Creating Virtual Machines
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Xen Domain Memory
In our current configuration, the dom0 kernel takes up all the memory available
within the system on start up, and then assigns it out to the domUs as needed. When
we create guest domains in this chapter we need a way to provide memory for
each of the guest domains that we create. Xen provides a simple way to specify the
memory used by the dom0 kernel a parameter to the hypervisor on start up. Modify
the /boot/grub/menu.lst in your base system and add an additional parameter to
the kernel line specifying the amount of maximum memory that you want the dom0
kernel to use:
kernel /xen.gz noreboot dom0_mem=256M
On my system, I assigned a memory size of 256M to my dom0. If you are only going
to manage a Xen host and will not have any guest domains, you can go lower than
256M of memory, and may be able to get by with 96M of memory. However, if you
are using any guest domains, you will need to ensure that you have enough memory
available to be assigned to the guests as they start up. In this case you should set the
memory to at least 512M. When we create new guest domains in this chapter, we
will specify the maximum memory to be used by each of the guest domains in the
configuration file for the domain.
Pygrub
The normal way in Xen is to specify the kernel and initrd from within the config
file in dom0. This means that any time the kernel needs to be modified or changed,
you will need administrative privileges on dom0 host in order to modify it.
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