This section describes some problems you may encounter when using Oracle VM Server, and explains how to resolve them.
If you need to contact Oracle Support Services, you will be asked to supply the log files mentioned in this section. You may also be required to provide the exact version of each Oracle VM component. To find the version of Oracle VM Manager, click the Help menu, then About. To find the version of Oracle VM Server and Oracle VM Agent, see Section 6.9.15, “Viewing Oracle VM Server Operating System Information and Control Domains”.
If virtual machine creation fails, check the Oracle VM Server log files and use the command-line tools to help you find the cause of a problem. There are a number of useful command-line tools, important directories, and log files that you should check when troubleshooting problems with Oracle VM Server. This section discusses:
Oracle VM Server directories
Oracle VM Server log files
Oracle VM Server command-line tools
The important Oracle VM Server directories you should check when troubleshooting problems with Oracle VM Server are listed in Table B.2, “Oracle VM Server directories”
Table B.2. Oracle VM Server directories
Directory | Purpose |
---|---|
/etc/xen | Contains Oracle VM Server configuration files for the Oracle VM Server daemon and virtualized guests. |
/etc/xen/scripts | Contains networking related scripts. |
/var/log | Contains the Oracle VM Agent log file, ovs-agent.log. Contains the ovmwatch.log, which logs virtual machine life cycle events. Contains the ovm-consoled.log, which logs remote VNC console access, and all communication with Oracle VM Manager. |
/var/log/xen | Contains Oracle VM Server log files. |
/var/log/messages | Contains Oracle VM Server messages. |
The Oracle VM Server log files you should check when troubleshooting problems with Oracle VM Server are listed in Table B.3, “Oracle VM Server log files”
Table B.3. Oracle VM Server log files
Log File | Purpose |
---|---|
xend.log |
Contains a log of all the actions of the Oracle VM Server
daemon. Actions are normal or error conditions. This
log contains the same information as output using
the |
xend-debug.log | Contains more detailed logs of the actions of the Oracle VM Server daemon. This file is located in the /var/log/xen directory. |
xen-hotplug.log | Contains a log of hotplug events. Hotplug events are logged if a device or network script does not start up or become available. This file is located in the /var/log/xen directory. |
qemu-dm.pid.log | Contains a log for each hardware virtualized guest. This log is created by the quemu-dm process. Use the ps command to find the pid (process identifier) and replace this in the file name. This file is located in the /var/log/xen directory. |
ovs-agent.log | Contains a log for Oracle VM Agent. This file is located in the /var/log/ directory. |
osc.log | Contains a log for Oracle VM Storage Connect Plug-ins. This file is located in the /var/log/ directory. |
ovm-consoled.log | Contains a log for the Oracle VM virtual machine console. This file is located in the /var/log/ directory. |
ovmwatch.log | Contains a log for the Oracle VM watch daemon. This file is located in the /var/log/ directory. |
The Oracle VM Server command-line tools you should use when troubleshooting problems with Oracle VM Server are listed in Table B.4, “Oracle VM Server command-line tools”.
Table B.4. Oracle VM Server command-line tools
Command-Line Tool | Purpose |
---|---|
xentop | Displays real-time information about Oracle VM Server and domains. |
xm dmesg | Displays log information on the hypervisor. |
xm log | Displays log information of the Oracle VM Server daemon. |
A further set of Oracle VM command line utilities are available for download, separate to the Oracle VM Server in-built utilities. These Oracle VM utilities are a collection of command line scripts that allow you to perform a set of basic management tasks on Oracle VM Servers and virtual machines in an Oracle VM environment. These utilities are particularly useful to administrators who need to execute certain operations quickly and/or repeatedly. Using the command line scripts makes these tasks quicker and easier to perform. See the Oracle VM Utilities Guide for more information on these utilities.
It is recommended that you install Oracle VM Server on a computer with a static IP address. If your computers uses DHCP you should configure your DHCP server to assign static DHCP addresses. This makes sure your host always receives the same IP address. The behavior of the Oracle VM Server host is undefined if used in an environment where your IP address may change due to DHCP lease expiry.
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
xen.independent_wallclock
parameter to
1
in the /etc/sysctl.conf file. For example
"xen.independent_wallclock = 1"
If you want to set the hypervisor to manage paravirtualized
guest system clocks, set
xen.independent_wallclock
to
0
. 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"
This setting does not apply to hardware virtualized guests.
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 clock=pit nohpet nopmtimer
for most guests will result in the selection of
pit as the clock source for the guest.
Published templates for Oracle VM 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 ntpd
service is running and
that the /etc/ntpd.conf configuration file is pointing to valid
time servers.
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) coordinates:
usbdevice='tablet'
Restart the Oracle VM Server for the changes to take effect. You may need to do this for each Oracle VM Server in the server pool.
When running hardware virtualized guests, the QEMU process (qemu-dm) may have its memory usage grow substantially, especially under heavy I/O loads. This may cause the hardware virtualized guest to stop as it runs out of memory. If the guest is stopped, increase the memory allocation for dom0, for example from 512MB to 768MB.
Some devices, such as sound cards, may not work as expected in hardware virtualized guests. In a hardware virtualized guest, a device that requires physical memory addresses instead uses virtualized memory addresses, so incorrect memory location values may be set. This is because DMA (Direct Memory Access) is virtualized in hardware virtualized guests.
Hardware virtualized guest operating systems expect to be loaded in memory starting somewhere around address 0 and upwards. This is only possible for the first hardware virtualized guest loaded. Oracle VM Server virtualizes the memory address to be 0 to the size of allocated memory, but the guest operating system is actually loaded at another memory location. The difference is fixed up in the shadow page table, but the operating system is unaware of this.
For example, a sound is loaded into memory in a hardware virtualized guest running Windows at an address of 100MB may produce garbage through the sound card, instead of the intended audio. This is because the sound is actually loaded at 100MB plus 256MB. The sound card receives the address of 100MB, but it is actually at 256MB.
An IOMMU (Input/Output Memory Management Unit) in the computer's memory management unit would remove this problem as it would take care of mapping virtual addresses to physical addresses, and enable hardware virtualized guests direct access to the hardware.
Oracle VM Server blocks NFS access from any external computer (or guest) by default. This may cause problems when trying to create a guest using an NFS connection. To resolve this, disable the firewall with the following command:
# service iptables stop
You cannot migrate virtual machines on computers with hardware that is not identical. To migrate a virtual machines, you must have hardware that is the same make and model and the CPU must be in the same CPU family. You must also have the same Oracle VM Server release number.