Cron Script To Snapshot Any Attached EBS Volume

If you would like to cron snapshots of any attached volume to an instance, you can use the following script. It uses the EC2 command line tools to see what volumes are currently attached to this instance, and takes a snapshot. Make sure to replace all the variables on the top of the script to match your own.

#!/bin/bash

export JAVA_HOME=/usr/java/default
export EC2_HOME=/vol/snap/ec2-api-tools-1.3-26369
export EC2_PRIVATE_KEY=[PATH-TO-YOUR-PRIVATE-KEY]
export EC2_CERT=[PATH-TO-YOUR-CERT]
export AWS_ACCESS_KEY_ID="[YOUR-ACCESS-KEY]"
export AWS_SECRET_ACCESS_KEY="[YOUR-SECRET-KEY]"

INSTANCE_ID=`curl -s http://169.254.169.254/latest/meta-data/instance-id`
echo "Instance ID is $INSTANCE_ID"
VOLUMES=`$EC2_HOME/bin/ec2-describe-volumes | grep "ATTACHMENT" | grep "$INSTANCE_ID" | awk '{print $2}'`
echo "Volumes are: $VOLUMES"

for VOLUME in $VOLUMES; do
        echo "Snapping Volume $VOLUME"
        DEVICE=`$EC2_HOME/bin/ec2-describe-volumes $VOLUME | grep "ATTACHMENT" | grep "$INSTANCE_ID" | awk '{print $4}'`
        echo "Device is $DEVICE"
        MOUNTPOINT=`df | grep "$DEVICE" | awk '{print $6}'`
        echo "Mountpoint is $MOUNTPOINT"

        # Snapshot
        SNAPSHOT_ID=`$EC2_HOME/bin/ec2-create-snapshot $VOLUME`

        echo "Snapshotted: $SNAPSHOT_ID"

done

If you’re wondering why $MOUNTPOINT is important (it’s not used here after all), it’s because you might want to freeze your filesystem if it’s XFS, so you could safely take a snapshot of a MySQL database for example. So you could easily wrap the snapshot create command with this:

        # freeze
        xfs_freeze -f $MOUNTPOINT

        # Snapshot
        SNAPSHOT_ID=`$EC2_HOME/bin/ec2-create-snapshot $VOLUME`

        # unfreeze
        xfs_freeze -u $MOUNTPOINT

And if you are indeed using this script to snapshot a volume with MySQL on it, you need also to flush tables with read lock, and gather information on master and slave positions. For this task you can use Eric Hammond‘s script, and incorporate it to the cron script. (You can read more about MySQL and XFS on EC2 on the AWS site).