How to save all Docker images and copy to another machine?

Introduction

Docker images are the building blocks of containerized applications. They are lightweight, portable and can be easily shared between different machines. In this article, we'll take a look at how to save all Docker images on one machine and transfer them to another machine.

Method 1: Using docker save and docker load

One way to save and transfer Docker images is by using the docker save and docker load commands. The docker save command allows you to save one or more images to a tar archive, which can then be transferred to another machine. The docker load command allows you to load the images from the tar archive onto the other machine. Here are the steps to save and transfer all Docker images using docker save and docker load −

• Use the docker images command to list all images on the machine.

docker images 

• Use the docker save command to save each image to a tar file.

docker save image-name > image-name.tar 

• Copy the tar files to the other machine using scp, rsync or other methods.

scp image-name.tar user@remote-machine:~/ 

• Use the docker load command to load the images onto the other machine.

docker load < image-name.tar 

For example, to save and load all the images, you can use the following command −

docker images -q | xargs -I {} docker save {} > {}.tar 

This command will save all images to different tar files and you can then transfer all the tar files together.

On the other machine, you can use the following command to load all the images −

find . -name "*.tar" -exec docker load < {} \; 

This command will look for all tar files in the current directory and load them into Docker.

Method 2: Using docker export and docker import

Another way to save and transfer Docker images is by using the docker export and docker import commands. The docker export command allows you to export a container's filesystem as a tar archive, which can then be transferred to another machine. The docker import command allows you to import the filesystem from the tar archive into a new Docker image. Here are the steps to save and transfer all Docker images using docker export and docker import −

• Use the docker ps -a command to list all containers on the machine.

docker ps -a 

• Use the docker export command to export each container to a tar file.

docker export container-name > container-name.tar 

• Copy the tar files to the other machine using scp, rsync or other methods.

scp container-name.tar user@remote-machine:~/ 

• Use the docker import command to import the images onto the other machine.

docker import container-name.tar image-name 

Method 3: Using a container registry

A container registry is a service that allows you to store and distribute Docker images. You can use a container registry to save all Docker images on one machine and pull them on another machine. Here are the steps to save and transfer all Docker images using a container registry −

• Use the docker login command to log in to a registry.

docker login registry-name 

• Use the docker tag command to tag each image with the registry URL.

docker tag image-name registry-name/image-name 

• Use the docker push command to push the images to the registry.

docker push registry-name/image-name 

• On the other machine, use the docker pull command to pull the images from the registry.

docker pull registry-name/image-name 

Benefits of saving and copying Docker images to another machine

Saving and copying Docker images to another machine provides several benefits for managing containerized applications −

Benefits	Description
Disaster recovery	Having a backup copy of the images on another machine allows you to quickly restore your application in case of a disaster or failure of the primary machine.
Centralized storage	Using a container registry allows you to store the images in a centralized location, making it easy to access, share and distribute the images across teams.
Scalability	Having a backup copy of the images allows you to quickly scale up or down your application by spinning up new instances of the containers on different machines.
Efficient deployment	Copying images to another machine allows you to deploy your application in different environments without the need to rebuild the images.
Easy testing	Copying images to another machine allows you to easily test your application on different hardware and software configurations.
Reducing the size of the container	By copying the images to another machine you can make a lightweight container, which will have less space and resource consumption.

Overall, saving and copying Docker images to another machine is an important aspect of managing containerized applications, providing a way to ensure availability, scalability and efficient deployment of applications

Best practices

When saving and transferring Docker images, it's important to ensure the integrity of the images during the transfer process, as well as to keep track of the versions of images. It is also good practice to compress the images before transferring them and test the process before deploying them to production. Additionally, it's a good idea to use a container registry service as they provide a central place to store and distribute images and automate the process of saving and transferring Docker images.

Conclusion

Saving and transferring Docker images is an important aspect of managing containerized applications. By understanding the different methods available, such as using docker save and docker load, docker export and docker import, or using a container registry, you can effectively save and transfer Docker images between different machines. Each method has its use cases and behaviours, so it's important to choose the one that best fits your needs. Remember to follow best practices like ensuring the integrity of the images during the transfer process, keeping track of image versions, compressing images before the transfer, testing the process before deploying to production, and using a container registry service.