Comment 0 for bug 364916

When an Ubuntu AMI is being run as an instance in Eucalyptus, using an EBS volume requires that the acpiphp module be loaded. Unfortunately, the kernel and modules are not installed in the root filesystem, which mean the acpiphp module is not available to be loaded in the first place.

I can think of two ways to work-around the problem:

- Install linux-image-$(uname -r) inside the instance, and load acpiphp in /etc/modules or somesuch. The drawback is that doing this have a pretty important footprint in term of disk (115 MB) and network download.

- Upload to the cloud an initramfs image that have the acpiphp module in it. The drawback is that doing so needs to be documented, and it make creating/uploading/registering the image more complicated, and non-orthogonal with creating an image for EC2.

Having the kernel built with CONFIG_HOTPLUG_PCI_ACPI=y would also resolve the problem nicely. Or maybe there would be a more elegant work-around, which I would love to hear about.

Just to clarify, this is not a problem on EC2, or when running as an instance on an Eucalyptus cloud that use the Xen hypervisor. This problem is specific to running Eucalyptus with KVM, which is the default on Ubuntu. In that case, EBS volumes show up as block devices attached through virtual SCSI controller being hot-plugged, and that is why we need to have the acpiphp module loaded (or a kernel compiled with CONFIG_HOTPLUG_PCI_ACPI=y) in the first place.