vackup

#!/usr/bin/env bash
# Docker Volume File Backup and Restore Tool
# Easily tar up a volume on a local (or remote) engine
# Inspired by CLIP from Lukasz Lach

set -Eeo pipefail

handle_error() {
  case $# in
    1) LINE_NUMBER=$1; EXIT_CODE=$? ;;
    2) LINE_NUMBER=$1; EXIT_CODE=$2 ;;
    *) LINE_NUMBER=$LINENO; EXIT_CODE=1 ;;
  esac

  if [ -n "${VACKUP_FAILURE_SCRIPT}" ]; then
    /bin/bash "${VACKUP_FAILURE_SCRIPT}" "$LINE_NUMBER" "$EXIT_CODE"
  fi

  exit "$EXIT_CODE"
}

trap 'handle_error $LINENO' ERR

usage() {
cat <<EOF

"Docker Volume Backup". Replicates container image management commands for container volumes.

export/import copies files between a host tarball and a volume.
  For making volume backups and restores on your local file system.

save/load copies files between a container image and a container volume.
  For storing container volumes in images and push/pulling to registries.

Usage:

vackup export [OPTIONS] VOLUME FILE
  Creates a gzip'ed tarball in current directory from a container volume

  Options:
    --owner=UID[:GID]       Change the ownership of the exported archive on Linux (won't have any effect on macOS)

vackup import FILE VOLUME
  Extracts a gzip'ed tarball into a container volume

vackup save VOLUME IMAGE
  Copies a container volume to a busybox container image in the /volume-data directory

vackup load IMAGE VOLUME
  Copies /volume-data from a container image to a container volume

EOF
}

error() {
    if [ "$1" == 'u' ] || [ "$1" == 'usage' ]; then
        USAGE=1
        MESSAGE=$2
        CODE=$3
    else
        USAGE=0
        MESSAGE=$1
        CODE=$2
    fi

    if [ -z "$MESSAGE" ]; then
        echo 1>&2 'Error'
    else
        echo 1>&2 "Error: $MESSAGE"
    fi

    if [ $USAGE -eq 1 ]; then
        usage 1>&2
    fi

    if [ -z "$CODE" ]; then
        CODE=1
    fi

    LINE_NUMBER=$(caller | awk '{ print $1 }')
    handle_error "$LINE_NUMBER" "$CODE"
}

fulldirname() {
  DIRECTORY=$(dirname "$1")

  case "$DIRECTORY" in
    /*) ;;
    *) DIRECTORY="$(pwd)/$DIRECTORY" ;;
  esac

  # Use realpath if available, else fallback to cd/pwd for macOS compatibility
  if command -v realpath >/dev/null 2>&1; then
    DIRECTORY=$(realpath "$DIRECTORY")
  else
    DIRECTORY=$(cd "$DIRECTORY" && pwd)
  fi

  echo "$DIRECTORY"
}

is_digits() {
    case "$1" in
      *[!0-9]*) return 1 ;;
      *) return 0 ;;
    esac
}

if [ -z "$1" ] || [ "$1" == "-h" ] || [ "$1" == "--help" ]; then
    usage
    exit 0
fi

cmd_export() {
    OWNER=''

    while [ $# -ne 0 ]; do
        case "$1" in
          -*)
            OPTION="$1"
            shift

            case "$OPTION" in
              --owner) error usage "'$OPTION' option requires a value" ;;
              --owner=*)
                if [ -n "$OWNER" ]; then
                    error usage "'--owner' option may only be used once"
                fi

                OWNER=${OPTION#--owner=}

                if [ -z "$OWNER" ]; then
                    error usage "'$OPTION' option requires a non-empty value"
                fi

                USER=$(echo "$OWNER" | cut -d':' -f1)
                GROUP=$(echo "$OWNER" | cut -d':' -f2)

                if [ -z "$USER" ]; then
                    error usage "The UID in the '$OPTION' option can not be empty"
                fi
                if [ -z "$GROUP" ]; then
                    GROUP="$USER"
                fi

                if ! is_digits "$USER" || ! is_digits "$GROUP"; then
                    error usage "UID:GID in the '$OPTION' option may only contain digits"
                fi

                OWNER="$USER:$GROUP"
              ;;
              *) error usage "'$OPTION' is not a recognized export option" ;;
            esac
          ;;
          *) break ;;
        esac
    done

    VOLUME_NAME="$1"
    FILE_NAME="$2"

    if [ -z "$VOLUME_NAME" ] || [ -z "$FILE_NAME" ]; then
        error usage 'Not enough arguments'
    fi

    if ! docker volume inspect --format '{{.Name}}' "$VOLUME_NAME";
    then
        error "Volume $VOLUME_NAME does not exist"
    fi

