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The Release Notes provide high-level coverage of the improvements and
additions that have been implemented in Red Hat Enterprise Linux 6.3.
For detailed documentation on all changes to Red Hat Enterprise Linux
for the 6.3 update, refer to the Technical Notes.
Red Hat Enterprise Linux minor releases are an aggregation of
individual enhancement, security and bug fix errata. The Red Hat
Enterprise Linux 6.3 Release Notes documents the major changes made to
the Red Hat Enterprise Linux 6 operating system and its accompanying
applications for this minor release. Detailed notes on changes (that is,
bugs fixed, enhancements added, and known issues found) in this minor
release are available in the Technical Notes.
The Technical Notes document also contains a complete list of all
currently available Technology Previews along with packages that provide
The online Red Hat Enterprise Linux 6.3 Release Notes, which are located online here,
are to be considered the definitive, up-to-date version. Customers with
questions about the release are advised to consult the online Release and Technical Notes for their version of Red Hat Enterprise Linux.
Thin-provisioning and scalable snapshot capabilities
The dm-thinp targets, thin and thin-pool,
provide a device-mapper device with thin-provisioning and scalable
snapshot capabilities. This feature is available as a Technology
Preview. For more information on the newly-introduced LVM thin
provisioning, refer to Chapter 9, Storage.
sysfs mbox interface deprecated
The lpfc driver is deprecating the sysfsmbox interface as it is no longer used by the Emulex tools. Read and write operations are now stubbed out and only return the -EPERM (Operation not permitted) symbol.
Red Hat Enterprise Linux 6.3 adds support for mount options to restrict access to /proc/<PID>/ directories. One of the new options is called hidepid= and its value defines how much information about processes is provided to non-owners. The gid=
option defines a group that gathers information about all processes.
Untrusted users, which are not supposed to monitor tasks in the whole
system, should not be added to the group.
O_DIRECT flag support
Support for the O_DIRECT flag for
files in FUSE (File system in Userspace) has been added. This flag
minimizes cache effects of the I/O to and from a file. In general, using
this flag degrades performance, but it is useful in special situations,
such as when applications do their own caching.
CONFIG_STRICT_DEVMEM enabled on PowerPC
In Red Hat Enterprise Linux 6.3, the CONFIG_STRICT_DEVMEM configuration option is enabled by default for the PowerPC architecture. This option restricts access to the /dev/mem
device. If this option is disabled, userspace access to all memory is
allowed, including kernel and userspace memory, and accidental memory
(write) access could potentially be harmful.
In Red Hat Enterprise Linux 6.3, the high-resolution timer's capacity
to remap the HPET registers into the memory of a user process has been
Improved performance on large systems
A number of patches have been applied to the kernel in Red Hat
Enterprise Linux 6.3 to improve overall performance and reduce boot time
on extremely large systems (patches were tested on a system with 2048
cores and 16 TB of memory).
rdrand kernel support
The Intel Core i5 and i7 processors (formerly code-named Ivy Bridge) support a new rdrand
instruction to quickly generate random numbers. The kernel shipped in
Red Hat Enterprise Linux 6.3 utilizes this instruction to provide quick
random number generation.
UEFI support for persistent storage
Persistent storage (pstore), a file system interface for platform dependent persistent storage, now supports UEFI.
CPU family specific container files
Support for CPU family specific container files has been added. Starting with AMD family 15h processors, a container such as microcode_amd_fam15h.bin is now loaded for the aforementioned family of processors.
USB 3.0 support
Red Hat Enterprise Linux 6.3 includes full USB 3.0 support.
kdump/kexec kernel dumping mechanism for IBM System z
In Red Hat Enterprise Linux 6.3, the kdump/kexec kernel dumping
mechanism is enabled for IBM System z systems as a Technology Preview,
in addition to the IBM System z stand-alone and hypervisor dumping
mechanism. The auto-reserve threshold is set at 4 GB; therefore,
any IBM System z system with more than 4 GB of memory has the
kexec/kdump mechanism enabled.
Sufficient memory must be available because kdump reserves
approximately 128 MB as default. This is especially important when
performing an upgrade to Red Hat Enterprise Linux 6.3. Sufficient disk
space must also be available for storing the dump in case of a system
crash. Kdump is limited to DASD or QETH networks as dump devices until
kdump on SCSI disk is supported.
The following warning message may appear when kdump is initialized:
..no such file or directory
This message does not impact the dump functionality and can be ignored. You can configure or disable kdump via /etc/kdump.conf, system-config-kdump, or firstboot.
