An Enthusiastic Programmer

Manage your Images, Containers

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After you build and run your image successfully, then you need to manage them. Docker provides a full, complete manage command that fits for you. This article divides into three main parts.

  1. Image management.
  2. Container management.
  3. Interaction.

This blog continues from the previous episode, if you are unfamiliar, take a review look at build and run your image.

Image Management

It’s important to manage your Images in Docker. Docker provides a set of built-in commands that assistant your management on Images. The following contents list the almost highly touched commands during Images management. You can run the docker image --help or docker --help to explore more information.

List images

docker image ls
docker images

Remove an image

docker image rm <myimage>
docker rmi <myimage>

Remove an image by force

docker image --force rm <myimage>
docker rmi --force <myimage>

Show an image history

docker image history <myimage>
docker history <myimage>

copy an image from another Image

docker image tag <source_image> <new_image>

Remove unused images

docker image prune

Pull an image or a repository from a gegistry

docker image pull <image_registry>
docker pull <image_registry>

Push an image or a repository to a registry

docker image push <myimage>
docker push <myimage>

Load an image from a tar archive or STDIN

docker image load -i <tarfile>
docker load -i <tarfile>

Save one or more images to a tar arhchive(stream to STDOUT by default)

docker image save -o <output_tar_file>
docker save -o <output_tar_file>

Container Management

You’ve known how to manage your Images in the command line, where you can also manage your container. Here, I am going to show you the basic commands that you may need. You can run the docker container --help or docker --help to explore more information.

List all running containers

docker container ls
docker ps

List all running and stopped containers

docker container ls -a
docker ps -a

List all stopped containers

docker ps --filter "status=exited"
docker ps -f "status=exited"

Stop one or more running containers

docker container stop <mycontainer>
docker stop <mycontainer>

Start one or more stopped containers

docker container start <mycontainer>
docker start <mycontainer>

Remove a container

docker container rm <mycontainer>
docker rm <mycontainer>

Remove a container by force

docker container rm --force <mycontainer>
docker rm --force <mycontainer>

Remove all stopped containers

docker container prune

Copy files/folders between a container and the local filesystem

docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH
docker cp [OPTIONS] SRC_PATH CONTAINER:DEST_PATH

The former copies the container to the host, and the later copies the host to the container.

Interaction

Attach local standard input, output, and error streams to a running container

docker attach <mycontainer>

Get inside a container’s filesystem on a running container

docker exec -it <mycontainer> bash

Get inside an image’s filesystem

docker run -it --entrypoint /bin/bash <imageid>

Docker Attach and Docker Exec both can let you connect to your container, but the Docker Attach isn’t really the same thing as SSH. For example, if your container is running a webserver, the Docker Attach will probably connect you to the stdout of the webserver process. The Docker Exec command can let you get inside a running container, it didn’t like the Docker Attach, Docker Exec will let you get inside the really private filesystem. The docker run -it --entrypoint /bin/bash <imageid> base on an image, so you can inspect an image’s filesystem, without running it as a container first. If you want to exit the interactive window, input the exit command.

If you execute the above bin/bash command, you may encounter a crash error. Just as the fallowing:

$ # try to get inside on a container
$ docker exec -it <mycontainer> bash
rpc error: code = 2 desc = oci runtime error: exec failed: container_linux.go:247: starting container process caused "exec: \"bash\": executable file not found in $PATH"
$ 
$ # try to get inside on an image
$ docker run -it --entrypoint /bin/bash <myimage>
Error response from daemon: OCI runtime create failed: container_linux.go:349: starting container process caused "exec: \"/bin/bash\": stat /bin/bash: no such file or directory": unknown.

You have these errors because your container/image doesn’t have a bash command installed. However, there are still have other solutions for these problems, if your bash hasn’t installed, you should use /bin/sh instead.

$ # try to get inside on a container
$ docker exec -it <mycontainer> /bin/sh
$ 
$ # try to get inside on an image
$ docker run -it --entrypoint /bin/sh <myimage>

Or more visualization, you can view your containers filesystem without really get inside it.

$ docker exec -ti <mycontainer> ls /etc

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