I have installed Xen 3.1.2 perfectly, and it's running fine. However since that version is way outdated I just updated it to 4.1.2 by adding the gitco repository and then yum update. It installed fine, modified my grub.conf to reflect the changes but then on a reboot, it simply doesn't come back online (I can't see what's going on, as it's a rented dedicated server).

What are my options? Booting into rescue mode and using the older kernel works fine, it will come back up. But once I use the xen.gz-4.1.2kernel, it won't come back up anymore and I need to use the rescue image..

My /boot/grub/grub.confis as follows:

title CentOS (2.6.18-308.1.1.el5xen)
        root (hd0,1)
        #kernel /xen.gz-2.6.18-308.1.1.el5 dom0_mem=1024M
        kernel /xen.gz-4.1.2
        module /vmlinuz-2.6.18-308.1.1.el5xen ro root=/dev/md1
        module /initrd-2.6.18-308.1.1.el5xen.img

When I uncomment the 3.1.2 kernel, it works fine, but booting with the 4.1.2 kernel fails and I have no idea what's going on. Hence my question: what are my options?

  • Do you have any console output or any diagnostic information about the boot sequence you can provide? – jonodlo Mar 31 '12 at 10:59
  • @jonodlo No, I just enter reboot, the system is rebooting and then I just wait till it comes back online. I can't see what's going on since I have no access to the physical server and no KVM either :-( – Devator Mar 31 '12 at 11:10
  • I could be wrong, but generally you would want to have the updated ramdisk/initrd in boot loader section. That and it is general practice to have a separate boot loader section for a new kernel. – Rilindo Mar 31 '12 at 12:49

You should also build a custom kernel, the one packaged by redhat is supposed to work with the xen hypervisor packaged with it. That's a lot of work!

Edit: You are right this should work, but xen 4 seems to use pv_ops by default, which available only from 2.6.32 kernels. The question is, is your Xen4 build accepting non-pv_ops kernels?

Several posts on the subject state the following:

if you're using RHEL5 or CentOS5 as a dom0 (ie. you have old udev version), make sure you enable the following options aswell:


This should give you a working xen for the redhat 2.6.18-xen kernels.

  • Why should I need to build my custom kernel? The gitco repository worked fine for updating 3.1.2 to 3.4.3. – Devator Mar 31 '12 at 11:10

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