Module-accessible interface for ftrace
The ftrace function tracer now allows modules and all users to make use of the ftrace function tracing utility. For more information, refer to the following man pages:
Tracing of multi-threaded processes
When tracing processes with more than one thread, the ltrace
utility would neglect to trace threads other than the main thread. But
because threads share address space, those other threads would still see
breakpoints distributed by ltrace. Consequently, those threads would be killed by a SIGTRAP
signal. Red Hat Enterprise Linux 6.3 includes thread-awareness and
breakpoint handling mechanisms. Support for tracing of multi-threaded
processes is now on par with tracing single-threaded process.
Cross Memory Attach
Cross Memory Attach provides a mechanism to reduce the number of data
copies needed for intra-node inter-process communication. In
particular, this allows MPI libraries doing intra-node communication to
do a single copy of the message rather than a double copy of the message
via shared memory. This technique has been employed in the past through
multiple, unique driver-based implementations. The implementation
introduced in Red Hat Enterprise Linux 6.3 provides a general solution
for this functionality. In addition, it provides a layer of abstraction
for device driver writers who wish to exploit these functions without
having to modify their corresponding implementations when there are
changes in the memory management subsystem.
Spinning mutex performance enhancement for IBM System z
Red Hat Enterprise Linux 6.3 enhances the usage of mutexes.
Additional information provided to the scheduler allows for more
efficient and less costly decisions when optimizing processor cycles
depending on the usage of mutexes, thread scheduling, and the status of
the physical and virtual processors. The status of a thread owning a
locked mutex is examined and waiting threads are not scheduled unless
the first thread is scheduled on both a virtual and a physical
Enhanced DASD statistics for PAV and HPF for IBM System z
Red Hat Enterprise Linux 6.3 enables improved diagnosis of PAV
(Parallel Access Volume) and HPF (High Performance Ficon) environments
to analyze and tune the DASD performance on a system, for example, to
give recommendations regarding the number of alias devices or the usage
of PAV versus HyperPAV.
OSA concurrent software/hardware trap for IBM System z
With Red Hat Enterprise Linux 6.3, collective problem analysis
through consolidated dumps of software and hardware is enabled. A
command can be used to generate qeth or qdio trace data and to trigger the internal dump of an OSA device.
Added ability to switch between two graphics cards
The CONFIG_VGA_SWITCHEROO configuration option is now enabled by default to allow switching between two graphics cards.
KEXEC_AUTO_THRESHOLD lowered to 2 GB
With Red Hat Enterprise Linux 6.3, the crashkernel=auto
parameter changed the default kdump enabling threshold from 4 GB
to 2 GB. This means that any machine that has 2 GB (or more)
of memory will have the kdump feature enabled on its systems.
Available memory in the system is rounded up to 128 MB when
calculating the 2 GB threshold for deciding whether to enable kdump
or not. If a system has 1920 MB (2G-128M) RAM available, kdump is
Run the following commands if you wish to disable kdump (for example, due to memory constraints):
To stop the kdump service, execute the following command:
~]# service kdump stop
To disable the kdump service, execute the following command:
~]# chkconfig kdump off
To return memory previously reserved for kdump back to the system, execute the following command:
~]# echo 0 > /sys/kernel/kexec_crash_size
Chapter 2. Device Drivers
BFA driver fully supported
The Brocade BFA Fibre Channel and FCoE driver is no longer a
Technology Preview. In Red Hat Enterprise Linux 6.3 the BFA driver is
BNA driver fully supported
The Brocade BNA driver for Brocade 10Gb PCIe ethernet Controllers is
no longer a Technology Preview. In Red Hat Enterprise Linux 6.3 the BNA
driver is fully supported.
SR-IOV on the be2net driver
The SR-IOV functionality of the Emulex be2net
driver is considered a Technology Preview in Red Hat Enterprise Linux
6.3. You must meet the following requirements to use the latest version
of SR-IOV support:
You must run the latest Emulex firmware (revision 4.1.417.0 or later).
The server system BIOS must support the SR-IOV functionality and have virtualization support for Direct I/O VT-d.
You must use the GA version of Red Hat Enterprise Linux 6.3.
SR-IOV runs on all Emulex-branded and OEM variants of BE3-based hardware, which all require the be2net driver software.
Red Hat Enterprise Linux 6.3 includes the mtip32xx driver which adds support for Micron RealSSD P320h PCIe SSD drives.
The lpfc driver for Emulex Fibre Channel Host Bus Adapters has been updated to version 220.127.116.11.2p.
The mptfusion driver has been updated to version 3.04.20.
The bnx2fc for the Broadcom Netxtreme II 57712 chip has been updated to version 1.0.11.
The qla2xxx driver for QLogic Fibre Channel HBAs has been updated to version 8.04.00.02.06.3-k. The qla2xxx
driver update for Red Hat Enterprise Linux 6.3 now takes advantage of
the common code in the SCSI mid-layer that handles queue-full status
messages returned from a target port. Before, this code resided in the qla2xxx driver itself. To maintain API compatibility, stubs for the ql2xqfulltracking and ql2xqfullrampup module parameters have been left in the driver itself.
