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Docker Tutorial: Master Docker from Scratch

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Docker Tutorial

๐Ÿ’– Introduction

This tutorial is designed for complete beginners to advanced users who want to learn Docker from scratch. It covers everything you need to know about Docker, from installation and configuration to creating and running containers, images, and volumes. It also explains the concepts and benefits of Docker, such as port mapping, networking, security, and compose. By the end of this tutorial, you will have no doubts about how to use Docker effectively and efficiently.

This tutorial is also full of practical examples and projects that will help you apply what you learn and gain hands-on experience with Docker. You will learn how to create a Python Flask app, a Node.js app, a Postgresql database, and a Mongo Express web interface using Docker. You will also learn how to build, run, stop, delete, and push your Docker images and containers.

I have created this tutorial with the aim of helping you learn Docker in a fun and easy way. If you appreciate his effort and find this tutorial useful, please give it a star (โญ) on GitHub and share it with your friends.

So what are you waiting for? Let's dive into the world of Docker and see what it can do for you!

Why should I use Docker ๐Ÿณ ?

Have you ever faced this problem? ๐Ÿ˜ฑ

Your code works fine on your dev environment, but when you publish it on the server, it breaks and gives you errors. You don't know why ,and you have to fix it quickly. You find out that you forgot to install a dependency or you used a different version of a tool.

If yes, then you need Docker! ๐Ÿ™Œ

Docker is a tool that lets you create and run containers. Containers are like boxes that have everything your app needs to run. They have the same files, programs, and settings on any environment. You can use the same container on your dev environment, your server, or any other computer. ๐Ÿ“ฆ

Using Docker will make your life easier because: ๐Ÿ˜Š

  • You won't have to worry about missing or mismatched dependencies on your server. Your container will have them all.
  • You won't have to install or configure anything on your dev environment. You can just use a container that has everything ready for you.
  • You can use containers for old or new projects. You can keep the dependencies that you need without affecting other projects or systems.
  • You can use containers to run your app on the cloud. You can also use tools like Docker Swarm or Kubernetes to manage multiple containers.

Docker is awesome and you should try it! ๐Ÿš€

Then what is Docker? ๐Ÿณ

Docker is a software platform that lets you run applications inside containers. Think of containers like virtual machines, but lighter and more efficient! ๐Ÿš€

So we use docker for :

  • Simplifies application deployment: Package your application and all its dependencies into a container that can run on any machine with Docker installed. ๐Ÿ“ฆ
  • Increases portability: Move Docker containers easily from one environment to another, like from a developer's laptop to a production server. ๐Ÿšš
  • Improves scalability: Quickly spin up multiple instances of your application to handle increased traffic. ๐Ÿ”

How does Docker work? ๐Ÿ”ง

Docker creates containers, which are isolated environments with their own filesystem, network, and processes. Each container runs a specific application along with its dependencies. ๐Ÿ“

To create a container, you first need to create a Docker image, which is a snapshot of your application and its dependencies. You can create an image by writing a Dockerfile, a script that specifies the instructions for building the image. ๐Ÿ“œ

Once you have an image, you can use it to create a container by running the docker run command. This starts a new container based on the image and runs the application inside it. ๐Ÿƒโ€โ™‚๏ธ

Example of Docker in action ๐Ÿ’ป

Let's say you have a web application that uses Node.js and MongoDB. Normally, you would need to install Node.js and MongoDB on your server and configure them to work together. With Docker, you can create two separate containers, one for Node.js and one for MongoDB, and run them on the same server

To do this, you would create two Docker images: one for the Node.js application and one for the MongoDB database. Then you would use the docker run command to start both containers, making sure to link them together so that the Node.js container can communicate with the MongoDB container.

By using Docker, you can simplify the deployment of your web application, make it more portable, and improve its scalability.

What is difference between Docker and Virtual Machine(VM)? ๐Ÿค”

โ— What is VM?

VM stands for virtual machine. A virtual machine is also like a mini-computer that runs on your main computer. But unlike a container, a virtual machine has its own operating system. This means that it can run any kind of application, regardless of the operating system of your main computer.

The advantage of using virtual machines is that they are very secure and isolated. They don't share anything with your main computer or with other virtual machines. If something goes wrong with one virtual machine, it won't affect the others. You can also run different operating systems on different virtual machines.

โ— What is Docker?

Docker is a tool that lets you create and run containers. Containers are like virtual machines, but they don't have their own operating system. They only have the files, programs, and settings that they need to run their application. This makes them very efficient and fast.

