26.2. Modifying /etc/grub.conf

26.2. Modifying /etc/grub.conf

This section describes how to safely and correctly change your /etc/grub.conf file to use the virtualization kernel. You must use the virtualization kernel for domain0 in order to successfully run the hypervisor. Copy your existing virtualized kernel entry make sure you copy all of the important lines or your system will panic upon boot (initrd will have a length of '0'). You need specify hypervisor specific values you have to add them to the xen line of your grub entry.

The output below is an example of a grub.conf entry from a Red Hat Virtualization system. The grub.conf on your system may vary. The important part in the example below is the section from the title line to the next new line.

#boot=/dev/sda
default=0
timeout=15
#splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console

title Red Hat Enterprise Linux Server (2.6.17-1.2519.4.21.el5xen)
	root (hd0,0)
	kernel /xen.gz-2.6.17-1.2519.4.21.el5 com1=115200,8n1
	module /vmlinuz-2.6.17-1.2519.4.21.el5xen ro root=/dev/VolGroup00/LogVol00
	module /initrd-2.6.17-1.2519.4.21.el5xen.img

An important point regarding editing grub.conf...

Your grub.conf could look very different if it has been manually edited before or copied from an example. Read Chapter 23, Configuring GRUB for more information on using virtualization and grub.

To set the amount of memory assigned to your host system at boot time to 256MB you need to append dom0_mem=256M to the xen line in your grub.conf. A modified version of the grub configuration file in the previous example:

#boot=/dev/sda
default=0
timeout=15
#splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console

title Red Hat Enterprise Linux Server (2.6.17-1.2519.4.21.el5xen)
	root (hd0,0)
	kernel /xen.gz-2.6.17-1.2519.4.21.el5 com1=115200,8n1 dom0_mem=256MB
	module /vmlinuz-2.6.17-1.2519.4.21.el5xen ro
	root=/dev/VolGroup00/LogVol00
	module /initrd-2.6.17-1.2519.4.21.el5xen.img

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