In addition, this update also adds support for ISP82xx and ISP83xx, and adds the dynamic logging functionality.
The qla4xxxx has been updated to version 5.02.00.00.06.03-k1, which adds support for displaying port_state, port_speed, and targetalias in the sysfs file system.
The megaraid driver has been updated to version 00.00.06.14-rh1.
The ipr driver for IBM Power Linux RAID SCSI HBAs has been updated to enable the SAS VRAID functions.
The cciss driver has been updated to add older controllers to the kdump blacklist.
The hpsa driver has been updated to the version 2.0.2-4 to add older controllers to the kdump blacklist.
The bnx2i driver for Broadcom NetXtreme II iSCSI has been updated to version 18.104.22.168.
The mpt2sas driver has been updated to version 12.101.00.00, adding NUNA I/O support which uses multi-reply queue support of HBAs.
The mptsas driver has been updated to add the following device ID: SAS1068_820XELP.
The Brocade BFA FC SCSI driver (bfa driver) has been updated.
The be2iscsi driver for ServerEngines BladeEngine 2 Open iSCSI devices has been updated.
The ahci.c driver have been updated to add the AHCI-mode SATA DeviceID for the Intel DH89xxCC PCH.
The isci driver has been updated to version 1.1 to pick up the latest Intel hardware support, enhancements, and bug fixes.
The isci sata driver has been updated to add T10 DIF support.
The libfc, libfcoe, and fcoe drivers have been updated to fix various bugs and add several enhancements.
The libsas driver has been updated.
The qib driver for TrueScale HCAs has been updated.
The libata module has been updated to fix various bugs.
The dm-raid code of the md driver has been updated to include flush support.
The following drivers have been updated to the latest version: ahci, md/bitmap, raid0, raid1, raid10, and raid456.
The aacraid driver has been updated to version 1.1-7.
The netxen driver for NetXen Multi port (1/10) Gigabit Network has been updated to version 4.0.77 or greater.
The bnx2x driver has been updated to version 7.2.16 to include support for the 578xx family of chips.
The be2net driver for ServerEngines BladeEngine2 10Gbps network devices has been updated to version 22.214.171.124r.
The ixgbevf driver has been updated to version 2.2.0-k to include the latest hardware support, enhancements, and bug fixes.
The cxgb4 driver for Chelsio Terminator4 10G Unified Wire Network Controllers has been updated.
The cxgb3 driver for the Chelsio T3 Family of network devices has been updated.
The ixgbe driver for Intel 10
Gigabit PCI Express network devices has been updated to version 3.6.7-k
to include the latest hardware support, enhancements, and bug fixes.
The e1000e driver for Intel PRO/1000 network devices has been updated.
The e1000 driver for Intel PRO/1000 network devices has been updated.
The e100 driver has been updated.
The enic driver for Cisco 10G Ethernet devices has been updated to version 126.96.36.199, adding SR-IOV support.
The igbvf driver (Intel Gigabit Virtual Function Network driver) has been updated to version 2.0.1-k.
The igb driver for Intel Gigabit
Ethernet Adapters has been updated to version 3.2.10-k, providing
up-to-date hardware support, enhancements, and bug fixes.
The bnx2 driver for the NetXtreme II 1 Gigabit Ethernet controllers has been updated to version 1.0.11.
The tg3 driver for Broadcom Tigon3 Ethernet devices has been updated to version 3.120+.
The qlcnic driver for the HP NC-Series QLogic 10 Gigabit Server Adapters has been updated to version 5.0.26.
The bna driver has been updated.
The r8169 driver has been updated to
add support for the latest Realtek NICs (8168D/8168DP/8168E/8168EV) and
increase reliability of older NICs.
The qlge driver has been updated to version 1.00.00.30.
The cnic driver has been updated to
version 2.5.9, which improves error recovery on bnx2x devices, adds FCoE
parity error recovery, increases the maximum amount of FCoE sessions,
and adds other enhancements.
The iwl6000 and iwlwifi drivers have been updated to add support for the Intel Centrino Wireless-N 6235 series of Wi-Fi adapters. The iwlwifi also adds an option with 5GHz band can be disabled.
The wireless LAN subsystem has been updated. It introduces the dma_unmap state API and adds a new kernel header file: include/linux/pci-dma.h.
The rt2800usb/rt2x00 driver has been updated to add support for D-Link DWA-127 11N USB Wireless Network Card.
The atl1c driver has been updated to
the latest upstream version, which adds support for Atheros AR8151 v2
and Atheros AR8152 PCI-E Gigabit Ethernet Controllers.
The i915 driver has been updated.
