How to Save Docker Images as a TAR File

Introduction

Docker images package applications and their dependencies into a portable format. For example, you can save a Docker image as a file for backup, storage, or transfer between different environments.

Docker provides the docker save command to create a TAR archive from a Docker image. As a result, you can store the TAR file for future use.

In this guide, we will explain how to save a Docker image as a TAR file and verify the generated archive.

Prerequisites

Before you begin, make sure you have the following:

• Docker is installed on the server.
• The Docker service is running.
• You have the required permissions to run Docker commands.
• The Docker image that you want to save is available on the server.
• Make sure you have enough disk space to create the TAR file.

IMPLEMENTATION

Step 1: Identify the Docker Image

First, list the available Docker images with the following command:

docker images

Example:

Step 2: Save the Docker Image as a TAR File

Next, use the docker save command to create a TAR file from the Docker image:

For example, the following command saves the alpine:latest image as mynewimage.tar

docker save -o mynewimage.tar alpine:latest

Here:

• docker save creates an archive of the Docker image.
• -o mynewimage.tar specifies the name of the output TAR file.
• alpine:latest Specifies the Docker image that you want to save.

Step 3: Verify the TAR File

After that, check whether Docker created the TAR file successfully:

ls -lh mynewimage.tar

Step 4: Compress the TAR File (Optional)

If the TAR file is large, you can compress it with gzip to reduce its size:

gzip mynewimage.tar

This creates:

mynewimage.tar.gz

Alternatively, you can save and compress the Docker image directly:

docker save alpine:latest | gzip > myapp.tar.gz  

Conclusion

Saving a Docker image as a TAR file provides a simple way to create a portable copy of the image. The docker save command creates the TAR archive, which you can store as a backup or use for other Docker image management tasks.

By following these steps, you can easily save a Docker image as a TAR file and verify the generated archive.

FAQ

Can we compress a Docker TAR file?

Yes. You can use gzip to compress the TAR file and create a .tar.gz file.

How can I restore a Docker image from a TAR file?

You can use the docker load command to import the Docker image from the TAR file. For example:

docker load -i mynewimage.tar

Can we save multiple Docker images in one TAR file?

Yes. The docker save command allows you to save multiple Docker images into a single TAR file.

docker save -o images.tar alpine:latest nginx:latest

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