EC2 small to micro instance downgrade problems.

Question

Have a few applications where EC2 small instances are, well, too large. So the announcement of micro instances is just what the doctor ordered.

I'd like to take a small instance's EBS volume, detach it, and pair it up with a micro instance. At some point it might be great to go the other way and upsize a micro instance to a small or beyond.

For this failed experiment I tried:

1. Creating a new small instance with the Alestic Ubuntu 10.04 32 bit AMI (ami-1234de7b). Boots like a charm.
2. Power down my freshly minted micro instance, detach the volume that was created for me in the previous step.
3. Attach the small instance's volume to the micro instance.
4. Power up.
5. Nada.

What's odd is there is no console log output until I power down. Then I see it all.

[    0.000000] Reserving virtual address space above 0xf5800000
[    0.000000] Initializing cgroup subsys cpuset
[    0.000000] Initializing cgroup subsys cpu
...
[    1.221261] VFS: Mounted root (ext3 filesystem) readonly on device 8:1.
[    1.221261] VFS: Mounted root (ext3 filesystem) readonly on device 8:1.
[    1.222164] devtmpfs: mounted
[    1.222202] Freeing unused kernel memory: 216k freed
[    1.223409] Write protecting the kernel text: 4328k
[    1.223760] Write protecting the kernel read-only data: 1336k
init: console-setup main process (63) terminated with status 1
%Ginit: plymouth main process (45) killed by SEGV signal
init: plymouth-splash main process (196) terminated with status 2
cloud-init running: Thu, 09 Sep 2010 17:37:54 +0000. up 2.61 seconds
mountall: Disconnected from Plymouth
init: hwclock-save main process (291) terminated with status 1
Checking for running unattended-upgrades:  * Asking all remaining processes to terminate...       
[80G 
[74G[ OK ]
 * All processes ended within 1 seconds....       
[80G 
[74G[ OK ]
 * Deconfiguring network interfaces...       
[80G 
[74G[ OK ]
 * Deactivating swap...       
[80G 
[74G[ OK ]
 * Unmounting local filesystems...       
[80G 
[74G[ OK ]
 * Will now halt
[  185.599636] System halted.

This method of swapping has worked well between same sized instanced in the past and it's my first attempt at doing this between different sizes. Is this just not possible or am I missing something fundamental in my EC2 knowledge?

Answer 1

I don't see a problem on your side. This could be a problem in Amazon's infrastructure.

Answer 2

Even though this will probably be migrated to Server Fault, I ran into the exact same problem with this instance earlier today.

It appears that this image assumes that there will be ephemeral storage present, when there is none on the micro instances. To work around this, comment out the following line in /etc/fstab:

/dev/sda2   /mnt    auto    defaults,comment=cloudconfig    0   0

This should prevent the instance from hanging on startup, or at least it did for me with ami-1234de7b.

Answer 3

I created a new micro instance using alestic ami's (ami-2c354b7e). I was able to login to the system normally the first time. But once I reboot the system, I was not able to login again.

commenting the line indicated above worked for me. "/dev/sda2 /mnt auto defaults,comment=cloudconfig 0 0"

Answer 4

Commenting the line out doesn't fix it fully. If you reboot, it will write the same line back in. You need to:

$ l="deb http://archive.ubuntu.com/ubuntu lucid-proposed main"
$ echo "$l" | sudo tee -a /etc/apt/sources.list
$ sudo apt-get update && sudo apt-get install cloud-init
$ dpkg-query --show cloud-init

I'm assuming this will be fixed in the official Ubuntu release soon and you won't have to do this, but for now...

Source: https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/634102

Also, we have a couple images based off the official Ubuntu AMI's that work on Micro's: http://blog.simpledeployr.com/2010/09/new-ruby-amis-with-latest-ubuntu-lucid.html