i try to use a older vmdk image on KVM it seems to work on a debian kvm box but not on a CentOS 6 box the kvm on CentOS says no bootable device but on debian it boots fine
Have you specified the image type? I have experienced virt-manager not recognizing the image type (raw|qcow2) – specifying it solves the boot problem.
With your CentOS device, have you tried reinstalling grub?
That’s right. Make sure the disk is the CentOS install you have..
Boot into the CentOS 6 DVD and enter into rescue mode then chroot into your install, reinstall grub.
I use cli not virt-manager
Times like this, it might pay to use virt-manager. Just SSH -X
root@$host – assuming you have X forwarding enabled in your SSH config.