Chapter 2. Setting Up a Virtual Machine Host / 2.4. Starting the Virtual Machine Host
	2.3. Managing Domain 0 Memory		Chapter 3. Setting Up Virtual Machines

Starting the Virtual Machine Host

If virtualization software is correctly installed, the computer boots to display the GRUB boot loader with a Xen option on the menu. Select this option to start the virtual machine host.

Xen and Kdump

	Xen and Kdump
In Xen, the hypervisor manages the memory resource. If you need to reserve system memory for a recovery kernel in Domain0, this memory has to be reserved by the hypervisor. Thus, it is necessary to add the parameter `crashkernel=size@offset` to the `kernel` line instead of using the line with the other boot options. For more about Kdump, see also http://www.novell.com/rc/docrepository/public/37/basedocument.2007-09-13.2960758124/4622069_f_en.pdf.

In Xen, the hypervisor manages the memory resource. If you need to reserve system memory for a recovery kernel in Domain0, this memory has to be reserved by the hypervisor. Thus, it is necessary to add the parameter crashkernel=size@offset to the kernel line instead of using the line with the other boot options. For more about Kdump, see also http://www.novell.com/rc/docrepository/public/37/basedocument.2007-09-13.2960758124/4622069_f_en.pdf.

If the Xen option is not on the GRUB menu, review the steps for installation and verify that the GRUB boot loader has been updated. If the installation has been done without selecting the Xen pattern, run the YaST Software Management, select the filter Patterns and choose Xen Virtual Machine Host Server for installation.

After booting the hypervisor, the Domain0 virtual machine starts and displays its graphical desktop environment. If you did not install a graphical desktop, the command line environment appears.

Before starting to install virtual guests, make sure that the system time is correct. To do this, configure NTP (Network Time Protocol) on the controlling domain:

In YaST select Network Services+NTP Configuration.
Select the option to automatically start the NTP daemon during boot. Provide the IP address of an existing NTP time server, then click Finish.

Time Services on Virtual Guests

	Time Services on Virtual Guests
Hardware clocks commonly are not very precise. All modern operating systems try to correct the system time compared to the hardware time by means of an additional time source. To get the correct time on all VM Guest systems, also activate the network time services on each respective guest or make sure that the guest uses the system time of the host. For more about `Independend Wallclocks` in SUSE Linux Enterprise Server see Section 6.3.4, “Virtual Machine Clock Settings”.

Hardware clocks commonly are not very precise. All modern operating systems try to correct the system time compared to the hardware time by means of an additional time source. To get the correct time on all VM Guest systems, also activate the network time services on each respective guest or make sure that the guest uses the system time of the host. For more about Independend Wallclocks in SUSE Linux Enterprise Server see Section 6.3.4, “Virtual Machine Clock Settings”.

For more information about managing virtual machines, see Chapter 4, Managing a Virtualization Environment.