snapshot-source-roots.sh

#!/usr/bin/env zsh 

# Given a list of instance-id in an AWS region, it makes a snapshot of the root
# volume (assumed to be /dev/sda!) and copies it to the target region.
#
# The root volume is remounted 'ro' on each instance - so this script must
# be run from somewhere that can SSH to the server (possibly may require
# special firewall rules to be applied).
#
# Output is written to ${OUTPUT_FILE}

set -e

CERT=$HOME/.ssh/aws/orel-migration-test.pem
SSH_USER="root" # Set this to login account associated with CERT
SOURCE_REGION="us-east-1"
TARGET_REGION="ap-southeast-2"
OUTPUT_FILE="source-instance-snapshots.csv"

for INSTANCE_ID in "$@" ; do
  echo "Processing ${INSTANCE_ID}"
  INFO=$(ec2-describe-instances ${INSTANCE_ID} --region ${SOURCE_REGION})

  INSTANCE_IP=$(echo ${INFO} | awk '/^INSTANCE/ { print $14 }')
  if [[ -z $INSTANCE_IP ]] ; then 
    echo "unable to get IP (got ${INSTANCE_IP})" 
    exit
  fi

  VOLUME_ID=$(echo $INFO | awk '$1 == "BLOCKDEVICE" && $2 == "/dev/sda" { print $3 }')
  if [ -z "$VOLUME_ID" ] ; then 
    echo "unable to get volume id" 
    exit
  fi

  echo " remounting / read-only"
  ssh -i ${CERT} -tt ${SSH_USER}@${INSTANCE_IP} sudo mount -f -o ro,remount /

  echo " creating snapshot"
  SNAPSHOT_ID=$(ec2-create-snapshot ${VOLUME_ID} --region ${SOURCE_REGION} | cut -f 2)

  echo " remounting rw" 
  ssh -i ${CERT} -tt ${SSH_USER}@${INSTANCE_IP} sudo mount -f -o rw,remount /

  echo " triggering copy to target region"
  COPIED_SNAPSHOT_ID=$(ec2-copy-snapshot -s ${SNAPSHOT_ID} --source-region ${SOURCE_REGION} --region ${TARGET_REGION} -d "Migrated snapshot ${INSTANCE_ID} ${VOLUME_ID}" | awk '/SNAPSHOT/ { print $2 }')

  echo " deleting source snapshot"
  ec2-delete-snapshot ${SNAPSHOT_ID} --region ${SOURCE_REGION}

  echo " completed ${INSTANCE_ID}"

  echo ${SOURCE_REGION},${INSTANCE_ID},${INSTANCE_IP},${VOLUME_ID},${COPIED_SNAPSHOT_ID} >> $OUTPUT_FILE
done