EBS Volumes – deleteOnTermination ?

When using EC2 instances with EBS backed storage, whether or not your instances are setup to delete their EBS volumes on termination can be a big deal — especially if you burn AMIs and provision instances over and over. You could find yourself with many EBS volumes that are unused and pay for lots of storage you don’t use.

Audit your systems with a command similar to this one – the last column in the output is whether or not deleteOnTermination is set:

for instanceid in $(ec2-describe-instances | awk '/INSTANCE/ {print $2}')
do
  echo "InstanceID: ${instanceid}"
  ec2-describe-instance-attribute -v -b ${instanceid} | egrep "BLOCKDEVICE.*false"

done

If you see output like the following:

InstanceID: i-xxxxxxxx            
  BLOCKDEVICE     /dev/sda1        vol-xxxxxxxx    2013-05-24T20:32:05.000Z        false   

…you have instances with volumes that will not delete when the instance is terminated.

To fix this, run the following command for each instance, and burn another AMI:

ec2-modify-instance-attribute -b '/dev/sda1=vol-xxxxxxxx:true' i-xxxxxxxx

I made a simple bash script that will iterate over all EC2 instances in an account and modify the first volume that is not set to delete on termination to do so. Note that this limitation requires the script to be re-run multiple times, depending on the number of EBS volumes attached to each instance that might need this flag set.

#!/bin/bash

#
# Audit instances to set all volumes to deleteOnTermination
#

for instanceid in $(ec2-describe-instances | awk '/INSTANCE/ {print $2}')
do
  IFS='\n'
  result=$(ec2-describe-instance-attribute -v -b ${instanceid} | egrep "BLOCKDEVICE.*false")
  for line in ${result}
  do  
    echo ${line}
    device=$(echo ${line} | head -n 1 | awk '{print $2}')
    volume=$(echo ${line} | head -n 1 | awk '{print $3}')
    ec2-modify-instance-attribute -b "${device}=${volume}:true" ${instanceid}
    if [ $? -gt 0 ] 
    then
      echo "command failed for ${instanceid}"
    fi  
  done
  unset IFS
done

exit 0;

Note that for some instances, multiple volumes were set properly and for some it was not. I did not take the time to troubleshoot this discrepancy or write a proper loop at this point. Patches welcome.