Various graphics drivers have been updated with DRM support rebased to version 3.3-rc2.
The Wacom driver has been updated, deprecating the wacompl package and obsoleting the wdaemon package.
The ALSA HDA audio driver has been updated to enable or improve support for new chipsets and HDA audio codecs.
The btusb driver has been updated to include support for the Broadcom BCM20702A0 single-chip bluetooth processor.
The k10temp driver from the hwmon subsystem has been updated to add support for AMD family 12h/14h/15h of CPUs.
The ALPS Touchpad driver has been updated to add support for ALPS
Touchpad protocol versions 3 and 4, and add support for touchpads with
The jsm driver has been updated to add Enhanced Error Handling (EEH).
The mlx4_en driver has been updated to version 2.0.
The mlx4_core driver has been updated to version 1.1.
Chapter 3. Networking
QFQ queuing discipline
In Red Hat Enterprise Linux 6.3, the tc
utility has been updated to work with the Quick Fair Scheduler (QFQ)
kernel features. Users can now take advantage of the new QFQ traffic
queuing discipline from userspace. This feature is considered a
rdma_bw and rdma_last utilities deprecated
The rdma_bw and rdma_lat utilities (provided by the perftest package) are now deprecated and will be removed from the perftest package in a future update. Users should use the following utilities instead: ib_write_bw, ib_write_lat, ib_read_bw, and ib_read_lat.
Enhancements in the configuration tool for IBM System z network devices
With Red Hat Enterprise Linux 6.3, the System z qethconf tool provides information messages when a change of attributes did not work as expected.
IPv6 support for qetharp tool for IBM System z
Red Hat Enterprise Linux 6.3 adds IPv6 support to the qetharp
tool for inspection and modification of the ARP cache of HiperSockets
(real and virtual) operated in layer 3 mode. For real HiperSockets, the
tool queries and shows the IPv6 address, and for guest LAN HiperSockets,
it queries and shows IPv6 to MAC address mappings.
Maximum number of session slots
In Red Hat Enterprise Linux 6.3, NFSv4 introduces a module/kernel boot parameter, nfs.max_session_slots,
which sets the maximum number of session slots the NFS client will
attempt to negotiate with the server. This limits the number of
simultaneous RPC requests that the client can send to the NFSv4 server.
Note that setting this value higher than max_tcp_slot_table_limit has no effect.
Chapter 4. Resource Management
Network priority cgroup resource controller
Red Hat Enterprise Linux 6.3 introduces the Network Priority (net_prio)
resource controller, which provides a way to dynamically set the
priority of network traffic per each network interface for applications
within various cgroups. For more information, refer to the Resource Management Guide.
OOM control and notification API for cgroups
The memory resource controller implements an Out-of-Memory (OOM)
notifier which uses the new notification API. When enabled (by executing
echo 1 > memory.oom_control), an application is notified via eventfd when an OOM occurs. Note that OOM notification does not function for root cgroups.
New numad package
The numad package provides a daemon for
NUMA (Non-Uniform Memory Architecture) systems that monitors NUMA
characteristics. As an alternative to manual static CPU pinning and
memory assignment, numad provides dynamic
adjustment to minimize memory latency on an ongoing basis. The package
also provides an interface that can be used to query the numad daemon for the best manual placement of an application. The numad package is introduced as a Technology Preview.
Chapter 5. Authentication and Interoperability
Support for central management of SSH keys
Previously, it was not possible to centrally manage host and user SSH
public keys. Red Hat Enterprise Linux 6.3 includes SSH public key
management for Identity Management servers as a Technology Preview.
OpenSSH on Identity Management clients is automatically configured to
use public keys which are stored on the Identity Management server. SSH
host and user identities can now be managed centrally in Identity
SELinux user mapping
Red Hat Enterprise Linux 6.3 introduces the ability to control the
SELinux context of a user on a remote system. SELinux user map rules can
be defined and, optionally, associated with HBAC rules. These maps
define the context a user receives depending on the host they are
logging into and the group membership. When a user logs into a remote
host which is configured to use SSSD with the Identity Management
backend, the user's SELinux context is automatically set according to
mapping rules defined for that user. For more information, refer to http://freeipa.org/page/SELinux_user_mapping. This feature is considered a Technology Preview.
Multiple required methods of authentication for sshd
SSH can now be set up to require multiple ways of authentication
(whereas previously SSH allowed multiple ways of authentication of which
only one was required for a successful login); for example, logging in
to an SSH-enabled machine requires both a passphrase and a public key to be entered. The RequiredAuthentications1 and RequiredAuthentications2 options can be configured in the /etc/ssh/sshd_config file to specify authentications that are required for a successful log in. For example:
For more information on the aforementioned /etc/ssh/sshd_config options, refer to the sshd_config man page.
