Docker volume backup. Courtesy of https://stackoverflow.com/a/26339869/5203187

volume_backup.sh

#!/bin/bash
# This script allows you to backup a single volume from a container
# Data in given volume is saved in the current directory in a tar archive.
CONTAINER_NAME=$1
VOLUME_NAME=$2
VOLUME_NAME_SANITIZED=$(echo $VOLUME_NAME | sed s#/#_#2g)

usage() {
  echo "Usage: $0 [container name] [volume name]"
  exit 1
}

if [ -z $CONTAINER_NAME ]
then
  echo "Error: missing container name parameter."
  usage
fi

if [ -z $VOLUME_NAME ]
then
  echo "Error: missing volume name parameter."
  usage
fi

sudo docker run --rm --volumes-from $CONTAINER_NAME -v $(pwd):/backup busybox tar czvf /backup/$VOLUME_NAME_SANITIZED.tar.gz $VOLUME_NAME