Installation guide

options loop max_loop=64
This example uses 64 but you can specify another number to set the maximum loop value. You may
also have to implement loop device backed guests on your system. To employ loop device backed
guests for a para-virtualized guest, use the phy: block device or tap:aio commands. To
employ loop device backed guests for a full virtualized system, use the phy: device or file:
file commands.
36.5. Failed domain creat ion caused by a memory short age
This may cause a domain to fail to start. The reason for this is there is not enough memory available
or dom0 has not ballooned down enough to provide space for a recently created or started guest. In
your /var/log/xen/xend.log, an example error message indicating this has occurred:
[2006-11-21 20:33:31 xend 3198] DEBUG (balloon:133) Balloon: 558432 KiB free;
0 to scrub; need 1048576; retries: 20.
[2006-11-21 20:33:52 xend.XendDomainInfo 3198] ERROR (XendDomainInfo:202) Domain
construction failed
You can verify the amount of memory currently used by dom0 with the command “ xm list Domain-
0” . If dom0 is not ballooned down you can use the command “ xm mem-set Domain-0
NewMemSize” where NewMemSize should be a smaller value.
36.6. Wrong kernel image error
Para-virtualized guests cannot use the kernel-xen kernel. Use only the standard kernel for para-
virtualized guests.
Attempting to boot any kernel other than the Xen kernel as a para-virtualized guest results in the
following error message:
# xm create testVM
Using config file "./testVM".
Going to boot Red Hat Enterprise Linux Server (2.6.18-1.2839.el5)
kernel: /vmlinuz-2.6.18-1.2839.el5
initrd: /initrd-2.6.18-1.2839.el5.img
Error: (22, 'Invalid argument')
In the above error you can see that the kernel line shows that the system is trying to boot a non
kernel-xen kernel. The correct entry in the example is ” kernel: /vmlinuz-2.6.18-
1.2839.el5xen” .
The solution is to verify you have indeed installed a kernel-xen in your guest and it is the default
kernel to boot in your /etc/grub.conf configuration file.
If you have kernel-xen installed in your guest you can start your guest:
xm create -c GuestName
Where GuestName is the name of the guest. The previous command will present you with the G R UB
boot loader screen and allow you to select the kernel to boot. You will have to choose the kernel-xen
kernel to boot. Once the guest has completed the boot process you can log into the guest and edit
/etc/grub.conf to change the default boot kernel to your kernel-xen. Change the line
Red Hat En t erp rise Lin ux 5 Virt ualizat ion Guid e
34 4