Docker doesn't have kernel-level virtualization like virtual machines do. Instead, it uses a container engine to create containers. This makes Docker much lighter and faster than virtual machines.

โ— How do they differ?

The main difference between docker and vm is how they use the resources of your main computer. Docker containers share the same operating system as your main computer. They only use the software that they need to run their application. This makes them very efficient and fast.

Virtual machines don't share anything with your main computer. They have their own operating system and hardware resources. This makes them more independent and secure, but also more heavy and slow.

Here is a table that summarizes some of the key differences between docker and vm:

Topic Docker VM
Operating system Shared Separate
Performance Fast Slow
Portability Easy Hard
Security Low High

How to install Docker ๐Ÿณ

  1. To get started, open this website: https://docs.docker.com/ and click on the Download and Install button. Then select the Docker Desktop for Windows or Docker Desktop for Mac or Docker Desktop for Linux button depending on your operating system. This will take you to the download page. ๐Ÿ–ฑ๏ธ
  2. Follow the instructions to install Docker Desktop for your operating system. You may need to restart your computer after the installation. ๐Ÿ”„
  3. Once you have installed Docker Desktop, you will see an interface like this: ๐Ÿ–ฅ๏ธ

image

  1. Now you can sign in to your Docker account or create a new one if you don't have one already. ๐Ÿ”‘
  2. On the interface, you will notice three sections: Containers, Images and Volumes. These are the main components of Docker that you need to know about. ๐Ÿ“ฆ

Containers , Images and Volumes ๐Ÿ“ฆ

  • Containers are like boxes that you can put things in. Each box has its own things that are separate from the other boxes. You can open and close a box without affecting the other boxes or the room. Containers are like boxes that have their own files, programs, and settings that are separate from the other containers or the computer. You can create and delete containers without affecting the other containers or the computer. Containers are fast and easy to use because they use the same system as the computer and do not need to start a whole new system like virtual machines do.
  • Images are like recipes for making containers. They tell you what ingredients and steps you need to make a container. You can use an existing recipe from a public place like Docker Hub, or you can write your own recipe using a Dockerfile. Recipes do not change once they are written. You can use the same recipe to make many containers with the same ingredients and steps. > let's say you have a project that consists of a web application written in Node.js, a backend server written in Java, and a machine learning component written in Python. You can create three separate Docker images for each of these components, each with its own dependencies and configurations, and then use them to create containers that can run the entire project.

For instance, you can create a Docker image for the Node.js application by specifying the base image as node and then copying the application code into the container. You can then build and tag the image with a specific name, like my-node-app.

  • Volumes are like external drives that you can connect to your containers. They let you save data that your containers make or use, such as databases, logs, or configuration files. Volumes do not get deleted when you delete a container. You can also share volumes among many containers or access them from the computer. Volumes are the best way to save data with Docker because they are easier to back up, move, and manage than other ways of saving data. ### โšก Docker Version To check if docker is installed or not, you can run this command in your terminal: 
docker --version
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or

docker version
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or

docker -v
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Let's start with Docker ๐Ÿ”ฅ

If you want to learn the actual thing, you should work on real-world problems that challenge you and make you think. As you try to fix the issues and errors that arise, you will learn more concepts and skills along the way. Thatโ€™s why Iโ€™ll focus on showing you how to work on a real-world application with docker, and how to troubleshoot any problems that may occur. You will also learn how to read documentation, understand complexity, and solve any problem that comes your way. Letโ€™s dive right in!

โœ… Let's play with Postgresql ๐Ÿ˜

โšก Pulling an image

  1. First open this website for postgresql: https://hub.docker.com/_/postgres you will see this right side of the page: 
docker pull postgres
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  1. Open your terminal and type this command: 
docker pull postgres
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  • You can check docker is installed or not by typing this command: docker --version
  • You can visit the docker documentation for pull command: https://docs.docker.com/engine/reference/commandline/pull/
  • Pulling an image doesn't mean installing it. It just means that you are downloading the image from the Docker Hub to your computer.
  • It will download the latest version of the image. If you want to download a specific version, you can add the version number after the image name. For example, docker pull postgres:9.6.2 will download the 9.6.2 version of the image. ### โšก Check the images
  • Now may be you want to check your images, so type this command: 
docker image ls
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You can see the output like this:

REPOSITORY   TAG       IMAGE ID       CREATED        SIZE
postgres     latest    ceccf204404e   30 hours ago   379MB
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Even you can open the docker desktop and check the images there ,and you will see the same output.