SSSD support for automount map caching
In Red Hat Enterprise Linux 6.3, SSSD includes a new Technology
Preview feature: support for caching automount maps. This feature
provides several advantages to environments that operate with autofs:
Cached automount maps make it easy for a client machine to perform
mount operations even when the LDAP server is unreachable, but the NFS
server remains reachable.
When the autofs daemon is configured to look up automount maps via SSSD, only a single file has to be configured: /etc/sssd/sssd.conf. Previously, the /etc/sysconfig/autofs file had to be configured to fetch autofs data.
Caching the automount maps results in faster performance on the client and lower traffic on the LDAP server.
Change in SSSD debug_level behavior
SSSD has changed the behavior of the debug_level option in the /etc/sssd/sssd.conf file. Previously, it was possible to set the debug_level option in the [sssd]
configuration section and the result would be that this became the
default setting for other configuration sections, unless they explicitly
Several changes to internal debug logging features necessitated that the debug_level
option must always be specified independently in each section of the
configuration file, instead of acquiring its default from the [sssd] section.
As a result, after updating to the latest version of SSSD, users may
need to update their configurations in order to continue receiving debug
logging at the same level. Users that configure SSSD on a per-machine
basis can use a simple Python utility that updates their existing
configuration in a compatible way. This can be accomplished by running
the following command as root:
This utility makes the following changes to the configuration file: it checks to see if the debug_level option was specified in the [sssd] section. If so, it adds that same level value to each other section in the sssd.conf file for which debug_level is unspecified. If the debug_level option already exists explicitly in another section, it is left unchanged.
Users who rely on central configuration management tools need to make these same changes manually in the appropriate tool.
New ldap_chpass_update_last_change option
A new option, ldap_chpass_update_last_change, has been added to SSSD configuration. If this option is enabled, SSSD attempts to change the shadowLastChange
LDAP attribute to the current time. Note that this is only related to a
case when the LDAP password policy is used (usually taken care of by
LDAP server), that is, the LDAP extended operation is used to change the
password. Also note that the attribute has to be writable by the user
who is changing the password.
Chapter 6. Subscription Management
Migration from RHN Classic to certificate-based RHN
Subscription Manager now disables gpgcheck for any repositories it manages which have an empty gpgkey. To re-enable the repository, upload the GPG keys, and ensure that the correct URL is added to your custom content definition.
Firstboot System Registration
In Red Hat Enterprise Linux 6.3, during firstboot system registration, registering to Certificate-based Subscription Management is now the default option.
Server side deletes
System profiles are now unregistered when they are deleted from the
Customer Portal so that they no longer check in with certificate-based
Preferred service levels
Subscription manager now allows users to associate a machine with a preferred Service Level which impacts the auto subscription and healing logic. For more information on service levels, refer to the Red Hat Enterprise Linux 6 Deployment Guide.
Limiting updates to a specific minor release
Subscription manager now allows a user to select a specific release
(for example, Red Hat Enterprise Linux 6.2), which will lock a machine
to that release. Prior to this update, there was no way to limit package
updates in the event newer packages became available as part of a later
minor release (for example, Red Hat Enterprise Linux 6.3).
KVM scalability enhancements in Red Hat Enterprise Linux 6.3 include:
The maximum supported virtual guest size increased from 64 to 160 virtual CPUs (vCPUs).
The maximum supported memory in a KVM guest increased from 512 GB to 2 TB.
KVM support for new Intel and AMD processors
KVM in Red Hat Enterprise Linux 6.3 includes support for:
Intel Core i3, i5, i7 and other processors formerly code named “Sandy Bridge”,
and new AMD family 15h processors (code named “Bulldozer”).
The new CPU model definitions in KVM provide the necessary new
processor enablement to KVM host and the virtualized guests. This
ensures that KVM Virtualization derives the performance benefits
associated with the new processors, and takes advantage of the new
instructions in the latest CPUs.
KVM “Steal Time” support
Steal time is the time that a virtual CPU
waits for a real CPU while the hypervisor is servicing another virtual
processor. KVM virtual machines can now calculate and report steal time,
visible through tools like top and vmstat, which provides a guest with accurate CPU utilization data.
The KVM steal time feature provides accurate data to a guest
regarding CPU utilization and virtual machine performance. Large amounts
of steal time indicates that the virtual machine performance is
curtailed by the CPU time assigned to the guest by the hypervisor. The
user can relieve the performance issues caused by CPU contention by
running fewer guests on the host or by increasing the CPU priority of
the guest. The KVM steal time value provides users with data to allow
them to take the next step in improving their application run-time
Improved access to qcow2 disk images
KVM in Red Hat Enterprise Linux 6.3 improved the access to qcow2 disk images (qcow2
is the default format) by making it more asynchronous, thus avoiding
vCPU stalls and enhancing the overall performance during disk I/O.
