Given that it's impossible to "aptitude update" your way to a new kernel on an Amazon EC2 instance, I was wondering if it ever makes sense to apply kernel updates. My guess is no, and that I should have apt ignore all kernel updates (using the "aptitude hold" command or similar). Does anyone have any thoughts on this?
SnapOverflow
You're right that there's no point in installing them on a running instance. However, you should make sure that you are still notified when there are updates, install them in your AMI, and reboot your instances when possible. This is especially important for patching kernel-level vulnerabilities.
Since the release of the Ubuntu 10.04 LTS images that use the pv-grub kernel, you actually can "aptitude update" your way to a new kernel on an Amazon EC2 instance.