โšก Run a container

  1. Now if you want to run postgresql, first you should visit postgresql documentation: https://hub.docker.com/_/postgres check for How to use this image
  2. You will see this: 
$ docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d postgres
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  1. Now open your terminal you need to modify this command: 
docker run -e POSTGRES_PASSWORD=mysecretpassword postgres
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here e is for environment variable, and POSTGRES_PASSWORD is the environment variable name, and mysecretpassword is the value of the environment variable.
now you can
here e is for environment variable, and POSTGRES_PASSWORD is the environment variable name, and mysecretpassword is the value of the environment variable.
now you can see the output like this:

PostgreSQL init process complete; ready for start up.

2023-04-13 13:00:11.415 UTC [1] LOG:  starting PostgreSQL 15.2 (Debian 15.2-1.pgdg110+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
2023-04-13 13:00:11.431 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
2023-04-13 13:00:11.432 UTC [1] LOG:  listening on IPv6 address "::", port 5432
2023-04-13 13:00:11.443 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2023-04-13 13:00:11.455 UTC [62] LOG:  database system was shut down at 2023-04-13 13:00:11 UTC
2023-04-13 13:00:11.465 UTC [1] LOG:  database system is ready to accept connections
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  • If you want to shut down you can simply type wsl --shutdown in your terminal.
  • If you donโ€™t interact with the container, it will eventually exit. However, you can keep the container running by interacting with it or by running it in detached mode using the -d flag when starting the container. For example, docker run -d -e POSTGRES_PASSWORD=mysecretpassword postgres will start the container in detached mode.
  1. Now hit docker run -e POSTGRES_PASSWORD=mysecretpassword -d postgres > One Id will be generated
  2. Now if you want to check your containers on the software, you can see the another container is running with another name.

โšก check the containers

  1. Now if you want to check your containers on the terminal, you can type this command: 
docker ps
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you will see the output like this:

CONTAINER ID   IMAGE      COMMAND                  CREATED         STATUS         PORTS      NAMES
8fee7f681552   postgres   "docker-entrypoint.sโ€ฆ"   2 minutes ago   Up 2 minutes   5432/tcp   beautiful_curie
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โšก Stop and start a container

  1. Now if you want to stop the container, you can type this command: 
docker stop my_container
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  • in my case, my_container is beautiful_curie
  • you can also mention your container id instead of the name.
  • or you can go to the docker desktop and click on the stop button.
  • Now again if you want to run the container, you can type this command: 
docker start my_container
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  • in my case, my_container is beautiful_curie
  • you can do the same thing with the docker desktop.

โšก Pull according to the version

I want to spin up two machines one with postgres latest one with postgres 13.8 rest of the stuff will be same

  1. First hit this command: 
docker run --name postgres-lates -e POSTGRES_PASSWORD=mysecretpassword -d postgres
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Here postgres-lates is the name of the container

  1. Now hit this command: 
docker run --name postgres-old -e POSTGRES_PASSWORD=mysecretpassword -d postgres:13.8
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you will see the output like this:

Unable to find image 'postgres:13.8' locally
13.8: Pulling from library/postgres
e9995326b091: Pull complete
a0cb03f17886: Pull complete
bb26f7e78134: Pull complete
c8e073b7ae91: Pull complete
99b5b1679915: Pull complete
55c520fc03c5: Pull complete
d0ac84d6672c: Pull complete
4effb95d5849: Pull complete
97fd2548fc1e: Pull complete
43e7f13e3769: Pull complete
2898936d5b2e: Pull complete
b4b731b0864d: Pull complete
fbd79522dd4c: Pull complete
Digest: sha256:2b31dc28ab2a687bb191e66e69c2534c9c74107ddb3192ff22a04de386425905
Status: Downloaded newer image for postgres:13.8
309ecc4e9fd6173f9c6173a2b3a07f8cb656e1cefed0b2b92418bbcc10df7379
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First it will check whether the image is present in your local machine or not, if not it will download the image from the docker hub.

  1. Now if you check in your docker desktop, you will see two containers are running.

image

  1. Now you might notice the port number is not showing in the docker desktop so you can check the port number by typing this command: 
docker port postgres-lates
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or,

docker ps
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image

Here you will notice the port number same for both the containers like 5432/tcp this means the port number is 5432. Port number is where the postgres is running if the same port number is running in your local machine then you canโ€™t run the postgres in your local machine.

