How does an Amazon EC2 instance select its kernel?

Question

I have an Amazon EC2 instance using the Amazon-supplied Fedora 8 64-bit AMI, which I would like to upgrade to Fedora 10.

I tried doing this by running "yum update" to upgrade the kernel and all packages. This seemed to work fine and I see that I now have the fc10 kernel installed, and all of my installed packages have also been updated to the Fedora 10 versions.

However, I also noticed that the fc8 kernel is still installed, and when I reboot my image it comes back running the fc8 kernel, not the fc10 kernel (I'm inferring this from the output of "uname -a").

Are there some additional steps I need to take to get my image to boot under the fc10 kernel, or is this even possible? The Amazon documentation didn't turn up anything useful for me.

Answer 1

You can create your own AMI however you need to use the Amazon-supplied kernels. The newest they provide is 2.6.21. I have a listing of the FC (Fedora Core) kernels that I use for CentOS instances. I'm pretty sure they work fine with Ubuntu as well.

You'll want to bake these into your AMI once you register it using ec2-register. They can be modified at the time you start an instance but I favour having the right AKI (kernel) and ARI (ramdisk) to start with. Adding support for the ephemeral disks is useful as well. You're paying for the extra storage with larger instances, you might as well use it. My magic incantation for ec2-register:

ec2-register --snapshot snap-12345678 -K pk-XXXXXXXXXXX.pem -C cert-XXXXXXXXXXX.pem \

--description "EBS CentOS 5.5 i386" --name "base-image-i386-4" --architecture i386 \

--root-device-name /dev/sda1 -b /dev/sdb=ephemeral0 -b /dev/sdc=ephemeral1 \

-b /dev/sdd=ephemeral2 -b /dev/sde=ephemeral3 --region us-east-1 \

--kernel aki-6eaa4907 --ramdisk ari-e7dc3c8e

You can change the region, snapshot ID, description, name, arch, etc.

Also, remember the kernels & ramdisks are region-specific. I can't remember where I got this list but I had trouble finding it. Hope it helps someone out.

2.6.21 kernels are available as:

US Region:

32-bit:

* aki-6eaa4907

* ari-e7dc3c8e

* ami-48aa4921

64-bit:

* aki-a3d737ca

* ari-4fdf3f26

* ami-f61dfd9f

EU Region:

32-bit:

* aki-02486376

* ari-aa6348de

* ami-0a48637e

64-bit:

* aki-f2634886

* ari-a06348d4

* ami-927a51e6

AP Region:

64-bit:

* aki-07f58a55

* ari-27f58a75

* ami-ddf58a8f

32 -bit

* aki-01f58a53

* ari-25f58a77

* ami-c3f58a91