7. Docker Container

Docker Container 

       Containers are instances of Docker images that can be run using the Docker run command. The basic purpose of Docker is to run containers. Let’s discuss how to work with containers.

Run a Container-

Running of containers is managed with the Docker run command. To run a container in an interactive mode, first launch the Docker container.

    #sudo docker run –it centos /bin/bash

Then hit Crtl+p and you will return to your OS shell.

Listing of Containers-

One can list all of the containers on the machine via the docker ps command. This command is used to return the currently running containers.

#docker ps

docker ps -a-

This command is used to list all of the containers on the system

#docker ps -a

  ─a – It tells the docker ps command to list all of the containers on the system.

docker history-

With this command, you can see all the commands that were run with an image via a container.

#docker history ImageID

ImageID – This is the Image ID for which you want to see all the commands that were run against it.

docker top-

With this command, you can see the top processes within a container.

#docker top ContainerID

ContainerID – This is the Container ID for which you want to see the top processes

docker stop-

This command is used to stop a running container.

#docker stop ContainerID

ContainerID – This is the Container ID which needs to be stopped.

docker rm-

This command is used to delete a container.

#docker rm ContainerID

ContainerID – This is the Container ID which needs to be removed.

Return Value

The output will give the ID of the removed container.

docker stats-

This command is used to provide the statistics of a running container.

#docker stats ContainerID

ContainerID – This is the Container ID for which the stats need to be provided.

Return Value

The output will show the CPU and Memory utilization of the Container.

docker attach-

This command is used to attach to a running container.

#docker attach ContainerID

Once you have attached to the Docker container, you can run the above command to see the process utilization in that Docker container.

docker pause

This command is used to pause the processes in a running container.

#docker pause ContainerID

docker unpause-

This command is used to unpause the processes in a running container.

#docker unpause ContainerID

The Docker pause command is used to pause an existing Docker container

docker kill-

This command is used to kill the processes in a running container.

#docker kill ContainerID

Docker – Container Lifecycle-

The following illustration explains the entire lifecycle of a Docker container.

             

                 Initially, the Docker container will be in the created state.

             Then the Docker container goes into the running state when the Docker      run command is used.

            The Docker kill command is used to kill an existing Docker container.

            The Docker stop command is used to pause an existing Docker container. 

      The Docker run command is used to put a container back from a stopped state to a running state