I'm running servers on the Rackspace Cloud -- the first-generation one, not the next-generation Open Stack one. I believe it's running Xen for the hypervisor.
I use the stock images from Rackspace. I primarily use 10.04 servers, but I've also been rolling out new servers with 12.04.
My problem is that I want to keep the kernel up-to-date. I can apt-get dist-upgrade for new kernels, and the installation works fine. However, when I reboot, the server doesn't come back up.
My guess is that there's some custom hackery around the grub configuration that makes the stock kernels work, but upgraded kernels fail.
Has anyone had a similar problem on the Rackspace Cloud? What's the smallest modification I need to make grub boot a new kernel?