Docker has become a cornerstone in the modern software development landscape. It empowers developers to package and run applications in a consistent and portable manner, irrespective of the underlying infrastructure. This guide serves as a gentle introduction to Docker, delving into the essential commands that will kickstart your journey into the world of containers.

1. Verifying Docker Installation:

The first step is to verify that Docker is installed on your system. Run the following command:

sudo docker --version

This command displays the installed Docker version.

2. Running the “Hello World” Application:

To experience the magic of Docker firsthand, let’s run the “hello-world” application:

sudo docker run hello-world

This command fetches the “hello-world” image from Docker Hub and executes it, displaying a simple message on your console.

3. Listing Running Containers:

Docker allows you to manage multiple containers simultaneously. To view a list of all running containers, use the following command:

sudo docker ps

This command displays a table with information about each running container, including its ID, image name, status, and ports.

4. Launching an Interactive Container:

One of Docker’s key features is the ability to run applications in an isolated environment. To experience this, let’s launch an interactive container based on the Ubuntu image:

sudo docker run -it ubuntu bash

This command not only starts the container but also provides you with a terminal inside the container, allowing you to execute commands and interact with the system as if it were a regular machine.

5. Searching for Images:

Docker Hub, a public registry, hosts a vast collection of images. You can search for images by name, description, or other criteria using the following command:

sudo docker search ubuntu

This command searches for images containing the keyword “ubuntu” and displays a list of relevant results.

6. Running a Command Inside a Container:

Often, you may want to run specific commands within a container. To achieve this, you can combine the run command with the -it flag and specify the desired command:

sudo docker run -it ubuntu bash
sudo apt-get update

This example updates the package list inside the Ubuntu container.

7. Diving Deeper with docker info:

For a comprehensive overview of your Docker environment, use the info command:

sudo docker info

This command provides detailed information about the Docker daemon, including its configuration, network settings, and storage options.

8. Exploring All Containers:

By default, docker ps only lists running containers. To view all containers, including those that have stopped, use the -a flag:

sudo docker ps
sudo docker ps -a

The first command displays only running containers, while the second command shows both running and stopped containers.

9. Alternative Listing Formats:

Docker provides various options for customizing the output of the docker ps command. The -l flag allows you to specify the desired format, such as JSON or table:

sudo docker container ls
sudo docker container ls -a

The container ls command is an alias for docker ps. The first command lists all running containers in a table format, while the second command, with the -a flag, lists all containers (running and stopped) in a table format.

10. Mastering Container Management:

Now that you’ve gained familiarity with basic commands, let’s delve into container management, covering operations such as starting, stopping, removing, and restarting containers.

11. Initiating a Container:

To start a container, use the run command with the -it flag for an interactive session:

sudo docker run -it centos bash

This command starts a container based on the CentOS image and provides you with a terminal inside the container.

12. Halting a Container:

To stop a running container, use the stop command:

sudo docker stop <container_id>

Replace <container_id> with the ID of the container you want to stop.

13. Removing a Container:

Once you’re done with a container, you can remove it using the rm command:

sudo docker rm <container_id>

This command removes the specified container from your system.

14. Restarting a Container:

To restart a stopped container, use the restart command:

sudo docker restart <container_id>

This command restarts.

15.Running a CentOS Container:

sudo docker container run -it centos:7 bash

sudo: Grants root privileges for container operations. docker container run: Creates a new Docker container. -it: Allocates a pseudo-terminal (interactive shell) for interacting with the container. centos:7: Specifies the Docker image to use (CentOS version 7). bash: Launches a Bash shell within the container.

16.System Update:

sudo yum -y update

sudo: Again, for root privileges (package management often requires them). yum: The package manager for RPM-based systems like CentOS. -y: Automatically confirms any prompts during the update process (use with caution in production environments). update: Updates system packages to their latest versions.

17.Listing Directory Contents:

ls -l

ls: Lists files and directories. -l: Provides detailed information in long format (including permissions, owner, group, size, and timestamps).

18.Creating a File:

echo "we are here" >

echo: Prints text to the terminal or a file. “we are here”: The text to be written.

: Redirects the output to a file (creates in this case)

19.Verifying File Creation:

ls -l

Lists the directory contents again, showing the newly created

20.Viewing File Contents:


cat: Displays the contents of a file. The file to display.

21.Exiting the Container:


Terminates the interactive shell session within the container.

22.Listing Running Containers:

sudo docker ps

sudo: For root privileges. docker ps: Lists currently running Docker containers.

23.Listing All Containers (Including Stopped Ones):

sudo docker ps -a

-a: Shows all containers, regardless of their running state.

24.Running Another Container:

sudo docker container run -it centos:7 bash

Re-runs the container creation command from step 1.

25.Exiting the Second Container:


Terminates the shell session within the second container

26.Listing All Containers Again:

sudo docker ps -a

Verifies both containers are listed.

27.Starting a Stopped Container:

sudo docker container start [containerid]

start: Attempts to start a stopped container. [containerid]: Replace this with the actual ID of the container you want to start (obtainable from docker ps -a).

28.Verifying the Started Container:

sudo docker ps

Checks if the previously stopped container is now listed as running.

29. Inspecting Processes Within a Container:

sudo docker container exec [containerid] ps -ef

exec: Executes a command within a running container. [containerid]: The ID of the container to access. ps -ef: Lists all processes running inside the container (similar to ps -aux on Linux).

30.Interactive Access to the Container:

sudo docker container exec -it [containerid] bash

-it: Allocates a pseudo-terminal for interactive interaction. Provides access to the Bash shell within the specified container, allowing you to execute further commands.

31.Verifying File Creation (Inside the Container):

ls -l

Lists directory contents, showing

32.Viewing File Contents (Inside the Container):


Displays the contents of created earlier.


Replace [containerid] with the actual container ID in steps 13, 15, and 16. Use docker ps -a to view all containers, including stopped ones.