E.6 setting the guest’s clock, E.7 wallclock time skew problems, E.8 mouse pointer tracking problems – Oracle Audio Technologies E10898-02 User Manual
Page 101: Setting, Wallclock time skew, Setting the guest’s clock, Wallclock time skew problems, Mouse pointer tracking problems
Mouse Pointer Tracking Problems
E.6 Setting the Guest’s Clock
Paravirtualized guests may perform their own system clock management, for
example, using the NTPD (Network Time Protocol daemon), or the hypervisor may
perform system clock management for all guests.
You can set paravirtualized guests to manage their own system clocks by setting the
in the /etc/sysctl.conf file. For
"xen.independent_wallclock = 1"
If you want to set the hypervisor to manage paravirtualized guest system clocks, set
. Any attempts to set or modify the time in a
guest will fail.
You can temporarily override the setting in the /proc file. For example
"echo 1 > /proc/sys/xen/independent_wallclock"
E.7 Wallclock Time Skew Problems
Oracle VM Release 2.1.1 introduces the use of the
hardware virtualized guests. This parameter, when properly applied, can reduce or
even eliminate problems with wallclock time skew in most hardware virtualized
guests. Wallclock time skew problems do not occur in paravirtualized guests.
Since the application of the correct value of the
parameter can be
difficult to determine, you can pass the
switches to virt-install to select the best
value for the guest operating
system. When you use these virt-install parameters, the correct
automatically added to the guest configuration file. For example, to create an Oracle
Enterprise Linux 5 64-bit guest, add the following to the virt-install command-line:
# virt-install --hvm ... --os-type=linux --os-variant=el5_64 ...
For best results, additional parameters may be needed in the boot loader (grub.conf)
configuration file for certain operating system variants after the guest is installed.
Specifically, for optimal clock accuracy, Linux guest boot parameters should be
specified to ensure that the pit clock source is utilized. Adding
for most guests will result in the selection of pit as the clock source for the
guest. Published templates for Oracle VM will include these additional parameters.
Proper maintenance of virtual time can be tricky. The various parameters provide
tuning for virtual time management and supplement, but do not replace, the need for
an ntp time service running within guest. Ensure that the
service is running and
that the /etc/ntpd.conf configuration file is pointing to valid time servers.
E.8 Mouse Pointer Tracking Problems
If your mouse pointer fails to track your cursor in a VNC Viewer session in a hardware
virtualized guest, add the following to the Oracle VM Server configuration file located
at /etc/xen/xend-config.sxp to force the device model to use absolute (tablet)
This setting does not apply to hardware virtualized guests.