Create a bootable EBS AMI from a running instance

A quick set of notes on how to create a bootable EBS snapshot from a running EC2 instance - for example, an instance that has been started from an S3 backed AMI.

We've had to do this a few times over the last few months - for the benefit of others, we've outlined how we currently do it - this is based on a number of articles that were surfacing at the time of our research, but I don't have the links to hand. If there's a better way out there feel free to jump in!

Create an EBS volume (if converting from an S3 backed AMI then create it as 10Gb in size)
Attach the EBS volume to your running instance
Stop running services that may be locking files, etc, such as MySQL

At this point, you're ready to copy the contents of your root drive onto the EBS volume. A couple of additional points here - it makes sense to stop any services possible to make the transfer as clean as possible. One of our readers has suggested an alternative approach to dd in the comments - i've included it here as an option for completeness.

Option 1: dd

Copy the root drive to the EBS volume - dd bs=65536 if=SOURCE of=TARGET. Replace SOURCE with the boot volume, e.g. /dev/sda1 and TARGET with the EBS volume, e.g. /dev/sdj
fsck TARGET
mkdir /migrate
mount TARGET /migrate

Option 2: rsync

I suspect with this route you'd need to exclude any directories used for mounting other volumes, otherwise your rsync will run out of space on the target device.

mkfs.ext3 TARGET
mount TARGET /migrate
rsync -ax --progress / /migrate
rm -rf /migrate/migrate

And then continue..

At this point, you can make any necessary modifications to the fstab to allow your EBS based AMI to boot - the file can be found in /migrate/etc/fstab

umount TARGET

Create a snapshot of the EBS volume

Register the snapshot as an AMI by running ec2-register -n NAME --architecture ARCH --block-device-mapping /dev/sda1=SNAPSHOT:SIZE:false. There are a number of options here - some of which you can set when starting the instance if you prefer. NAME is the name of the AMI, ARCH is the architecture (i386 or x86_64). The block device mapping paramaters set the EBS snapshot to use as the boot device, the second parameter sets the size to 15Gb and final parameter sets the delete-on-termination attribute to false.

Run an instance based on the newly registered AMI - if you've set the EBS volume size to anything greater then 10Gb then expand the filesystem to the size of the device.

More details, as usual, can be found in the command line reference.

10 comments

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Comment on Create a bootable EBS AMI from a running instance by Chris Anderton

May 11th, 2010 @ 10:52 – permalink

I accidentally deleted a comment asking for an example - i'll put one up in the next couple of days..

Comment on Create a bootable EBS AMI from a running instance by Mateu

July 29th, 2010 @ 23:04 – permalink

When i execute ec2-register -n "AMI from S3" --architecture i386 --block-device-mapping /dev/sda1=snap-788e5c11:15:false this not work, the result is:

SYNOPSIS ec2reg (ec2-register) ec2reg [GENERAL OPTIONS] MANIFEST GENERAL NOTES Any command option/parameter may be passed a value of '-' to indicate that values for that option should be read from stdin. DESCRIPTION Register an AMI manifest for use with EC2. The MANIFEST parameter is the manifest (in S3) to register. e.g. mybucketname/image.manifest

GENERAL OPTIONS
 -K, --private-key KEY
      Specify KEY as the private key to use. Defaults to the value of the
      EC2_PRIVATE_KEY environment variable (if set). Overrides the default.

 -C, --cert CERT
      Specify CERT as the X509 certificate to use. Defaults to the value 
      of the EC2_CERT environment variable (if set). Overrides the default.

 -U, --url URL
      Specify URL as the web service URL to use. Defaults to the value of
      'https://ec2.amazonaws.com' or to that of the EC2_URL environment
      variable (if set). Overrides the default.

 --region REGION
      Specify REGION as the web service region to use.
      This option will override the URL specified by the "-U URL" option and EC2_URL environment variable.

 -v, --verbose
      Verbose output.

 -?, --help
      Display this help.

 -H, --headers
      Display column headers.

 --debug
      Display additional debugging information.

 --show-empty-fields
      Indicate empty fields.

 --connection-timeout TIMEOUT
      Specify a connection timeout TIMEOUT (in seconds).

 --request-timeout TIMEOUT
      Specify a request timeout TIMEOUT (in seconds).

Comment on Create a bootable EBS AMI from a running instance by Chris Anderton

July 31st, 2010 @ 21:22 – permalink

Hi Mateu

It looks to me like you are on an older version of the ec2 tools - check you are running the latest version to ensure they have support of the EBS volumes.

Chris
Comment on Create a bootable EBS AMI from a running instance by Chris Snyder

August 31st, 2010 @ 23:08 – permalink

Using dd to copy the root volume is not such a great idea, because changes to the disk during the copy operation can fuxxor the copy in interesting ways. My sshd_config got overwritten with syslog data, a very annoying bug indeed.

Better approach: 1) mkfs.ext3 TARGET 2) mount TARGET /migrate 3) rsync -ax --progress / /migrate 4) rm -rf /migrate/migrate 5) ... other changes 6) umount TARGET

Otherwise, excellent tip sheet and very helpful indeed.
Comment on Create a bootable EBS AMI from a running instance by Chris Anderton

September 24th, 2010 @ 18:22 – permalink

Thanks Chris - that is interesting, i did tussle between dd and rsync - i seem to remember there are some gotchas with the rsync approach too, but might be completely wrong! Thanks for dropping by - i'll adjust the instructions to offer rsync as an option.
Comment on Create a bootable EBS AMI from a running instance by jeremy

November 7th, 2010 @ 05:46 – permalink

Is it possible to convert a windows 2003 instance store backed to ebs backed? I need to add space to the C:\ partition that is running out of space and can't find a better way to increase the size without converting it to EBS. Any help would be great.
Comment on Create a bootable EBS AMI from a running instance by Kevin

February 17th, 2011 @ 18:41 – permalink

@jeremy... I found this pdf from cloudfront.net right before I found this article... http://d2fijcgs9oegyr.cloudfront.net/How%20to%20Convert%20S3-Backed%20Windows%20AMIs%20to%20EBS-Backed%20AMIs.pdf
Comment on Create a bootable EBS AMI from a running instance by vincent

June 26th, 2011 @ 17:04 – permalink

Hello Folks,

i get the same errors like Mateu.. and im using the latest ec2 Tools version..:-( i dont know what to do... Could somebody Help???

Regards, vincent
Comment on Create a bootable EBS AMI from a running instance by Tim Oxley

July 5th, 2011 @ 07:38 – permalink
Also getting this error:
```
ec2-register -n someapp --architecture x86_64 --block-device-mapping /dev/sda1=2e326c24:10:false

Client.InvalidParameterValue: Value (2e326bc4) for parameter virtualName is invalid. Expected format: 'ephemeral<NUMBER>'
```
Am I substituting the vars in incorrectly?

This post suggests that this whole thing isn't even possible. https://forums.aws.amazon.com/message.jspa?messageID=177188

I'm confused as to what is going on.
Comment on Create a bootable EBS AMI from a running instance by Chris Anderton

July 5th, 2011 @ 10:48 – permalink

Hi Tim

In the block device mapping you'd need to specify what that id relates to - e.g. snap-2e326c24 if it is a snapshot

Chris

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About this entry

Author: Chris Anderton
Published: April 19th, 2010 @ 21:43
Updated: September 24th, 2010 @ 20:33
Tags: ami, convert, ebs, ec2, s3
Comments: 10 comments

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