a warning message like
"Using mlock ulimits for SHM_HUGETLB deprecated." To avoid this
warning, the application should be configured to use
CAP_IPC_LOCK or the process (e.g. Oracle) should be added to
the hugetlb_shm_group.

4. Default reverse path filtering mode affects certain Oracle products (10649976)
Oracle Linux 6 defaults to strict reverse path filtering. Some
Oracle products and network storage devices work more reliably
when using loose reverse path filtering. To enable loose mode
reverse path filtering, issue the following command (assuming
you are changing settings for the network interface called
eth1). The default setting is 1.

sysctl net.ipv4.conf.eth1.rp_filter=2

5. Receive Packet Steering errors for certain network operations (11071685)
Certain network operations that utilize receive packet steering
could cause errors on the system.

6. Syntax error in sample multipath.conf (10650061)
The sample multipath.conf included in Oracle Linux 6 has an
incorrect entry. The path_checker can't be set in the multipath
section. Instead, it must be set in the default or device
sections.

7. Spurious udev messages during restore of a failed path (11682171)
When failed paths are restored in a multipath configuration,
you may see udevd-work error messages in /var/log/messages. The
failed paths do get restored despite these messages.

8. Default NFS v4 mount options
The default NFS mount option has changed to NFS v4. To mount an
NFS volume using NFS v3 (the default in Oracle Linux 5), use
the following mount options:
-o vers=3,mountproto=tcp

9. Setting serial console in a hardware virtualized (HVM) guest
To set the serial console a hardware virtualized (HVM) guest
use following settings in the guest:

o On the kernel boot line in grub.conf, add:
console=tty0 console=ttyS0,57600n8

o add the following to /etc/securetty
ttyS0

o add the following to /etc/sysconfig/init
ACTIVE_CONSOLES=/dev/tty[0-6]

10. Unable to boot a hardware virtualized (HVM) guest that uses
paravirtualized drivers (PVHVM)
As a workaround, install the kernel in an HVM guest without
paravirtualized drivers.

11. Unbreakable Linux Network
After an install of Oracle Linux 6, the screens after the first
reboot will guide you to register your system to the
Unbreakable Linux Network (ULN). If you did not configure your
network during the initial installation, the registration
process to ULN will not succeed. In this case, you should
configure your network by running NetworkManager first (as
root). Then restart the ULN registration by running
uln_register (as root).

12. Console appears to hang while booting on certain systems (10094052)
On some hardware, the console may appear to hang during the
boot process after starting udev. But the system does boot up
properly and is accessible. A workaround to this problem is to
add nomodeset as a kernel boot parameter in /etc/grub.conf:

kernel /vmlinuz-2.6.32-100.28.3.el5.x86_64 ro root=/dev/sd0 nomodeset

13. Unbreakable Enterprise Kernel doesn't contain vmw_pvscsi driver (11697522)
As a workaround, when creating a new VM in VSphere, do not pick
Red Hat Enterprise Linux 6 x86-64 as the OS type but use Oracle Linux 5 x86-64
(or Red Hat Enterprise Linux 5). ESX will then expose the LSI Logic SCSI
controller in the VM and the 2.6.32-100.28.* kernel will see the devices properly.

14. Default IO scheduler
For the Unbreakable Enterprise Kernel, the default IO scheduler
is the 'deadline' scheduler.

For the Red Hat Compatible Kernel, the default IO scheduler
is the 'cfq' scheduler.

15. sched_yield() settings for CFS
For the Unbreakable Enterprise Kernel, kernel.sched_compat_yield=1 by default.
For the Red Hat Compatible Kernel, kernel.sched_compat_yield=0 by default.

16. High IO loads on NFS using mmap may fail (11071875)
In some instances, large IO loads on NFS that use mmap may fail and cause
the kernel to panic with a message like:

kernel BUG at mm/truncate.c:469!

17. Warning message when kdump starts (11688170)
When kdump starts, you may see the following warning message:

WARNING: No modules scsi_mod found for kernel 2.6.32-100.28.5.el6.x86_64,
continuing anyway

This warning can be ignored. The kdump service does get started and a vmcore
does get generated.

18. Encrypted disk feature not supported (11697886)
Configuring the system with an encrypted disk is currently not supported
with the Unbreakable Enterprise Kernel.

Technology Preview Features

The following Technology Preview features are currently not supported under
Oracle Linux 6 and may not be functionally complete:

* fsfreeze
* DIF/DIX support in the Red Hat Compatible Kernel
* Filesystem in Userspace
* LVM Snapshots of Mirrors
* btrfs
* LVM Application Programming Interface (API)
* FS-Cache
* IPv6 support in IPVS
* pacemaker
* certmonger
* ipa-client
* OpenSCAP
* TPM
* Brocade BFA Driver
* SR-IOV on the be2net driver
* Remote Audit Logging
* Linux (NameSpace) Container [LXC]
* Error Detection And Correction (EDAC) driver interface
* libdfp
* Eclipse Plugins

These features are not suitable for production use. However, these features are
included to provide the feature with wider exposure.