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

Running 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’ll return to your OS shell.

You’ll then be running in the instance of the CentOS system on the Ubuntu server.

Listing of Containers

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

docker ps

Syntax

docker ps

Options

None

Return Value

The output will show the currently running containers.

Example

sudo docker ps

Output

When we run the above command, it’ll produce the subsequent result −

Let’s see some more variations of the docker ps command.

docker ps -a

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

Syntax

docker ps -a

Options

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

Return Value

The output will show all containers.

Example

sudo docker ps -a

Output

When we run the above command, it’ll produce the subsequent result −

docker history

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

Syntax

docker history ImageID

Options

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

Return Value

The output will show all the commands run against that image.

Example

sudo docker history centos

The above command will show all the commands that were run against the centos image.

Output

When we run the above command, it’ll produce the subsequent result −

Docker – Working with Containers

In this chapter, we will explore in detail what we can do with containers.

docker top

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

Syntax

docker top ContainerID

Options

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

Return Value

The output will show the top-level processes within a container.

Example

sudo docker top 9f215ed0b0d3

The above command will show the top-level processes within a container.

Output

When we run the above command, it’ll produce the subsequent result −

docker stop

This command is employed to stop a running container.

Syntax

docker stop ContainerID

Options

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

Return Value

The output will give the ID of the stopped container.

Example

sudo docker stop 9f215ed0b0d3

The above command will stop the Docker container 9f215ed0b0d3.

Output

When we run the above command, it’ll produce the subsequent result −

docker rm

This command is employed to delete a container.

Syntax

docker rm ContainerID

Options

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

Return Value

The output will give the ID of the removed container.

Example

sudo docker rm 9f215ed0b0d3

The above command will remove the Docker container 9f215ed0b0d3.

Output

When we run the above command, it’ll produce the subsequent result −

docker stats

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

Syntax

docker stats ContainerID

Options

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.

Example

sudo docker stats 9f215ed0b0d3

The above command will provide CPU and memory utilization of the Container 9f215ed0b0d3.

Output

When we run the above command, it’ll produce the subsequent result −

docker attach

This command is employed to attach to a running container.

Syntax

docker attach ContainerID

Options

ContainerID − This is the Container ID to which you need to attach.

Return Value

None

Example

sudo docker attach 07b0b6f434fe

The above command will attach to the Docker container 07b0b6f434fe.

Output

When we run the above command, it’ll produce the subsequent result −

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 employed to pause the processes in a running container.

Syntax

docker pause ContainerID

Options

ContainerID − This is the Container ID to which you need to pause the processes in the container.

Return Value

The ContainerID of the paemployed container.

Example

sudo docker pause 07b0b6f434fe

The above command will pause the processes in a running container 07b0b6f434fe.

Output

When we run the above command, it’ll produce the subsequent result −

docker unpause

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

Syntax

docker unpause ContainerID

Options

ContainerID − This is the Container ID to which you need to unpause the processes in the container.

Return Value

The ContainerID of the running container.

Example

sudo docker unpause 07b0b6f434fe

The above command will unpause the processes in a running container: 07b0b6f434fe

Output

When we run the above command, it’ll produce the subsequent result −

docker kill

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

Syntax

docker kill ContainerID

Options

ContainerID − This is the Container ID to which you need to kill the processes in the container.

Return Value

The ContainerID of the running container.

Example

sudo docker kill 07b0b6f434fe

The above command will kill the processes in the running container 07b0b6f434fe.

Output

When we run the above command, it’ll produce the subsequent result −

Docker – Container Lifecycle

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

Initially, the Docker container will be in the created
Then the Docker container goes into the running state when the Docker run command is employed.
The Docker kill command is employed to kill an existing Docker container.
The Docker pause command is employed to pause an existing Docker container.
The Docker stop command is employed to pause an existing Docker container.
The Docker run command is employed to put a container back from a stopped state to a running

Docker – Architecture

The subsequent image shows the standard and traditional architecture of virtualization.

The server is the physical server that is employed to host multiple virtual machines.
The Host OS is the base machine such as Linux or Windows.
The Hypervisor is either VMWare or Windows Hyper V that is employed to host virtual machines.
You would then install multiple operating systems as virtual machines on top of the existing hypervisor as Guest OS.
You would then host your applications on top of each Guest OS.

The subsequent image shows the new generation of virtualization that is enabled via Dockers. Let’s have a look at the various layers.

The server is the physical server that is employed to host multiple virtual machines. So this layer remains the equivalent.
The Host OS is the base machine such as Linux or Windows. So, this layer remains the equivalent.
Now comes the new generation which is the Docker engine. This is employed to run the operating system which earlier employed to be virtual machines as Docker containers.
All of the Apps now run as Docker containers.

The clear advantage in this architecture is that you don’t need to have extra hardware for Guest OS. Everything works as Docker containers.

So, this brings us to the end of blog. This Tecklearn ‘How to work with Containers in Docker’ blog helps you with commonly asked questions if you are looking out for a job in DevOps. If you wish to learn Docker and build a career in DevOps domain, then check out our interactive, Containerization using Docker Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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Containerization using Docker Training

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What you will Learn in this Course?

Introduction to DevOps

What is Software Development
Software Development Life Cycle
Why DevOps?
What is DevOps?
DevOps Lifecycle
DevOps Tools
Benefits of DevOps
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DevOps Implementation

Containerization using Docker – Part 1

Introduction to Docker
Understanding Docker Lifecycle
Docker Architecture
Components of Docker Ecosystem
Common Docker Operations
Committing changes in a Container
Hands On

Containerization using Docker – Part 2

Building Custom Docker Images
Docker Image
Introduction to Docker Swarm
Deploying a 2-Node Cluster using Docker Swarm
Hands on

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