Sep 26, 2008

Snapshots of EBS Volumes

Continuing with the volume created in the post Sharing EBS Volumes Among Instances, in this post I show how to create a snapshot, create a new volume from that snapshot, and mount the new volume in an instance. Remember that the volume created in the previous post contained 1 file called readme.

Creating the Snapshot

First we look at the available volumes:

$ ec2-describe-volumes
VOLUME vol-4001e429 1 us-east-1c available 2008-09-25T09:51:48+0000

Then we make the snapshot:

$ ec2-create-snapshot vol-4001e429
SNAPSHOT snap-cb7493a2 vol-4001e429 pending 2008-09-26T11:48:30+0000

It is pending. We check the status until it the snapshot creation has completed:

$ ec2-describe-snapshots snap-cb7493a2
SNAPSHOT snap-cb7493a2 vol-4001e429 completed 2008-09-26T11:48:30+0000 100%

Creating a Volume from the Snapshot

Now that the snapshot is ready, we can create a new volume from it. Note that we create it in a different availability zone. The original volume resides in us-east-1c. The new volume will reside in us-east-1a.

$ ec2-create-volume –snapshot snap-cb7493a2 -z us-east-1a
VOLUME vol-9f00e5f6 1 snap-cb7493a2 us-east-1a creating 2008-09-26T11:52:37+0000

We wait until the volume is available:

$ ec2-describe-volumes
VOLUME vol-9f00e5f6 1 snap-cb7493a2 us-east-1a available 2008-09-26T11:52:37+0000
VOLUME vol-4001e429 1 us-east-1c available 2008-09-25T09:51:48+0000

Now we have two available volumes.

Mounting the New Volume in an Instance

Let’s launch an image so that we can verify that the newly created volume can be mounted and has the same contents as the original volume. Note that the instance is launched in the availability zone where the newly created volume resides.

$ ec2-run-instances ami-0757b26e -k gettingstarted-keypair -z us-east-1a

The AMI we use here is a public Ubuntu Desktop image.

$ ec2-describe-instances
RESERVATION r-ff4d9e96 190912652296 default
INSTANCE i-0fcf6c66 ami-0757b26e ec2-67-202-35-79.compute-1.amazonaws.com domU-12-31-38-00-6C-F6.compute-1.internal running gettingstarted-keypair 0 m1.small 2008-09-26T11:55:16+0000 us-east-1a aki-a71cf9ce ari-a51cf9cc

The instance is ready to be used. In another terminal we connect to the image and start the user-setup script. The GUI interaction to set up the user is not shown here.

$ ssh -i id_rsa-gettingstarted-keypair root@ec2-67-202-35-79.compute-1.amazonaws.com
The authenticity of host ‘ec2-67-202-35-79.compute-1.amazonaws.com (67.202.35.79)’ can’t be established.
RSA key fingerprint is ab:df:4e:78:b7:4d:59:3e:ae:6c:81:32:80:eb:bd:78.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added ‘ec2-67-202-35-79.compute-1.amazonaws.com,67.202.35.79′ (RSA) to the list of known hosts.
Linux domU-12-31-38-00-6C-F6 2.6.21.7-2.fc8xen #1 SMP Fri Feb 15 12:39:36 EST 2008 i686

The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

Amazon EC2 Ubuntu 7.10 gutsy base install AMI built by
Eric Hammond
For more information: http://ec2gutsy-desktop.notlong.com

root@domU-12-31-38-00-6C-F6:~# user-setup
Shadow passwords are now on.
Using `/usr/share/libgksu/debian/gconf-defaults.libgksu-sudo’ to provide `libgksu-gconf-defaults’.

Time to attach the volume (in the original terminal):

$ ec2-attach-volume vol-9f00e5f6 -i i-0fcf6c66 -d /dev/sdh
ATTACHMENT vol-9f00e5f6 i-0fcf6c66 /dev/sdh attaching 2008-09-26T12:01:15+0000
$ ec2-describe-volumes
VOLUME vol-9f00e5f6 1 snap-cb7493a2 us-east-1a in-use 2008-09-26T11:52:37+0000
ATTACHMENT vol-9f00e5f6 i-0fcf6c66 /dev/sdh attached 2008-09-26T12:01:15+0000
VOLUME vol-4001e429 1 us-east-1c available 2008-09-25T09:51:48+0000

Let’s see whether it is available. Connect to the desktop as described in Preparing for Amazon AWS Usage.

Device available in Ubuntu

In the terminal connected to the instance, we can mount the volume now:

root@domU-12-31-38-00-6C-F6:~# mkdir /mnt/my-volume
root@domU-12-31-38-00-6C-F6:~# mount /dev/sdh /mnt/my-volume

Now the volume should be mounted as my-volume and accessible. Let’s verify that by opening a file browser on that volume.

Volume mounted in Ubuntu

Indeed, the readme file that was on the original volume is also on the new volume created from the snapshot.