Mount a EBS volume (not snapshot) to Elastic Beanstalk EC2

I have found a solution. It could be improved by removing the "sleep 10" but unfortunately that required because aws ec2 attach-volume is async and returns straight away before the attachment takes place.

container_commands:
  01mount:
    command: "aws ec2 attach-volume --volume-id vol-XXXXXX --instance-id $(curl -s http://169.254.169.254/latest/meta-data/instance-id) --device /dev/sdh"
    ignoreErrors: true
  02wait:
    command: "sleep 10"
  03mkdir:
    command: "mkdir /data"
    test: "[ ! -d /data ]"
  04mount:
    command: "mount /dev/sdh /data"
    test: "! mountpoint -q /dev/sdh"

Note. Ideally it would be run in commands section not container_commands but the environment variables are not set in time.

To add to @Simon's answer (to avoid traps for the unwary):

• If the persistent storage being mounted will ultimately be used inside a Docker container (e.g. if you're running Jenkins and want to persist jenkins_home), you need to restart the docker container after running the mount.
• You need to have the 'ec2:AttachVolumes' action permitted against both the EC2 instance (or the instance/* ARN) and the volume(s) you want to attach (or the volume/* ARN) in the EB assumed role policy. Without this, the aws ec2 attach-volume command fails.
• You need to pass in the --region to the aws ec2 ... command as well (at least, as of this writing)

Here's a config file that you can drop in .ebextensions. You will need to provide the VOLUME_ID that you want to attach. The test commands make it so that attaching and mounting only happens as needed, so that you can eb deploy repeatedly without errors.

container_commands:
  00attach:
    command: |
      export REGION=$(/opt/aws/bin/ec2-metadata -z | awk '{print substr($2, 0, length($2)-1)}')
      export INSTANCE_ID=$(/opt/aws/bin/ec2-metadata -i | awk '{print $2}')
      export VOLUME_ID=$(aws ec2 describe-volumes --region ${REGION} --output text --filters Name=tag:Name,Values=tf-trading-prod --query 'Volumes[*].VolumeId')

      aws ec2 attach-volume --region ${REGION} --device /dev/sdh --instance-id ${INSTANCE_ID} --volume-id ${VOLUME_ID}
      aws ec2 wait volume-in-use --region ${REGION} --volume-ids ${VOLUME_ID}
      sleep 1
    test: "! file -E /dev/xvdh"
  01mkfs:
    command: "mkfs -t ext3 /dev/xvdh"
    test: "file -s /dev/xvdh | awk '{print $2}' | grep -q data"
  02mkdir:
    command: "mkdir -p /data"
  03mount:
    command: "mount /dev/xvdh /data"
    test: "! mountpoint /data"