How to backup and restore a Docker Container?

Docker containers provide a packaged environment for applications, making them portable and lightweight while allowing version control. Sometimes you need to create snapshots or backups of running containers for emergency rollbacks or to preserve specific states. This article covers how to backup and restore Docker containers using built-in commands.

Note: The backup methods described here work for containers with embedded data. For containers using separate data volumes, you must create separate backups for each volume.

Backing up a Docker Container

The backup process involves creating a snapshot of the container's current state and saving it as an image. This allows you to preserve the exact configuration and data at a specific point in time.

Step 1: Find the Container ID

First, identify the container you want to backup by listing all containers:

sudo docker ps -a

Copy the Container ID of the target container from the output.

Step 2: Create a Container Snapshot

Use the docker commit command to create an image from the container's current state:

sudo docker commit -p <CONTAINER_ID> <BACKUP_NAME>

The -p flag pauses the container during the commit process to ensure data consistency.

Example:

sudo docker commit -p 5c2f44fbb535 backup-ubuntu

Step 3: Save as TAR File (Local Backup)

To save the backup image as a TAR file on your local machine:

sudo docker save -o ~/backup-ubuntu.tar backup-ubuntu

Verify the TAR file was created:

sudo ls -l ~/backup-ubuntu.tar

Step 4: Push to Docker Registry (Remote Backup)

Alternatively, push the backup image to Docker Hub or another registry:

sudo docker login
sudo docker tag backup-ubuntu username/backup-ubuntu:tag
sudo docker push username/backup-ubuntu:tag

Replace username with your Docker Hub username and tag with a version identifier.

Restoring a Docker Container

Restoration involves loading the backup image and creating a new container instance from it.

Restore from TAR File

If you have a local TAR backup, load it using:

sudo docker load -i ~/backup-ubuntu.tar

Confirm the image was restored:

sudo docker images

Restore from Docker Registry

If the backup was pushed to a registry, pull it back:

sudo docker pull username/backup-ubuntu:tag

Run the Restored Container

Create a new container instance from the restored image:

sudo docker run -ti backup-ubuntu:tag

The -ti flags provide an interactive terminal session.

Container Migration

To migrate containers between machines, combine backup and restore processes:

• Registry Method: Push the backup to a registry from the source machine, then pull it on the target machine.

• TAR Method: Create a TAR backup, transfer the file to the target machine, then load and run it.

Comparison of Backup Methods

Conclusion

Docker container backup and restoration enables you to preserve application states and migrate containers between environments. Use docker commit and docker save for local backups, or combine docker commit with registry operations for remote backups. Choose the method that best fits your infrastructure and workflow requirements.