New qemu-guest-agent subpackage
The qemu-kvm has a new sub-package called qemu-guest-agent.
When running Red Hat Enterprise Linux 6.3 guests with this package
installed, properly configured Red Hat Enterprise Linux 6.3 hosts can
send new commands to the guest such as: guest-sync, guest-ping, guest-info, guest-shutdown, and guest-suspend-*.
KVM can now virtualize Intel's performance monitoring unit (PMU) to allow virtual machines to use performance monitoring.
Note that the -cpu host flag must be set when using this feature.
With this feature, Red Hat virtualization customers running Red Hat
Enterprise Linux 6 guests can use the CPU's PMU counter while using the
performance tool for profiling. The virtual performance monitoring unit
feature allows virtual machine users to identify sources of performance
problems in their guests, thereby improving the ability to profile a KVM
guest from the host.
This feature is a Technology Preview in Red Hat Enterprise Linux 6.3
and is only supported with guests running Red Hat Enterprise Linux 6.
Dynamic virtual CPU allocation
KVM in Red Hat Enterprise Linux 6.3 now supports dynamic virtual CPU
allocation, also called vCPU hot plug, to dynamically manage capacity
and react to unexpected load increases on their platforms during
The virtual CPU hot-plugging feature gives system administrators the
ability to dynamically adjust CPU resources in a guest. Because a guest
no longer has to be taken offline to adjust the CPU resources, the
availability of the guest is increased.
This feature is a Technology Preview in Red Hat Enterprise Linux 6.3.
Currently, only the vCPU hot-add functionality works. The vCPU hot
unplug feature is not yet implemented.
KVM Virtualization's storage stack has been improved with the
addition of virtio-SCSI (a storage architecture for KVM based on SCSI)
capabilities. Virtio-SCSI provides the ability to connect directly to
SCSI LUNs and significantly improves scalability compared to virtio-blk.
The advantage of virtio-SCSI is that it is capable of handling hundreds
of devices compared to virtio-blk which can only handle 28 devices and
exhausts PCI slots.
Virtio-SCSI is now capable of inheriting the feature set of the target device with the ability to:
attach a virtual hard drive or CD through the virtio-scsi controller,
pass-through a physical SCSI device from the host to the guest via the QEMU scsi-block device,
and allow the usage of hundreds of devices per guest; an improvement from the 28-device limit of virtio-blk.
This feature is a Technology Preview in Red Hat Enterprise Linux 6.3.
Support for in-guest S4/S3 states
KVM's power management features have been extended to include native
support for S4 (suspend to disk) and S3 (suspend to RAM) states within
the virtual machine, speeding up guest restoration from one of these low
power states. In earlier implementations guests were saved or restored
to or from a disk or memory that was external to the guest, which
Additionally, guests can be awakened from the S3 state with events from a remote keyboard through SPICE.
This feature is a Technology Preview and is disabled by default in Red Hat Enterprise Linux 6.3. To enable it, select the /usr/share/seabios/bios-pm.bin file for the VM bios instead of the default /usr/share/seabios/bios.bin file.
The native, in-guest S4 (suspend to disk) and S3 (suspend to RAM)
power management features support the ability to perform suspend to disk
and suspend to RAM functions in the guest (as opposed to the host),
reducing the time needed to restore a guest by responding to simple
keyboard input. This also removes the need to maintain an external
memory-state file. This capability is supported on Red Hat Enterprise
Linux 6.3 guests and Windows guests running on any hypervisor capable of
supporting S3 and S4.
Red Hat Enterprise Linux 6.3 adds support for Time Stamp Counter
(TSC) scaling to KVM for AMD Virtualization (AMD-V). This feature is
capable of emulating a given TSC frequency on a KVM guest.
Support for perf-kvm
Support for the perf-kvm tool, which provides the ability to monitor guest performance from host, has been added. For more information, refer to the perf-kvm man page.
USB 2.0 redirection support
Spice builds on KVM USB 2.0 host adapter emulation support, and
enables remote USB redirection support that allows virtual machines
running on servers to use remotely plugged USB devices on the client
Controlling up/down link states
libvirt is now
capable of controlling the state (up or down) of a link of the guest
virtual network interfaces. This allows users to perform testing and
simulation as though plugging and unplugging the network cable from the
interface. This feature also lets users isolate guests in case any
Added support for the latest Intel and AMD processors
In Red Hat Enterprise Linux 6.3, libvirt
has been updated to add support for the latest Intel Core i3, i5, i7
and other Intel processors, and family 15h microarchitecture AMD
processors. With this update, libvirt now utilizes the new features these processors include.
