Kernels and RAM Disk FAQ

What are user selectable kernels?

Amazon EC2 provides user selectable kernels which enables you to select a kernel when bundling an AMI or launching an instance. User selectable kernels are useful for keeping your instances up to date with security fixes and updates, being able to use functionality provided by new distributions, and for using specialty applications that have unique timing requirements.

How do I find user selectable kernels?

Use ec2-describe-images -o amazon --filter "image-type=kernel". This lists all public kernels that are currently available.

What type of dependencies do kernels have?

Kernels are most likely to require a RAM disk that contains required drivers (e.g., Xen drivers, video drivers, and so on). If you launch a kernel without a required RAM disk, it will not work properly.

How do I know a kernel/AMI combination will work together?

If you are concerned about whether the kernel/image combination will work well together, Amazon provides several AMIs that have tested combinations that you can use as a starting point for your AMIs or AMIs that you can use as a foundation for a public AMIs. If you require a certified kernel/ AMI combination, you can find them as paid AMIs through organizations such as RedHat. For more information, see Paying for AMIs.

Can I use my own kernel?

Yes. For more information, see Enabling Your Own Linux Kernels.

How do I know which kernels are compatible with PVGRUB?

For a list of compatible PVGRUB kernels, see Compatible PV-GRUB Kernels. Some Linux distributions provide kernels that are not compatible with Amazon EC2. We are working with vendors to ensure that the most popular AMIs provide kernels that work with Amazon EC2, and we have tested a number of these AMIs and found them to be compatible with PVGRUB. Unfortunately, it is not possible to support every kernel that is or can be compiled. To avoid the situation in which a kernel does not work consistently or at all, we recommend that you use a known good kernel, select a non-PVGRUB AKI, or seek support from your AMI vendor.