Let's talk about where Docker images are stored

Docker is a popular containerization technology often used to build, deploy and manage applications. Unlike traditional virtualization technology, Docker containers can start faster, be more lightweight, and can be used across platforms. Mirroring is an important concept when using Docker. So where are Docker images stored?

Docker image is a read-only template that contains information such as operating system, application and library files required to build a container. Docker can download and use ready-made images from Docker Hub or other Docker Registries, or you can build images yourself through Dockerfile.

When we use Docker to download or build an image, the image will be saved on our local machine. Specifically, Docker images are stored in the image warehouse of the Docker daemon. This warehouse is located in the /var/lib/docker directory of the local machine by default.

In the /var/lib/docker directory, there are three important subdirectories:

• aufs: used to store images and container data based on AUFS (Another Union File System) .
• containers: used to store container metadata, container logs and other information.
• images: Used to store the relationships and metadata between images. Each image has its own subdirectory, containing the metadata information and hierarchical data of the image.

In the /var/lib/docker directory, there are many other subdirectories and files, which are all related to the normal operation of the Docker daemon.

In addition to the local image warehouse, Docker also supports the use of remote image warehouses. If we need to use the public Docker image warehouse, we can download the image through the following command:

docker pull image_name:tag

where image_name is the name of the image and tag is the label of the image. If tag is omitted, the latest tag is used by default.

If we need to use our own private Docker image warehouse, we can use the following command to upload the image:

docker push image_name:tag

It should be noted that when uploading the image, you need to log in to the private warehouse first, which can be achieved through the following command ：

docker login registry_server_address

Among them, registry_server_address is the address of the private warehouse.

In short, the Docker image is stored in the local image warehouse of the Docker daemon. Whether you download public images or build your own images, they are all stored and managed based on the local image warehouse. If we need to use a remote image warehouse, we can quickly download and upload images through the commands provided by Docker.

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