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What this article shares with you is about the relationship between docker images and containers. The editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

What is the relationship between the docker image and the container? A container is an instance of an image. Describe the image first, and then create the container, so there can be multiple containers. Mirroring is a read-only file system that is shared locally, mainly through signatures, similar to the De-dup technology in storage.

Each container you run adds a writable layer to the image, but this layer does not change the image itself, which is why sometimes you start multiple containers with the same image, and the contents remain the same. If you want to persist the writable layer, use the commit command to write the writeable layer to disk, that is, to generate a new image.

In general, the image is a file and the container is a process. The container is created based on the image, that is, the process in the container depends on the files in the image, including executable files, dependent software, library files, configuration files, and so on.

Assuming that you need to run nginx (web server) in a docker container, the first step is to download the nginx image:

Sudo docker pull nginx

After downloading nginx image, you can view Docker image:

Sudo docker imagesREPOSITORY TAG IMAGE ID CREATED SIZEnginx latest 0d409d33b27e 2 weeks ago 182.7 MB

In fact, the nginx image is not a single file, but has a hierarchical structure:

Sudo docker history nginxIMAGE CREATED CREATED BY SIZE COMMENT0d409d33b27e 2 weeks ago / bin/sh-c # (nop) CMD ["nginx"- g"daemon o 0 B 2 weeks ago / bin/sh-c # (nop) EXPOSE 443/tcp 80/tcp 0 B 2 weeks ago / bin/sh-c ln-sf / dev/stdout / var/log/nginx/ 0 B 2 weeks ago / bin/sh-c apt-key adv-- keyserver hkp://pgp. 57.67 MB 2 weeks ago / bin/sh-c # (nop) ENV NGINX_VERSION=1.11.1-1 ~ 0 B 3 weeks ago / bin/sh-c # (nop) MAINTAINER NGINX Docker Mai 0 B 3 weeks ago / bin/sh-c # (nop) CMD ["/ bin/bash"] 0 B 3 weeks ago / bin/sh-c # (nop) ADD file:5d8521419ad6cfb695 125.1 MB

You can see that the nginix image has a total of 8 layers, of which the first layer is 125.1MB, the fifth layer is 57.67MB, and the size of other layers can be ignored.

Run nginx in the Docker container:

Sudo docker run-itd\-p 80:80\-name=nginx\ nginx

View nginx Container

Sudo docker psCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES263e88fc53d3 nginx "nginx-g'daemon off" 3 seconds ago Up 2 seconds 0.0.0.0 daemon off 80-> 80/tcp, 443/tcp nginx

You can see that the nginx container runs successfully.

The above is the relationship between docker images and containers. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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