Backup and restore docker volume data

db-volume-backup.sh

#!/usr/bin/env bash
#
# Script to backup and restore docker volume data
#
# Example:
#
#   BACKUPPED_PATH=/var/lib/postgresql/data BACKUPPED_VOLUME=my-db-volume ./db-volume-backup.sh backup my-db-volume-backup
#

set -e
#set -x

OP="$1"
BACKUP_NAME="$2"

usage() {
  cat <<EOF
Backup and restore docker volume data.

Usage:
  $(basename $0) (backup|restore) (backup-name)
EOF
}

if [[ "$BACKUP_NAME" == "" ]]
then
  usage
  exit 1
fi

checks() {
  if docker ps --filter "volume=${BACKUPPED_VOLUME?}" --format "{{.Names}}" | grep Up
  then
    echo >&2 "Containers using ${BACKUPPED_VOLUME?} volume found running. Stop them before retry."
    exit 3
  fi
}

case "$OP" in
  backup)
    checks

    # Create a temporary container which mounts the volume
    docker run --rm -v ${BACKUPPED_VOLUME?}:${BACKUPPED_PATH?} -d --name backup-${BACKUPPED_VOLUME?} busybox sleep 1d >/dev/null

    temp_dir=$(mktemp -d)

    trap "rm -rf "$temp_dir" & docker stop backup-${BACKUPPED_VOLUME?} &" EXIT

    # Use docker cp to copy data to the host
    docker cp backup-${BACKUPPED_VOLUME?}:${BACKUPPED_PATH?} "$temp_dir/backup"

    # Stop and remove the temporary container
    docker stop backup-${BACKUPPED_VOLUME?}
    trap "rm -rf "$temp_dir" &" EXIT

    echo "Compressing..."
    pwd=$(pwd)
    (cd "$temp_dir" && tar czf "$pwd/${BACKUP_NAME?}.tar.gz" backup)
    echo "Saved: $(du -h -s ${BACKUP_NAME?}.tar.gz)"
    rm -rf "$temp_dir"
    trap "" EXIT

    ;;
  restore)
    checks

    # Create a temporary container which mounts the volume
    docker run --rm -v ${BACKUPPED_VOLUME?}:${BACKUPPED_PATH?} -d --name backup-${BACKUPPED_VOLUME?} busybox sleep 1d >/dev/null

    temp_dir=$(mktemp -d)

    trap "rm -rf "$temp_dir" & docker stop backup-${BACKUPPED_VOLUME?} &" EXIT

    echo "From: $(du -h -s ${BACKUP_NAME?}.tar.gz)"
    
    # Extract the backup if it's compressed
    tar xzf ${BACKUP_NAME?}.tar.gz -C "$temp_dir"

    # Use docker cp to copy data to the volume
    docker cp "$temp_dir/backup/." backup-${BACKUPPED_VOLUME?}:${BACKUPPED_PATH?} 

    # Stop and remove the temporary container
    docker stop backup-${BACKUPPED_VOLUME?}
    rm -rf "$temp_dir"
    trap "" EXIT
    ;;
  *)
    usage
    exit 2
    ;;
esac

Example run,
of backup:

% BACKUPPED_PATH=/var/lib/postgresql/data BACKUPPED_VOLUME=backend_db ./db-volume-backup.sh backup backend_db
Successfully copied 950MB to /var/folders/tn/grglkq4521sgkw60t257zmw00000gq/T/tmp.heBAqDkj/backup
backup-backend_db
Compressing...
Saved: 176M	backend_db.tar.gz

and restore:

% BACKUPPED_PATH=/var/lib/postgresql/data BACKUPPED_VOLUME=backend_db ./db-volume-backup.sh restore backend_db
From: 176M	backend_db.tar.gz
Successfully copied 950MB to backup-backend_db:/var/lib/postgresql/data
backup-backend_db