  • For that you should learn about docker container you can check my blog on docker container here

โšก Stop the container

  1. Here I want to learn about docker container stop so you can check this docker container stop here So I will stop the container by typing this command: 
docker container stop postgres-lates
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  • you can also give the container id instead of the name.
  • no if you hit the command docker container ls you will see the container is stopped.
  • you can also use docker container ls -a to see all the containers. image

โšก Removing all containers

  1. Now if you want to remove all containers you can type this command:
  2. Before removing the container you should check how I find this on internet or stackoverflow check this here 
docker container prune
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you will see the output like this:

WARNING! This will remove all stopped containers.
Are you sure you want to continue? [y/N] y
Deleted Containers:
309ecc4e9fd6173f9c6173a2b3a07f8cb656e1cefed0b2b92418bbcc10df7379
e5dbcda75300b6cebb4c40aad10cfdb4245ce5ac526efef42b02da7e78ea6ed9
8fee7f68155231c08da8a1441be7c196c8fae68f4cb72fb8d35e53669683d44c
04d5b89229259396524f85a0fb222c2f24bc9207e4912240277667fac4a067c6

Total reclaimed space: 63B
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This is dangerous command so be careful while using this command.

โšก Check volumes

  1. Now if you want to check the volumes you can type this command: 
docker volume ls
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image

โœ… Let's play with the mongo ๐Ÿฒ

  1. First pull the mongo image from the docker hub 
docker pull mongo
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  1. Now create a container 
docker run --name my-mongo-one -d mongo
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  1. Now check the container 
docker container ls
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image

โšก Port Mapping

  1. One version of the mongo is running now I want to run another version of the mongo so I will map the port number. 
docker run --name my-mongo-one -p 4000:27017 -d mongo
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then

docker run --name my-mongo-two -p 4001:27017 -d mongo
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image

โšก Docker Logs

  1. Now if you want to see the logs of the container you can type this command:

Logs is basically to see what is happening inside the container and all the details of the container.

docker logs my-mongo-one
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  • You can id instead of the name.

โšก Delete the container

  1. Let's delete the container 
docker container rm my-mongo-one
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โœ… Let's Connect the mongo express with the mongo ??

Our idea is to create a container of the mongo and another container of the mongo express now we will connect the mongo express with the mongo container because mongo express depends on the mongo container.

  • You can assume this Idea for any kind of project.
  • Also in this case you have to give a same network name to both the containers.
  1. First open the documentation of mongo here and mongo express here and check the environment variables and ports and also check docker's documentation on network

โšก Syntax Understanding

  1. If you want to create mongo with network port environment variables you can type this command: 
docker run -p 27017:27017 -e MONGO_INITDB_ROOT_USERNAME=admin -e MONGO_INITDB_ROOT_PASSWORD=password --name mongodb --net mongo-network -d mongo
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  • docker means you are using docker.
  • run means you are running the container.
  • -p means you are mapping the port number in this case you are mapping the port number 27017 to 27017.
  • -e means you are giving the environment variables if you open mongo documentation you will see the environment variables.
  • --name means you are giving the name to the container.
  • --net means you are giving the network name to the container in this case you are giving the network name mongo-network.
  • -d means you are running the container in the background d means detached.
  • mongo means you are pulling the mongo image from the docker hub. ### โšก Better Syntax But you can write this even better way: 
docker run -d \
-p 27017:27017 \
-e MONGO_INITDB_ROOT_USERNAME=admin \
-e MONGO_INITDB_ROOT_PASSWORD=password \
--name mongodb \
--net mongo-network \
mongo
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if you see any network not found error you can create the network by typing this command:

docker network create mongo-network

โšก Lost network finding

  1. Assume you have created the network and you have created the container but you have lost the network name so you can find the network name by typing this command: 
docker network ls
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image

  1. Now we are going to create the mongo express container: 
docker run -d \
-p 8081:8081 \
-e ME_CONFIG_MONGODB_ADMINUSERNAME=admin \
-e ME_CONFIG_MONGODB_ADMINPASSWORD=password \
-e ME_CONFIG_MONGODB_SERVER=mongodb \
--name mongo-express \
--net mongo-network \
mongo-express
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  1. Now check the container 
docker container ls
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  1. Now you can run mongo express on the browser by typing this url: 
http://localhost:8081
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image

Let's Understand the Docker Compose ๐Ÿณ

Docker Compose is a tool that helps you manage multiple containers as a single application. You define your applicationโ€™s services in a YAML file and then use a single command to start or stop all the services. This makes it easy to share and collaborate on projects with others

  1. Create a file named docker-compose.yml and install plugins indent-rainbow and docker-compose
  2. Please use tab instead of space in this file because yml file is similar to python it strictly follows the indentation.
  3. Create two folder Codes and DockerCompose
  4. Inside the DockerCompose folder create a file named docker-compose.yml > - you can name the file anything but it is a good practice to name it docker-compose.yml > - You can use indent-rainbow plugin to make the indentation better.

