I could really use some advice. I started a new instance on EC2 using Amazon's AMI and during the deployment process I selected a Kernel ID of "Use Default". I then configured my server the way that I wanted to and took a snapshot of it. I then created my own AMI to create new servers with. When I try and create a new server with this AMI the server fails to start and I get the error: EXT3-fs: sda1: couldn't mount because of unsupported optional features (240).

Which appears to happen because I am selecting a kernel id of "Use default" again when building my second server. I have read that in order for this to work I need to choose the same kernel id that was used in my original server. I have deleted my original server and don't know what it was using.

What is the best process to follow in order to not have these issues? Should I choose "Use Default" for my original server? How do you know which kernel it selected? Then should I just document this and always specify this during the deployment of my next servers using my custom AMI? OR should I choose a custom kernel id during the initial build and always use this one moving ahead hoping Amazon never retires it?
Thanks for any advice!


It's probably because the kernel in the AMI supports ext2 and ext3 by default, but not ext4. I would try creating a new instance and mounting the volume that won't boot. I'll bet it's ext4. In that case, probably the fastest way to get back up-and-running is to copy data off of that volume and onto a new one.

I always use Amazon Linux instances, and I always choose the default kernel. I haven't gotten bitten by this, but you have me thinking about when I should document the kernel ID. Hope this helps.

  • Thanks for the response, its actually ext3 and ext4. I did not choose these filesystem types, they came with the Amazon core AMI that I used, which is the frustrating part. Do you know how to see what kernel is being used after my first instance has been deployed? – roacha Nov 9 '12 at 21:02

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