Chapter 8. Clustering and High Availability
Administrative UI enhancements
Luci, the web-based administrative UI for configuring clusters, has been updated to include the following:
A confirmation dialog box appears when removing a clustered service.
The UI includes an improved restart icon.
The Add a child resource button has been simplified.
An option to enable debugging from the UI has been added.
Automatic timeout of inactive luci authenticated sessions
As of Red Hat Enterprise Linux 6.3, luci authenticated sessions automatically time out after 15 minutes of inactivity. This period can be configured in the /etc/sysconfig/luci file by modifying the who.auth_tkt_timeout parameter.
New libqb package
The libqb package provides a library
with the primary purpose of providing high performance client server
reusable features, such as high performance logging, tracing,
inter-process communication, and polling. This package is introduced as a
dependency of the pacemaker package, and is considered a Technology Preview in Red Hat Enterprise Linux 6.3.
Pacemaker now uses libqb logging
Because of the newly added libqb dependency, pacemaker now uses its logging functionality to provide less verbosity while keeping the ability to debug and support pacemaker.
Utilizing CPG API for inter-node locking
Rgmanager includes a feature which enables it to utilize Corosync's
Closed Process Group (CPG) API for inter-node locking. This feature is
automatically enabled when Corosync's Redundant Ring Protocol (RRP)
feature is enabled. Corosync's RRP feature is considered fully
supported. However, when used with the rest of the High-Availability
Add-Ons, it is considered a Technology Preview.
Chapter 9. Storage
LVM support for (non-clustered) thinly-provisioned snapshots
A new implementation of LVM copy-on-write (cow) snapshots is
available in Red Hat Enterprise Linux 6.3 as a Technology Preview. The
main advantage of this implementation, compared to the previous
implementation of snapshots, is that it allows many virtual devices to
be stored on the same data volume. This implementation also provides
support for arbitrary depth of recursive snapshots (snapshots of
snapshots of snapshots …).
This feature is for use on a single-system. It is not available for multi-system access in cluster environments.
For more information, refer to documentation of the -s/--snapshot option in the lvcreate man page.
LVM support for (non-clustered) thinly-provisioned LVs
Logical Volumes (LVs) can now be thinly provisioned to manage a
storage pool of free space to be allocated to an arbitrary number of
devices when needed by applications. This allows creation of devices
that can be bound to a thinly provisioned pool for late allocation when
an application actually writes to the LV. The thinly-provisioned pool
can be expanded dynamically if and when needed for cost-effective
allocation of storage space. In Red Hat Enterprise Linux 6.3, this
feature is introduced as a Technology Preview. You must have the device-mapper-persistent-data package installed to try out this feature. For more information, refer to the lvcreate man page.
Dynamic aggregation of LVM metadata via lvmetad
Most LVM commands require an accurate view of the LVM metadata stored
on the disk devices on the system. With the current LVM design, if this
information is not available, LVM must scan all the physical disk
devices in the system. This requires a significant amount of I/O
operations in systems that have a large number of disks.
The purpose of the lvmetad daemon is
to eliminate the need for this scanning by dynamically aggregating
metadata information each time the status of a device changes. These
events are signaled to lvmetad by udev rules. If lvmetad is not running, LVM performs a scan as it normally would.
This feature is provided as a Technology Preview and is disabled by
default in Red Hat Enterprise Linux 6.3. To enable it, refer to the use_lvmetad parameter in the /etc/lvm/lvm.conf file, and enable the lvmetad daemon by configuring the lvm2-lvmetad init script.
Fiber Channel over Ethernet (FCoE) target mode fully supported
Fiber Channel over Ethernet (FCoE) target mode is fully supported in
Red Hat Enterprise Linux 6.3. This kernel feature is configurable via
the targetcli utility, supplied by the fcoe-target-utils package. FCoE is designed to be used on a network supporting Data Center Bridging (DCB). Further details are available in the dcbtool(8) and targetcli(8) man pages (provided by the lldpad and fcoe-target-utils packages, respectively).
LVM RAID fully supported with the exception of RAID logical volumes in HA-LVM
The expanded RAID support in LVM is now fully supported in Red Hat
Enterprise Linux 6.3. LVM is now capable of creating RAID 4/5/6 logical
volumes and supports mirroring of these logical volumes. The MD
(software RAID) modules provide the backend support for these new
Activating volumes in read-only mode
A new LVM configuration file parameter, activation/read_only_volume_list,
makes it possible to always activate particular volumes in read-only
mode, regardless of the actual permissions on the volumes concerned.
This parameter overrides the --permission rw option stored in the metadata.
Chapter 10. General Updates
Matahari packages deprecated
The Matahari agent framework (matahari-*)
packages are deprecated starting with the Red Hat Enterprise Linux 6.3
release. Focus for remote systems management has shifted towards the use
of the CIM infrastructure. This infrastructure relies on an already
existing standard which provides a greater degree of interoperability
for all users. It is strongly recommended that users discontinue the use
of the matahari packages and other packages which depend on the Matahari infrastructure (specifically, libvirt-qmf and fence-virtd-libvirt-qpid).