Inside the docker-compose.yml file type this code:

Step 1

โšก Writing on YML file 

version: '3'
services:
  mongodb:
  mongo-express:
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  • Whatever you wrote on the terminal you have to write it here.

Step 2

Your compose file doesn't know which container to run first, so it could run Express first or it could run mongodb first. We also know that Express relies on mongodb, so it could run mongodb first or maybe it could run Express first. But we know that Express relies on mongodb, so the mongodb containers should be up and running first and then Express should come into the picture. Now there is an option where we can write this container first, then second Express, which is dependent on mongodb. Or we can keep this Express container up and say 'hey, you keep on restarting until you find a connection with mongodb.' The majority of the time people will be using something like 'depends on' for that. So for that, we have to write depends on then we have to write the name of the container, which is mongodb."

version: '3'
services:
  mongodb:
    image: mongo
    container_name: mongodb
    ports:
      - 27017:27017
    environment:
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=password
  mongo-express:
    image: mongo-express
    restart: always
    container_name: mongo-express
    ports:
      - 8081:8081
    environment:
      - ME_CONFIG_MONGODB_ADMINUSERNAME=admin
      - ME_CONFIG_MONGODB_ADMINPASSWORD=password
      - ME_CONFIG_MONGODB_SERVER=mongodb
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  • version means you are using docker-compose version 3.
  • services means you are creating the services.
  • mongodb means you are creating the mongodb service.
  • image means you are pulling the image from the docker hub.
  • container_name means you are giving the name to the container.
  • ports means you are mapping the port number in this case you are mapping the port number 27017 to 27017.
  • environment means you are giving the environment variables if you open mongo documentation you will see the environment variables.
  • restart means you are saying that if the container is stopped then restart it.
  • depends_on means you are saying that this container depends on the mongodb container.
    • ME_CONFIG_MONGODB_SERVER means you are giving the name of the mongodb container.
    • ME_CONFIG_MONGODB_ADMINUSERNAME means you are giving the username of the mongodb container.
    • ME_CONFIG_MONGODB_ADMINPASSWORD means you are giving the password of the mongodb container.
    • ME_CONFIG_MONGODB_SERVER means you are giving the name of the mongodb container.

โšก Running the docker-compose file

  • Now in the terminal type this command: 
docker-compose -f docker-compose.yml up
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This will create the container and run the container. But make sure you are in the same directory where the docker-compose.yml file is located.

  • docker-compose means you are using docker-compose.
  • -f means you are giving the file name.
  • docker-compose.yml means you are giving the file name.
  • up means you are running the container.

image

image

image

image

Now you can see the response in the terminal.

image

  • Now stop the container from docker desktop.
  • And again run the container from the terminal. 
docker-compose -f docker-compose.yml up
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You might see Subham database again when you visit the localhost:8081.
image

Step 3 (Data Persistence)

One of the biggest problems in the Docker world is that data doesnโ€™t persist. This means that the container is a removable or detachable item and anything mentioned in the docker-compose file will be removed when you remove the container. This can actually be a good thing when you are making a sensitive application, especially something like a code engine. There is a chance that someone might throw up malicious code that could corrupt your entire system. But with a Docker container, you donโ€™t have to worry too much because everything just goes away after that. However, in this case, we want to keep this data and understand what is keeping it. For this, we need to understand Docker volumes. Docker Desktop sometimes, in fact most of the time, creates automatic volumes for you, especially for databases. It assumes that you might want to keep this database there. This is where something interesting comes into the picture.

Why do we need to know about data persistence?

  • If you are using a database, you need to know how to persist the data meaning how to keep the data even after you remove the container or even after you restart the container.
  • So here comes the concept of volumes.Volumes are one way to achieve data persistence in a containerized environment. They allow you to store data outside of the containerโ€™s file system so that it can be accessed even if the container is removed or restarted.

