Docker Container Migration

What is Container Migration?

Container migration involves transferring running container data, configuration, and file systems across hosts. It ensures seamless portability and minimizes downtime during application reallocation or scaling.

Migrating Using Docker Images

Save a container image as a tar file:

docker commit mycontainer myimage
docker save -o myimage.tar myimage

Transfer the tar file to the new host and load it:

docker load -i myimage.tar

Migrating Volumes & Persistent Data

Use tar and rsync to copy Docker volumes:

docker volume inspect myvolume
sudo tar czf myvolume.tar.gz /var/lib/docker/volumes/myvolume

Transfer the archive and extract it on the new host:

sudo tar xzf myvolume.tar.gz -C /var/lib/docker/volumes

Ensure volume names match or use bind mounts for portability.

Moving Containers with Docker Compose

Copy your docker-compose.yml to the new host and run:

docker-compose up -d

Ensure you copy associated volumes or use external databases and caches.

Live Migration with CRIU (Experimental)

Checkpoint and restore containers using CRIU (on Linux only):

docker checkpoint create mycontainer checkpoint1

Copy the checkpoint folder and restore:

docker start --checkpoint checkpoint1 mycontainer

Note: CRIU must be installed and configured on both hosts.

Best Strategies for Different Use Cases

• Dev to staging: Push to Docker registry or use save/load
• Live system migration: Use commit and volume sync
• Stateful applications: Use Docker volumes and persistent storage migration
• Rolling updates: Use CI/CD and Docker Swarm/Kubernetes for smooth transitions

Docker container migration is flexible, supporting image export, volume backups, and advanced live migration tools. Choose the right strategy based on your environment, performance needs, and downtime tolerance.