The Boot Loader Program

The boot loader controls how the virtualization software boots and runs. You can modify the boot loader properties by using YaST or by directly editing the boot loader configuration file.

The YaST boot loader program is located at YaST+System+Boot Loader. The Boot Loader Settings screen lists the sections that appear as options on the boot menu. From this screen, you can change the boot loader so it auto-selects the virtual machine host option when booting.

Figure 5.3. Boot Loader Settings

Select the Xen section, then click Edit to manage the way the boot loader and Xen function.

Figure 5.4. Boot Loader Settings: Section Management

You can use the Boot Loader program to specify functionality, such as:

You can customize your virtualization environment by editing the /boot/grub/menu.lst file.

If the Xen option does not appear on the GRUB boot menu, you can compare your updated GRUB boot loader file with the examples below to confirm that it was updated correctly.

The first example shows a typical GRUB boot loader file updated to load the kernel that supports virtualization software. The second example shows a GRUB boot loader file that loads the PAE-enabled virtualization kernel.

title XEN
 root (hd0,5)
 kernel /boot/xen.gz hyper_parameters
 module /boot/vmlinuz-xen kernel_parameters
 module /boot/initrd-xen

title XEN
 root (hd0,5)
 kernel /boot/xen-pae.gz hyper_parameters
 module /boot/vmlinuz-xenpae kernel_parameters
 module /boot/initrd-xenpae

The title line defines sections in the boot loader file. Do not change this line, because YaST looks for the word XEN to verify that packages are installed.

The root line specifies which partition holds the boot partition and /boot directory. Replace hd0,5 with the correct partition. For example, if the drive designated as hda1 holds the /boot directory, the entry would be hd0,0.

The kernel line specifies the directory and filename of the hypervisor. Replace hyper_parameters with the parameters to pass to the hypervisor. A common parameter is dom0_mem=<amount_of_memory>, which specifies how much memory to allocate to Domain0. The amount of memory is specified in KB, or you can specify the units with a K, M, or G suffix, for example 128M. If the amount is not specified, the Domain0 takes the maximum possible memory for its operations.

For more information about hypervisor parameters, see /usr/share/doc/packages/xen/pdf/user.pdf section “Xen Boot Options” after installing the package xen-doc-pdf.

The first module line specifies the directory and filename of the Linux kernel to load. Replace kernel_parameters with the parameters to pass to the kernel. These parameters are the same parameters as those that can be passed to a standard Linux kernel on physical computer hardware.

The second module line specifies the directory and filename of the RAM disk used to boot the virtual machine host.

To set the GRUB boot loader to automatically boot the Xen virtualization software, change the default entry from 0, which means the first title entry, to the number that corresponds to the title XEN entry. In the example file, Xen is the second title line, so to specify it, you would change the value of default from 0 to 1.