Docker

What happens when we run the “docker container run” command?

There is always more to anything out there in the world, and same is the case with “docker container run” command.

From the screenshot below, look closely we are going to take the this as an example command.

Docker container run command
Docker container run command

The following happens during the command’s execution:

Step 1: First of all, the docker is going to look for the availability of the image “locally“.

Unable to find the image locally
Unable to find the image locally

Step 2: If the image is not found “locally“, then it checks for the image remotely, and by default, it checks on the “hub.docker.com“.

Moreover, in our case it does not find the image locally, so it pulled the “nginx:latest” image from “library/nginx” which is “nginx’s” official repository on “hub.docker.com“.

Pulling from remote repository docker hub
Pulling from remote repository docker hub

Step 3: After pulling the image, it also shows the “Digest” of the image, for the reference check below.

Digest of a docker image
Digest of a docker image

To learn more about docker, follow -> Learn Docker

Step 4: Lastly, after pulling the image remotely, it is going to make it run and return the “Container ID” on the terminal/console, for reference check below.

Status and Container ID
Status and Container ID

Conclusion

From this post, we have learned many things, one more thing to note here is that when the image is executed, what actually happens is that a layer is added on the top of recently pulled image, which is considered as an instance or container.

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