How to Copy/Move a Docker Container to Another Host

Spread the love

Since Docker containers are little boxes of software, you can easily copy and move them around from computer to computer. It may be that you worked on a Docker instance on your local computer and decided to move it to a more powerful server. Or maybe you just want to deploy your custom container on multiple computers, “copy and paste” it around. Other times, you may be dissatisfied with a cloud-computing provider and want to switch to a different one. Here, we show you how to move your existing Docker container image and data volumes from one Linux host to another.

Content

Good to know: get started with containers by installing Docker on your Linux distro.

Table of Contents

Save Container Image from Source Host

Start by listing the available Docker containers running on your system. In my case, I want to export my Nginx Docker container to a new machine:

docker ps

Find the container that you want to copy over then stop the instance:

docker stop NAME_OF_INSTANCE

A Docker container is built out of a generic, initial image. Over time, you add your own changes to this base image. Processes running inside the container might also save their own data or make other changes. To preserve all of this, commit the current state of your container to a new image:

docker commit NAME_OF_INSTANCE mycontainerimage

Note that if the instance is currently running, this action will pause it while its contents are saved. If this is a problem, you can avoid this pause by entering docker commit -p=false NAME_OF_INSTANCE mycontainerimage instead. However, don’t do this unless absolutely necessary. The odds of creating an image with inconsistent/incomplete data increase in this case.

Now, save your newly committed Docker container image to an archive file:

docker save -o mycontainerimage.tar mycontainerimage

Use your preferred file transfer method and copy your .tar file to the host where you want to move your Docker container. For example, the following command transfers my Nginx Docker image using scp:

scp ./mycontainerimage.tar ramces@my.ip.address.here:/home/ramces/

Exporting a Docker Volume from Your Container

One of the downsides of saving a Docker image is that it doesn’t come with the Docker accessories you’ve set up alongside your container. This includes any network bind mounts and the volumes you’ve made to store your persistent data.

To properly export your data volume, first install Git on your local machine:

sudo apt install git

Run the following command to download the volume export script for Docker:

git clone https://github.com/ricardobranco777/docker-volumes.sh.git

Make sure that the export script has the right permission bits, then copy it to your machine’s “/usr/local/bin:”

sudo chmod +x ./docker-volumes.sh/docker-volumes.sh
sudo cp ./docker-volumes.sh/docker-volumes.sh /usr/local/bin/

Test whether your script is working properly, then extract all the associated volumes for your container:

docker-volumes.sh -h
docker-volumes.sh NAME_OF_INSTANCE save mycontainerimage-volume.tar

Send your newly archived Docker volume files to your remote machine:

scp ./mycontainerimage-volume.tar ramces@my.ip.address.here:/home/ramces/

Load Container Image on Destination Host

docker load -i ./mycontainerimage.tar

Use docker create to reinitialize your Docker container image with its original run flags from your source machine. For instance, my Nginx Docker container originally had port 80 mapped to my host machine’s port 8080:

docker create --name my-nginx-container -p 8080:80 mycontainerimage

Run your newly imported Docker container:

docker start my-nginx-container

Confirm that your imported image is working properly by listing all the active containers in the system:

docker ps

FYI: turn your Raspberry Pi into a capable portable photo gallery by installing Photoprism with Docker.

Importing a Docker Volume to Your Container

To import a .tar Docker volume file, first download Git on your new host:

sudo apt install git

Just like with your original system, download the docker-volume.sh helper script, set its permissions bits to “execute,” then copy it to your new machine’s “/usr/local/bin” directory.

Create a new Docker container using your exported image file:

docker create --name my-nginx-container -v myvol:/usr/share/nginx/html -p 8080:80 mycontainerimage

Run the docker-volume.sh script with your original .tar file to load it to your new system’s Docker daemon:

docker-volumes.sh my-nginx-container load mycontainerimage-volume.tar

Start your new Docker container by running the following command:

docker start my-nginx-container

Test if your container is loading your volume properly by looking at its internal config data:

docker inspect -f '{{ .Mounts }}' my-nginx-container

Transfer Image without Creating a File

Sometimes you may want to skip creating a mycontainerimage.tar.gz file. Maybe you don’t have enough disk space since the container has a lot of data in it. You can save, transfer, and load the image on the destination host in one command. After running the docker commit command discussed above, you can use this:

docker save mycontainerimage | ssh ramces@my.ip.address docker load

It should work from Windows, too, since it now has a built-in SSH client (PuTTY not necessary anymore).

Continue with the docker create command that applies to your situation.

Note: Make sure that you’ve properly mounted any Docker volume that was previously attached to your container before starting the imported image.

Lastly, start your newly imported Docker container by running docker start followed by your container’s name.

Using Docker Compose to Move an Entire Docker Deployment

With its Compose plugin, Docker makes it possible to build, configure, and run complex programs without worrying about the server’s underlying software stack. This, in turn, allows you to build reproducible application deployments across different Linux systems.

To start migrating your existing Docker setup to Docker Compose, first make sure that its plugin is currently in your system:

sudo apt install docker-compose-plugin docker-buildx-plugin

Create a new folder in your home directory for your Docker Compose installation:

mkdir ~/my-docker-compose && cd ~/my-docker-compose

Use your favorite text editor to create a “docker-compose.yml” file for your application:

nano ./docker-compose.yml

Paste the following block of code inside your Compose file, then tweak it to your specific needs:

version: '3'

volumes:
  myvol: # Replace with the name of your imported volume.

services:
  nginx:
    image: mycontainerimage # Replace with the name of your imported Docker image.
    ports:
      - "8080:80"
    volumes:
      - myvol:/usr/share/nginx/html # Replace "myvol" with the name of your mounted image.

Save your new Compose file, then run the following command to start it:

docker compose up -d

Lastly, test if your Compose deployment is working properly. In my case, I will test my Nginx Docker container by opening a web browser and navigate to “localhost:8080.”

Learning how to copy and move your Docker container to other Linux hosts is just one of the few tasks that you can do with your machine. Explore this wonderful world of self-hosting by installing a Minecraft server on Linux using Docker.

Image credit: Max Duzij via Unsplash. All alterations and screenshots by Ramces Red.

Subscribe to our newsletter!

Our latest tutorials delivered straight to your inbox

Sign up for all newsletters.
By signing up, you agree to our Privacy Policy and European users agree to the data transfer policy. We will not share your data and you can unsubscribe at any time. Subscribe

Ramces Red –
Staff Writer

Ramces is a technology writer that lived with computers all his life. A prolific reader and a student of Anthropology, he is an eccentric character that writes articles about Linux and anything *nix.