โšก Creating a volume in docker-compose file 

version: '3'
services:
  mongodb:
    image: mongo
    container_name: mongodb
    ports:
      - 27017:27017
    environment:
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=password
    volumes:
      - mongodb_data:/data/db
  mongo-express:
    image: mongo-express
    restart: always
    container_name: mongo-express
    ports:
      - 8081:8081
    environment:
      - ME_CONFIG_MONGODB_ADMINUSERNAME=admin
      - ME_CONFIG_MONGODB_ADMINPASSWORD=password
      - ME_CONFIG_MONGODB_SERVER=mongodb
volumes:
  mongodb_data:
    driver: local
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  • Now again do the same thing as we did in the previous step.
    • Stop the container from docker desktop.
    • Run the container from the terminal.
    • Visit the localhost:8081.
    • Create a database.
    • Stop the container from docker desktop.
    • Run the container from the terminal.
    • Visit the localhost:8081.
    • Now you can see the database. image I understand that it is a little bit confusing but don't worry I will explain it in detail.

Let's do some fun stuff so that you can understand it better.

  • step 1: Stop the container by pressing ctrl+c in the terminal.
  • step 2: Now go to your docker-compose.yml file and rename the volume name from mongodb_data to mongodb_data1 like this: 
version: '3'
services:
  mongodb:
    image: mongo
    container_name: mongodb
    ports:
      - 27017:27017
    environment:
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=password
    volumes:
      - mongodb_data1:/data/db
  mongo-express:
    image: mongo-express
    restart: always
    container_name: mongo-express
    ports:
      - 8081:8081
    environment:
      - ME_CONFIG_MONGODB_ADMINUSERNAME=admin
      - ME_CONFIG_MONGODB_ADMINPASSWORD=password
      - ME_CONFIG_MONGODB_SERVER=mongodb
volumes:
    mongodb_data1:
        driver: local
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image

  • step 4: Now create a database name SubhamSecond and create a collection name SubhamSecondCollection and add some data. Start the container again by running the container from the terminal. 
docker-compose -f docker-compose.yml up
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Now if you visit the localhost:8081 you will see the database.
image

  • step 5: Now stop the container from docker desktop or by pressing ctrl+c in the terminal.
  • step 6: Now again change the docker-compose.yml file like this and rename the volume name from mongodb_data1 to mongodb_data means previous volume name. 
version: '3'
services:
  mongodb:
    image: mongo
    container_name: mongodb
    ports:
      - 27017:27017
    environment:
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=password
    volumes:
      - mongodb_data:/data/db
  mongo-express:
    image: mongo-express
    restart: always
    container_name: mongo-express
    ports:
      - 8081:8081
    environment:
      - ME_CONFIG_MONGODB_ADMINUSERNAME=admin
      - ME_CONFIG_MONGODB_ADMINPASSWORD=password
      - ME_CONFIG_MONGODB_SERVER=mongodb
volumes:
    mongodb_data:
        driver: local
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Now again start the container from the terminal.

docker-compose -f docker-compose.yml up
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Now if you visit the localhost:8081 you will see the database CodeXam
image

So this is called data persistence. Now you can understand why we need to know about data persistence.
You can create as many volumes as you want. If you want to know more about data persistence in docker then you can check out this link.

โšก Stop running all containers

ctrl+c doesn't actually stop the container. It just stops the container from running in the terminal. So if you want to stop the container from running then you can use the following command.

docker-compose -f docker-compose.yml down
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AWS also provides you like docker hub. You can store your docker images in AWS ECR (Elastic Container Registry). You can check out this link to know more about AWS ECR.

Our First Project with Docker ๐Ÿš€

Now we are going to create our first project.

  • Step 1: Create a folder name first project and inside that create a file name index.py and requirements.txt
  • Step 2: Now create a file name Dockerfile and paste the following code in it. ### โšก Python Flask App 
FROM python:3-alpine3.15
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
EXPOSE 5000
CMD python ./index.py
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  • FROM python:3-alpine3.15: Specifies the base image to use for the build. In this case, it's python:3-alpine3.15, which is a lightweight Python 3 image based on Alpine Linux.
  • WORKDIR /app: Sets the working directory for the build to /app. All subsequent commands will be run from this directory.
  • COPY . /app: Copies the contents of the current directory (i.e., the directory containing the Dockerfile) into the /app directory in the image.
  • RUN pip install -r requirements.txt: Runs the command pip install -r requirements.txt to install the dependencies specified in requirements.txt.
  • EXPOSE 5000: Informs Docker that the container will listen on port 5000 at runtime.
  • CMD python ./index.py: Sets the default command to run when the container starts to python ./index.py.
  • Step 3: Open the index.py file and paste the following code in it. 
from flask import Flask
helloworld = Flask(__name__)

