Where is the image downloaded by docker stored locally?

Docker Where is the downloaded image stored locally?

Docker (container) is one of the very popular open source projects in recent years. It provides a fast, flexible and portable application deployment method. Docker containers are somewhat similar to virtual machines, but have the advantages of smaller size, faster startup speed, and easier maintenance. Docker image is the basis of Docker container. It is a lightweight, portable packaging file that contains components such as code, running environment, libraries and dependencies, making it easier to deploy applications.

When using Docker, we need to download various images to deploy the required environment. These images may be downloaded from public image libraries or from private image libraries within the company. So where are these downloaded images stored locally?

Local Image Library

When we use Docker to download the image, the image will be stored locally in a place called the Local Registry. The local image library is the storage and management center for Docker images. It is a local repository automatically created after Docker is installed to store downloaded images. All downloaded images are stored in the local image library for subsequent deployment operations.

In Docker, you can use the docker images command to view all images that have been downloaded locally. Enter docker images in the terminal, and you will see an output similar to the following:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
nginx               latest              ae2feff98a0c        4 weeks ago         133MB
hello-world         latest              bf756fb1ae65        11 months ago       13.3kB

The output contains information about all downloaded images, including image name, image tag (Tag), image ID, and creation time. and size etc.

Local storage path

Of course, it is easy to find where the local mirror library is. If we have installed Docker, the local storage path defaults to the /var/lib/docker directory under Docker's data storage directory. Container and other Docker metadata and configuration files are stored in this directory.

We can view the location of the Docker data storage directory through the following methods:

1. Enter the command in the terminal or command line:

   docker info | grep -i 'root dir'

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2. Or view the files and directories in this directory through the following command:

   ls /var/lib/docker

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In the /var/lib/docker directory, there are many subdirectories, one of which is image. It is the directory where Docker caches images locally. We can also view the downloaded image files directly in this directory.

/var/lib/docker/image/overlay2/imagedb/content/sha256$ ls
00/00e2c30fcbefda162d7b0a8b3f3d1f13189b4967303b32f3b3ccc9956a3c6d43
01/8ff1c9d6bdcab994bd93b6f8cf58cfc93d150e5b328d50f8ca9b9be40d93ea5f
...

In this directory, you can see some subdirectories named with sha256 strings. These subdirectories contain the downloaded image files.

Of course, we can also change Docker’s data storage directory. For details, please refer to Docker’s official documentation.

Conclusion

To sum up, the image downloaded in Docker is actually stored in a local image library locally, and the default storage path of the local image library (of course the default path is also can be changed) is in the /var/lib/docker directory. Therefore, if you need to view or back up the downloaded image, you can do so through these methods.

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