Step-by-Step Guide to Copying or Moving Docker Containers Between Hosts

Key Notes

  • Understand the process of saving and transferring Docker container images.
  • Export and import Docker volumes effectively.
  • Consider utilizing Docker Compose for more complex deployments.

Unlocking the Secrets to Moving Docker Containers

In the dynamic world of software development, Docker containers serve as efficient packages, enabling developers to deploy applications seamlessly across various environments. As projects evolve, the ability to transfer or replicate these containers becomes crucial for optimizing resource utilization and operational efficiency. This guide delves into the step-by-step process of copying and moving Docker containers and their associated volumes from one Linux host to another.

Save Your Container Image on the Source Host

Step 1: List Available Docker Containers

Begin by listing the available Docker containers running on your system. Identify the container you want to export, for example, an Nginx instance:

Step 2: Stop the Desired Container

Stop the selected container before exporting it to avoid data corruption:

Step 3: Commit Current Container State to Image

Preserve the state of your container by committing it to a new Docker image to keep all modifications and data intact:

Pro Tip: Use docker commit -p=false CONTAINER_NAME new_image_name to avoid pausing the container, though it increases the risk of data inconsistencies.

Step 4: Save the Docker Image to a Tar Archive

Save the new Docker image to an archive file (e.g., mycontainerimage.tar ) before transferring it to the target host:

Export the Docker Volume from Your Container

Step 5: Install Git and Download Volume Export Script

To handle the export of your volumes, first ensure Git is installed and then download the volume export script:

Step 6: Change Script Permissions and Run Export

Set the correct permission bits for the script, and execute it to extract the associated volumes for your container:

Step 7: Transfer Volume Files to Remote Machine

Send the newly archived volume files using your preferred method, such as scp, to the target host:

Load Your Container Image on the Destination Host

Step 8: Load the Docker Image into Docker Daemon

Log in to your remote host, then run the command to load the Docker image into the Docker daemon:

Step 9: Create Your Container Using the Loaded Image

Use docker create to initialize the new container, specifying any necessary run flags:

Step 10: Start the Imported Container

Confirm that your imported image is working properly by running: docker start CONTAINER_NAME.

Import the Docker Volume into Your Container

Step 11: Download and Configure the Volume Import Script

Download the same Docker volume helper script on your new host and set the appropriate permissions:

Step 12: Load the Volume from Tar Archive

Run the volume import script with your .tar file to restore the volumes on your new container:

Step 13: Test Volume Data Inside Your Container

Verify that the container is loading the data correctly by checking its internal configuration:

Transfer Your Image Without the File

Step 14: Use SSH for Direct Image Transfer

Instead of creating a tar file, you can directly transfer the image using this command through an SSH pipe:

Step 15: Start Your New Container

After transferring and initializing correctly, run docker start CONTAINER_NAME to verify it’s operational:

Utilize Docker Compose for Full Docker Deployment Migration

Step 16: Confirm Docker Compose Plugin Availability

Ensure that Docker Compose is enabled in your environment:

Step 17: Create the Docker Compose Configuration

Create a directory in your home to hold the Docker Compose file and build the docker-compose.yml file for your application:

Step 18: Launch Your Application Using Docker Compose

Run Docker Compose to deploy your application as you specified in the configuration file and test its functionality:

Additional Tips

  • Always validate the integrity of your Docker images and volumes after transfer.
  • Document your Docker networking setups for smooth transitions across hosts.
  • Consider using Docker Swarm or Kubernetes for automating application deployment.

Summary

Transferring Docker containers and their associated data between Linux hosts involves utilizing commands to save images, export volumes, and ensure proper reconfiguration on the destination host. By following these steps, you can successfully manage your container ecosystem across different systems while maintaining functionality and consistency.

Conclusion

Mastering the process of moving Docker containers not only expands your technical toolkit, but also enhances your deployment strategies across various environments. Embrace these practices as you continue to explore the limitless possibilities of containerization.

FAQ (Frequently Asked Questions)

Can I copy a running Docker container?

Yes, but it’s best to stop the container first to avoid complications. Use the docker commit command to save its state.

What if my Docker container has a large size?

Consider transferring without creating a file using the SSH pipe method to save space and time.