How to move Docker containers between different hosts?

I cannot find a way of moving docker running containers from one host to another.

Is there any way I can push my containers to repositories like we do for images ? Currently, I am not using data volumes to store the data associated with applications running inside containers. So some data resides inside containers, which I want to persist before redesigning the setup.

Answers


You cannot move a running docker container from one host to another.

You can commit the changes in your container to an image with docker commit, move the image onto a new host, and then start a new container with docker run. This will preserve any data that your application has created inside the container.

Nb: It does not preserve data that is stored inside volumes; you need to move data volumes manually to new host.


alternatively, if you do not wish to push to a repository:

1) Export the container to a tarball

     docker export <CONTAINER ID> > /home/export.tar

2) Move your tarball to new machine

3) Import it back

     cat /home/export.tar | docker import - some-name:latest

What eventually worked for me, after lot's of confusing manuals and confusing tutorials, since Docker is obviously at time of my writing at peek of inflated expectations, is:

  1. Save the docker image into archive: docker save image_name > image_name.tar
  2. copy on another machine
  3. on that other docker machine, run docker load in a following way: cat image_name.tar | docker load

Export and import, as proposed in another answers does not export ports and variables, which might be required for your container to run. And you might end up with stuff like "No command specified" etc... When you try to load it on another machine.

So, difference between save and export is that save command saves whole image with history and metadata, while export command exports only files structure (without history or metadata).


From Docker documentation:

docker export does not export the contents of volumes associated with the container. If a volume is mounted on top of an existing directory in the container, docker export will export the contents of the underlying directory, not the contents of the volume. Refer to Backup, restore, or migrate data volumes in the user guide for examples on exporting data in a volume.

Other external tools: In order to move a container with its associated data volume you can use Flocker https://clusterhq.com/flocker/introduction/


Use this script: https://github.com/ricardobranco777/docker-volumes.sh

This does preserve data in volumes.

Example usage:

# Stop the container   
docker stop $CONTAINER

# Create a new image   
docker commit $CONTAINER $CONTAINER

# Save image
docker save -o $CONTAINER.tar $CONTAINER

# Save the volumes (use ".tar.gz" if you want compression)
docker-volumes.sh $CONTAINER save $CONTAINER-volumes.tar

# Copy image and volumes to another host
scp $CONTAINER.tar $CONTAINER-volumes.tar $USER@$HOST:

# On the other host:
docker load -i $CONTAINER.tar
docker create --name $CONTAINER [<PREVIOUS CONTAINER OPTIONS>] $CONTAINER

# Load the volumes
docker-volumes.sh $CONTAINER load $CONTAINER-volumes.tar

# Start container
docker start $CONTAINER

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