Introduction

In this guide, I’ll show you how to export a Docker volume and copy it to another machine. This process involves creating a backup (tarball) of the volume, transferring it to the target machine, and extracting the content into a new volume on the target machine. We’ll use a PostgreSQL container as an example.

Step 1: Create a Container to Access the Volume

First, create a temporary container to access the volume and create a tarball containing the volume’s contents.

Run the following command in the terminal:

docker run --rm -v drupal_postgres_data:/volume -v $(pwd):/backup busybox tar czvf /backup/volume_backup.tar.gz -C /volume .

Explanation:

  • docker run: Runs a Docker container.
  • --rm: Automatically removes the container after it completes its task.
  • -v drupal_postgres_data:/volume: Mounts the drupal_postgres_data volume to the /volume directory in the container.
  • -v $(pwd):/backup: Mounts the current directory to the /backup directory in the container.
  • busybox: A lightweight Docker image with basic Linux utilities.
  • tar czvf /backup/volume_backup.tar.gz -C /volume .: Creates a gzip-compressed tarball of the /volume directory.

Step 2: Copy the Tarball to the Local Filesystem

The tarball is now in your current directory. Use the scp command to copy this file to the target machine:

scp volume_backup.tar.gz user@target_machine:/path/to/destination

Explanation:

  • scp: Securely copies files over SSH.
  • volume_backup.tar.gz: The tarball file to copy.
  • user@target_machine: Username and address of the target machine.
  • /path/to/destination: Destination path on the target machine.

Step 3: Transfer the Tarball to the Target Machine

Ensure you have access rights and that the destination directory exists on the target machine.

Step 4: Extract the Tarball on the Target Machine

On the target machine, create a new Docker volume and extract the tarball into it.

1. Create a new Docker volume:

docker volume create drupal_postgres_data_new

2. Run a container to extract the tarball into the new volume:

docker run --rm -v drupal_postgres_data_new:/volume -v /path/to/destination:/backup busybox tar xzvf /backup/volume_backup.tar.gz -C /volume

Explanation:

  • docker run: Runs a Docker container.
  • --rm: Automatically removes the container after it completes its task.
  • -v drupal_postgres_data_new:/volume: Mounts the drupal_postgres_data_new volume to the /volume directory in the container.
  • -v /path/to/destination:/backup: Mounts the directory with the tarball to the /backup directory in the container.
  • busybox: The Docker image used.
  • tar xzvf /backup/volume_backup.tar.gz -C /volume: Extracts the tarball into the drupal_postgres_data_new volume.

Step 5: Use the New Volume in Docker Compose on the Target Machine

Edit the docker-compose.yml file to use the new volume:

version: '3.1'

services:
  db:
    image: postgres:14.2-alpine
    restart: always
    ports:
      - "5430:5432"
    environment:
      - POSTGRES_DB=postgres
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
    volumes:
      - drupal_postgres_data_new:/var/lib/postgresql/data
    networks:
      - drupal-nw

volumes:
  drupal_postgres_data_new:

networks:
  drupal-nw:

Then, restart the Docker Compose service:

docker-compose up -d

This command starts the services defined in the docker-compose.yml file.

Conclusion

By following these steps, you can successfully export a Docker volume from one machine and import it to another. This method ensures that the volume’s contents are accurately transferred and restored on the target machine.

💬 Bình luận