RHBA-2010:0238 - Bug Fix Advisory

Topic

An updated ktune package that fixes a clock drift bug in Red Hat Enterprise
Linux guests and adds support for the ktune.d directory is now available.

Description

The ktune package includes settings for server performance-tuning.

This updated ktune package fixes the following bug:

• when running a Red Hat Enterprise Linux KVM guest under heavy load, the

guest's system clock had the tendency to drift by an amount correlated with
the system load. This ktune update provides an interactive Bourne shell
script, fix_clock_drift.sh, which, when run as with root privileges,
inspects various system parameters to determine if the guest on which it is
run is susceptible to clock drift under load and, if so, creates a new
"grub.conf.kvm" file in the /boot/grub/ directory. This file contains a
kernel boot line with additional kernel parameters that allow the kernel to
account for and prevent significant clock drift on the KVM guest.
(BZ#516652)

Note: the ntpd service must be running on the KVM guest for the clock drift
to be corrected.

Important: this script does not replace the existing grub.conf file. If
running fix_clock_drift.sh creates the file "grub.conf.kvm" the system
administrator must set the new file up manually as follows: back up the
guest's current "grub.conf" file; inspect "grub.conf.kvm" and ensure it is
identical to "grub.conf" with the exception of the additional boot line
parameters; re-name "grub.conf.kvm" to "grub.conf"; reboot the guest.

This update also adds the following enhancement:

• support for ktune.d directory has been added to load additional sysctl

profiles. Each profile could also provide a script for settings which can
not be done with sysctl. The script will get an option which will be start
or stop according to the ktune service command used for ktune. (BZ#496940)

Users of Red Hat Enterprise Linux KVM guests, especially those affected by
significant clock drift, are advised to upgrade to this updated package,
which resolves this issue and adds this enhancement.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/docs/DOC-11259

Affected Products

• Red Hat Enterprise Linux Server 5 x86_64
• Red Hat Enterprise Linux Server 5 ia64
• Red Hat Enterprise Linux Server 5 i386
• Red Hat Enterprise Linux for IBM z Systems 5 s390x
• Red Hat Enterprise Linux for Power, big endian 5 ppc
• Red Hat Enterprise Linux Server from RHUI 5 x86_64
• Red Hat Enterprise Linux Server from RHUI 5 i386

Fixes

• BZ - 516652 - need script to set kernel parameters that fix clock drift

CVEs

(none)

References

(none)