@helloworld.route("/")
def run():
    return "{ \"message\": \"Hey there I am Subham\" }"

if __name__ == "__main__":
    helloworld.run(host="0.0.0.0", port=int("5000"), debug=True)
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  • This is a simple flask app. It will return a json object when you visit the localhost:5000.
  • Don't worry if you don't understand the code. If you really want to learn flask , then you can think of it as of now assume that it is a simple flask app that returns a json object or hello world type of thing.
  • Step 4: Open the requirements.txt file and paste the following code in it. 
Flask==2.2.3
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  • Step 5: Now open the terminal and go to the first project folder and run the following command. ### โšก Build the docker image 
docker build -t subham4041/first-flask-app:0.0.1.RELEASE .
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  • docker build -t: This command is used to build the docker image.
  • subham4041/first-flask-app: This is the name of the docker image. here subham4041 is my docker hub username and first-flask-app is the name of the docker image.
  • 0.0.1.RELEASE: This is the version of the docker image you can change it to whatever you want.
  • .: This is the path of the dockerfile. In this case, it is the current directory.

You can see the docker image in the docker desktop.

image

โšก Run the docker image

  • Step 6: Now run the following command to check if the docker image is working or not. 
docker run -d -p 5000:5000 subham4041/first-flask-app:0.0.1.RELEASE
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You will see the something like this 9ff963bcb47695be360e0974224604dcd46782b8606.........
you can check using docker ps command.

  • Step 7: Now visit the localhost:5000 and you will see the following output. 
{
  "message": "Hey there I am Subham"
}
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image

โšก Stop the docker container

  • Step 8: Now stop the docker container using the following command. 
docker container stop 684dfe64fad50af65280f603f5...........
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or

docker container stop 9ff
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  • No need to write the full container id. You can write the first 3-4 characters of the container id.
  • docker container stop: This command is used to stop the docker container and you can see the container id in the terminal.

โšก Mapping the port

  • Step 9: While it is not possible to change the main port of a Docker container, you can map a port on your local machine to the containerโ€™s port. 
docker run -d -p 8000:5000 subham4041/first-flask-app:0.0.1.RELEASE
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  • docker run -d -p 8000:5000: This command is used to map the port 8000 of the local machine to the port 5000 of the docker container.
  • subham4041/first-flask-app:0.0.1.RELEASE: This is the name of the docker image.
  • Now visit the localhost:8000 and you will see the following output. 
{
  "message": "Hey there I am Subham"
}
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  • Step 10: Now stop the docker container using the following command. 
docker container stop 684
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  • No need to write the full container id. You can write the first 3-4 characters of the container id.
  • Step 11: Let's push the docker image to the docker hub.

โšก Push the docker image to the docker hub 

docker push subham4041/first-flask-app:0.0.1.RELEASE
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image

Our Second Project with Docker ๐Ÿš€

Our second project is a simple nodejs app that returns a json object.

โšก Nodejs Setup

Install nodejs in your system you can download it from here.

If you don't have any idea about nodejs don't worry this is a simple demo app so there is no need to understand the code in detail. We will completely focus on how docker works. If you know nodejs then you can easily understand the code also.

  • Step 1: Create a new folder and name it second project.
  • Step 2: Open the terminal and go to the second project folder and run the following command. 
npm init -y
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Basically, this command will create a package.json file where all the dependencies will be stored.

  • Step 3: Now just replace the script inside the package.json file with the following code. 
"scripts": {
    "start": "node index.js"
  },
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image

Let me explain what does it mean.

  • scripts: This is the key in the package.json file.
  • start: This is the name of the script.
  • node index.js: This is the command that will run when we run the npm start command.
  • So basically, when we run the npm start command it will run the node index.js command.
  • node is a javascript runtime environment. It is used to run javascript code outside the browser.
  • index.js: This is the name of the file where we will write our code and using the node environment we will run the code.
  • Step 4: Now just install the express module using the following command. 
npm install express
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  • npm install express: This command is used to install the express module.
  • npm is a package manager for the javascript runtime environment node.
  • express: This is a nodejs framework. It is used to create a web application.
  • You can see the node_modules folder in the second project folder.
  • Step 5: Now create a new file and name it index.js and paste the following code in it. 
const express = require('express');
const app = express();
const port = 5000;

app.get('/', (req, res) => {
  res.json({ message: 'Hello World!' });
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});
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No need to worry about the code. This is similar to the flask app we created in the first project. We are just returning a json object.

