I have a long running goal that I'm trying to reach with all these pv-grub for EC2 posts. That goal is to find the smallest/tightest usable node that can be created for EC2. The next step in that path requires a custom Linux kernel. What follows is how to build the latest Linux kernel so that it works on EC2 using pv-grub.
It is important to have a recent kernel since most of what is needed to get a kernel to work on EC2 is now incorporated into the source. These instructions assume the latest kernel is 126.96.36.199 and I've used them with 2.6.35 as well but keep that in mind since the one patch that is required could eventually be merged in. Before getting started it may help to read over how to compile the Linux kernel normally and then my post on running CentOS 5.5 on EC2 using pv-grub.
Amazon recently introduced the ability to boot a custom kernel using pv-grub on EC2. This opens the door for all kinds of interesting ideas that I've been thinking about for a while, like seeing if I can boot right into a web server and skip all that extra junk that comes with Linux distributions, but that is just me. The main door it is going to open for most people interested in EC2 will be the ability to upgrade the kernel that comes with their distribution. That brings us to how to install Cent OS 5.5 on EC2 and use the kernel that is part of the distribution.
For those who might just be interested in booting a custom kernel using EC2 pv-grub I will try to produce a few more posts with more details on that but for now here are the main things to know:
- The pv-grup kernels named with hd00 will look on the first partition of the registered device in the /boot/boot/grub directory for a menu.lst file. Use this type of kernel if you create want to use a partitioned disk.
- The pv-grup kernels named with hd0 will look on the registered device in the /boot/grub directory for a menu.lst file. Use this type of kernel if you don't have a partition on your disk.
- You won't get anything meaningful back from the boot attempt if your grub menu.lst file is in the wrong place or is not valid. See the end of the post for what a pv-grub error message looks like and some tips on what to do if you see it.
- The kernel you use does matter but the current mainline Linux kernel (2.6.35) contains everything you need except for a small change to turn off XSAVE. The main thing to know is that not every distribution may have made the change needed to work on EC2.
- I have tried non-Linux kernels to no avail. See the end of the post for a little more information.
I've been using S3 to store semi-transient information like log files from EC2 nodes in the past but recently decided to give Amazon's Elastic Block Store (EBS) a try instead. I quickly realized a downside to using EBS in that there is no mechanism for auto-attach and mounting volumes when an AMI is launched. This is probably something Amazon will fix at some point and allow you to launch a given AMI with an attached EBS volume but until then you need some way of doing it yourself. The following is a simple way of using ruby to make it happen.