It is recommended that users uninstall Matahari from their systems to
remove any possibility of security issues being exposed.
Users who choose to continue to use the Matahari agents should note the following:
The matahari packages are not installed
by default starting with Red Hat Enterprise Linux 6.3 and are not
enabled by default to start on boot when they are installed. Manual
action is needed to both install and enable the matahari services.
The default configuration for qpid
(the transport agent used by Matahari) does not enable access control
lists (ACLs) or SSL. Without ACLs/SSL, the Matahari infrastructure is
not secure. Configuring Matahari without ACLs/SSL is not recommended and
may reduce your system's security.
agent is specifically designed to allow remote manipulation of services
(start, stop). Granting a user access to Matahari services is
equivalent to providing a remote user with root access. Using Matahari
agents should be treated as equivalent to providing remote root SSH
access to a host.
By default in Red Hat Enterprise Linux, the Matahari broker (qpidd running on port 49000)
does not require authentication. However, the Matahari broker is not
remotely accessible unless the firewall is disabled, or a rule is added
to make it accessible. Given the capabilities exposed by Matahari
agents, if Matahari is enabled, system administrators should be
extremely cautious with the options that affect remote access to
Note that Matahari will not be shipped in future releases of Red Hat
Enterprise Linux (including Red Hat Enterprise Linux 7), and may be
considered for formal removal in a future release of Red Hat Enterprise
Software Collections utilities
Red Hat Enterprise Linux 6.3 includes an scl-utils
package which provides a runtime utility and packaging macros for
packaging Software Collections. Software Collections allow users to
concurrently install multiple versions of the same RPM packages on the
system. Using the scl utility, users may enable specific versions of RPMs which are installed in the /opt directory. For more information on Software Collections, refer to the Software Collections Guide.
The openssl-ibmca package is now part of the IBM System z default installation
With Red Hat Enterprise Linux 6.3, the openssl-ibmca package is part of the System z default installation. This avoids the need for manual installation steps.
MySQL InnoDB plug-in
Red Hat Enterprise Linux 6.3 provides the MySQL InnoDB storage engine
as a plug-in for AMD64 and Intel 64 architectures. The plugin offers
additional features and better performance than the built-in InnoDB
Red Hat Enterprise Linux 6.3 introduces OpenJDK 7 as a Technology
Preview, as an alternative to the fully-supported OpenJDK 6.
New Java 7 packages
The java-1.7.0-oracle and java-1.7.0-ibm packages are now available in Red Hat Enterprise Linux 6.3.
Setting the NIS domain name via initscripts
The initscripts package has been updated to allow users to set the NIS domain name. This is done by configuring the NISDOMAIN parameter in the /etc/sysconfig/network file, or other relevant configuration files.
ACL support for logrotate
Previously, when certain groups were permitted to access all logs via
ACLs, these ACLs were removed when the logs were rotated. In Red Hat
Enterprise Linux 6.3, the logrotate utility supports ACLs, and logs that are rotated preserve any ACL settings.
The wacomcpl package deprecated
The wacomcpl package has been deprecated and has been removed from the package set. The wacomcpl
package provided graphical configuration of Wacom tablet settings. This
functionality is now integrated into the GNOME Control Center.
Updated NumPy package
The NumPy package which is designed to
manipulate large multi-dimensional arrays of arbitrary records has been
updated to version 1.4.1. This updated version includes these changes:
When operating on 0-d arrays, numpy.max and other functions accept only the following parameters: axis=0, axis=-1, and axis=None. Using out-of-bounds axes indicates a bug, for which NumPy now raises an error.
Specifying the axis > MAX_DIMS parameter is no longer allowed; NumPy now raises an error, instead of behaving the same as when axis=None was specified.
Rsyslog updated to major version 5
The rsyslog package has been upgraded to
major version 5. This upgrade introduces various enhancements and fixes
multiple bugs. The following are the most important changes:
The $HUPisRestart directive
has been removed and is no longer supported. Restart-type HUP processing
is therefore no longer available. Now, when the SIGHUP signal is
received, outputs (log files in most cases) are only re-opened to
support log rotation.
The format of the spool files (for example, disk-assisted queues)
has changed. In order to switch to the new format, drain the spool
files, for example, by shutting down rsyslogd. Then, proceed with the Rsyslog upgrade, and start rsyslogd again. Once upgraded, the new format is automatically used.
When the rsyslogd daemon was running in the debug mode (using the -d option), it ran in the foreground. This has been fixed and the daemon is now forked and runs in the background, as is expected.