Backup & restore a local volume from docker.

volume-command.sh

#!/bin/sh

BUSYBOX_IMAGE=${BUSYBOX_IMAGE:-busybox}
BUSYBOX_IMAGE_ID=$(docker images -q $BUSYBOX_IMAGE | head -n1)

check_busybox() {
  if [ -z "$BUSYBOX_IMAGE_ID" ]; then
    echo >&2 "error: $BUSYBOX_IMAGE image not found."
    exit 1
  fi  
}

case "$1" in
  export)
    check_busybox
    docker run --rm -v $2:/_data:ro $BUSYBOX_IMAGE_ID tar c -zf - -C / _data > $2.tar.gz
    ;;  
  import)
    check_busybox
    docker volume create $2
    docker run --rm -i -v $2:/_data:rw $BUSYBOX_IMAGE_ID tar x -zf - -C / < $3
    ;;  
  *)  
    echo >&2 "usage: $0 export <volume-name>"
    echo >&2 "       $0 import <volume-name> <volume-file>"
    ;;  
esac