Load a Docker Image From a Tar File

1. Overview

While working on Docker, we can save Docker images as a single tar file that can be easily shared, moved, or stored. This tar file contains the entire image which makes it portable to easily move the image to another system, share it with others, or store it for future use. Later, we can load these images from the tar file back into Docker to ensure smooth portability across various environments.

In this tutorial, we’ll learn how to save Docker images into tar files and load them back in.

2. Save the Docker Image as a Tar File

First, we can display the available Docker images on the system using the docker images command:

$ docker images
REPOSITORY    TAG       IMAGE ID       CREATED         SIZE
nginx         latest    447a8665cc1d   7 weeks ago     273MB
ubuntu        latest    8a37d68f4f73   2 months ago    117MB
redis         latest    878983f8f504   2 months ago    174MB
mysql         latest    d8df06984890   2 months ago    802MB
hello-world   latest    53cc4d415d83   17 months ago   24.4kB

Let’s now use the docker save command to save the desired Docker image into a tarball called my-nginx.tar:

$ docker save nginx -o my-nginx.tar

Alternatively, we can use file redirection to achieve the same:

$ docker save nginx > my-nginx.tar

For verification, let’s list the current directory’s content to check the my-nginx.tar file:

$ ls C:\Users\thinkpad

    Directory: C:\Users\thinkpad

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----         9/22/2024   6:51 PM                .docker
d-r---         9/21/2024   8:54 PM                Desktop
-a----          9/2/2024  12:35 AM       71040000 my-nginx.tar

Hence, we successfully created the my-nginx.tar file. We can now transfer it to another system or save it locally for future use and load it when needed.

Having exported the image to our filesystem, let’s now remove the nginx image from Docker:

$ docker rmi nginx   
Untagged: nginx:latest
Deleted: sha256:447a8665cc1dab95b1ca778e162215839ccbb9189104c79d7ec3a81e14577add

If we list the docker images now, we’ll see that the nginx image has been removed:

$ docker images   
REPOSITORY    TAG       IMAGE ID       CREATED         SIZE
ubuntu        latest    8a37d68f4f73   2 months ago    117MB
redis         latest    878983f8f504   2 months ago    174MB
mysql         latest    d8df06984890   2 months ago    802MB
hello-world   latest    53cc4d415d83   17 months ago   24.4kB

3. Load the Docker Image from a Tar File

To load our Docker image tarball back into Docker, we use docker load command along with the -i option to specify the path to the file:

$ docker load -i my-nginx.tar
Loaded image: nginx:latest

Alternatively, we can also use file redirection to achieve the same:

$ docker load < my-nginx.tar
Loaded image: nginx:latest

At this point, we’ve imported the Docker image stored in the my-nginx.tar file back into the local Docker environment.

4. Verify the Loaded Docker Image

Once we load the image, we can verify it by listing the Docker images:

$ docker images
REPOSITORY    TAG       IMAGE ID       CREATED         SIZE
nginx         latest    447a8665cc1d   7 weeks ago     273MB
ubuntu        latest    8a37d68f4f73   2 months ago    117MB
redis         latest    878983f8f504   2 months ago    174MB
mysql         latest    d8df06984890   2 months ago    802MB
hello-world   latest    53cc4d415d83   17 months ago   24.4kB

We can see from the output that the nginx image is again available. It’s perhaps of interest that all the properties remain the same, including the created time. This is because Docker preserved and now restored all the image’s metadata, including the image creation date, image size, and so on.

Now that we have the image loaded, it’s safe to delete my-nginx.tar from our filesystem.

5. Conclusion

In this article, we explained the method to load a Docker image from a tar file. We first saved an image into a tar file using the docker save command. Then, we used the docker load command to load the Docker image from the tar file.

Ultimately, we can use this method to save any Docker image into a tar file for offline distribution, backups, or secure transfers between environments, and load it from the tar file when needed.