# TODO: check if file exists on host, if it does, create overwrite option and check if set

    DIRECTORY=$(fulldirname "$FILE_NAME")
    FILE_NAME=$(basename "$FILE_NAME")

    if ! docker run --rm \
      -v "$VOLUME_NAME":/volume-data \
      -v "$DIRECTORY":/mount-volume \
      busybox \
      /bin/sh -c 'tar -cvzf /mount-volume/'"'$FILE_NAME'"' -C /volume-data . && chown '"'${OWNER:-"$(id -u):$(id -g)"}'"' /mount-volume/'"'$FILE_NAME'";
    then
        error 'Failed to start busybox backup container'
    fi

    echo "Successfully tar'ed volume $VOLUME_NAME into file $FILE_NAME"
}

cmd_import() {
    FILE_NAME="$1"
    VOLUME_NAME="$2"

    if [ -z "$VOLUME_NAME" ] || [ -z "$FILE_NAME" ]; then
        error usage 'Not enough arguments'
    fi

    if ! docker volume inspect --format '{{.Name}}' "$VOLUME_NAME";
    then
        echo "Warning: Volume $VOLUME_NAME does not exist, creating..."
        docker volume create "$VOLUME_NAME"
    fi

    if [ ! -r "$FILE_NAME" ]; then
        echo "Error: Could not find or open tar file $FILE_NAME"
        exit 1
    fi

    if [ -d "$FILE_NAME" ]; then
        echo "Error: $FILE_NAME is a directory"
        exit 1
    fi

    DIRECTORY=$(fulldirname "$FILE_NAME")
    FILE_NAME=$(basename "$FILE_NAME")

    if ! docker run --rm \
      -v "$VOLUME_NAME":/volume-data \
      -v "$DIRECTORY":/mount-volume \
      busybox \
      tar -xvzf /mount-volume/"$FILE_NAME" -C /volume-data;
    then
        error 'Failed to start busybox container'
    fi

    echo "Successfully unpacked $FILE_NAME into volume $VOLUME_NAME"
}

cmd_save() {
    VOLUME_NAME="$1"
    IMAGE_NAME="$2"

    if [ -z "$VOLUME_NAME" ] || [ -z "$IMAGE_NAME" ]; then
        error usage 'Not enough arguments'
    fi

    if ! docker volume inspect --format '{{.Name}}' "$VOLUME_NAME";
    then
        error "Volume $VOLUME_NAME does not exist"
    fi

    if ! docker run \
      --pull missing \
      -v "$VOLUME_NAME":/mount-volume \
      busybox \
      cp -Rp /mount-volume/. /volume-data/;
    then
        error 'Failed to start busybox container'
    fi

    # FIXME: this command assumes that no containers started between the cp and container rm commands. 
    #   It would be safer to capture ID of the busybox container on start, then delete that ID 
    CONTAINER_ID=$(docker ps -lq)

    docker commit -c "LABEL com.docker.desktop.volume-contents.action=true" -m "saving volume $VOLUME_NAME to /volume-data" "$CONTAINER_ID" "$IMAGE_NAME"

    docker container rm "$CONTAINER_ID"

    echo "Successfully copied volume $VOLUME_NAME into image $IMAGE_NAME, under /volume-data"
}

cmd_load() {
    IMAGE_NAME="$1"
    VOLUME_NAME="$2"

    if [ -z "$VOLUME_NAME" ] || [ -z "$IMAGE_NAME" ]; then
        error usage 'Not enough arguments'
    fi

    if ! docker volume inspect --format '{{.Name}}' "$VOLUME_NAME";
    then
      echo "Warning: Volume $VOLUME_NAME does not exist, creating..."
      docker volume create "$VOLUME_NAME"
    fi

    # FIXME: this command assumes the image we're copying from has the cp command available
    if ! docker run --rm \
      -v "$VOLUME_NAME":/mount-volume \
      "$IMAGE_NAME" \
      cp -Rp /volume-data/. /mount-volume/;
    then
        error "Failed to start container from $IMAGE_NAME"
    fi

    echo "Successfully copied /volume-data from $IMAGE_NAME into volume $VOLUME_NAME"
}

COMMAND="$1"
shift
case "$COMMAND" in
  export) cmd_export "$@" ;;
  import) cmd_import "$@" ;;
  save) cmd_save "$@" ;;
  load) cmd_load "$@" ;;
  *) echo "Error: '$COMMAND' is not a recognized command" ; usage ;;
esac

exit 0