  • Step 6: Now run the following command to start the app. 
npm start
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hit this in the terminal and you will see the following output.

Example app listening at http://localhost:5000
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Now visit the localhost:5000 and you will see the following output.

{
  "message": "Hello World!"
}
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image

โšก Login to the docker hub

First, you need to login to the docker hub using the following command.

docker login
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You will see the following output.

Logging in with your password grants your terminal complete access to your account.
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  • Step 7: Now stop the app using the ctrl+c command then delete the node_modules folder and create a new file and name it Dockerfile and paste the following code in it. 
FROM node:14.17.0-alpine3.13
WORKDIR /app
COPY . /app
RUN npm install
EXPOSE 5000
CMD node index.js
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  • Step 8: Now run the following command to build the docker image. 
docker build -t subham4041/second-node-app:0.0.1.RELEASE .
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  • docker build -t subham4041/second-node-app:0.0.1.RELEASE .: This command is used to build the docker image.
  • docker build: This is the command to build the docker image.
  • -t subham4041/second-node-app:0.0.1.RELEASE: This is the name of the docker image.
    • subham4041: This is the docker hub username. You will get this when you log in to the docker hub.
    • second-node-app: This is the name of the docker image.
    • 0.0.1.RELEASE: This is the version of the docker image.
  • .: This is the path of the dockerfile. In our case, it is the current directory.

now you will see something like this.
image

  • Step 9: Now check how many docker images running in your system using the following command. 
docker ls
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You will see the following output.

CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES
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  • CONTAINER ID: This is the id of the container.
  • IMAGE: This is the name of the docker image.
  • COMMAND: This is the command that is running inside the container.
  • CREATED: This is the time when the container was created.
  • STATUS: This is the status of the container.
  • PORTS: This is the port number of the container.
  • NAMES: This is the name of the container.
  • You can see that there is no docker image running in your system.
  • Step 10: Now run the following command to run the docker image. 
docker run -d -p 5001:5000 subham4041/second-node-app:0.0.1.RELEASE
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  • docker run -d -p 5001:5000 subham4041/second-node-app:0.0.1.RELEASE: This command is used to run the docker image.
  • docker run: This is the command to run the docker image.
  • -d: This is used to run the docker image in the background.
  • -p 5001:5000: This is used to map the port number of the docker image to the port number of the host machine.
  • subham4041/second-node-app:0.0.1.RELEASE: This is the name of the docker image.
  • You can see that the docker image is running in the background.
  • Step 11: Now check how many docker images running in your system using the following command. 
docker ps
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You will see the following output.

CONTAINER ID   IMAGE                                     COMMAND                  CREATED          STATUS          PORTS                    NAMES
b3b0b5b5b9b0   subham4041/second-node-app:0.0.1.RELEASE   "docker-entrypoint.sโ€ฆ"   10 seconds ago   Up 9 seconds
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  • Step 12: Now visit the localhost:5001 and you will see the following output. 
{
  "message": "Hello World!"
}
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  • Step 13: Now run the following command to push the docker image to the docker hub. 
docker push subham4041/second-node-app:0.0.1.RELEASE
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image

  • Step 14: Now let's delete the docker image from the local system using the following command.

You can do this using the docker desktop app also.

โšก Check the container id

First, you need to check the image id using the following command.

docker ps
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โšก Stop the container

Now run the following command to stop the container.

docker stop <container_id>
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In my case, the container id is b3b0b5b5b9b0 so I will run the following command docker stop b3b0b5b5b9b0.

โšก Kill the container

Now run the following command to kill the container.

docker kill <container_id>
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This will send a signal to the container to gracefully stop. If you want to forcefully stop the container immediately, you can use the docker kill command instead:docker stop <container_id>

โšก Remove the container

You can remove the container using the docker rm command followed by the container ID. For example, to remove the container with ID b9061e6d08b6, you can use the following command:

docker rm b9061e6d08b6
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โšก Remove the image

After removing the container, you can then delete the image using the docker rmi command:

docker rmi <image_id>
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In my case, the image id is a0dacd3ecd79e1252ca8e8a655902af1b6ae98ee609cdee91056c67a6ca00a5c so I will run the following command docker rmi a0dacd3ecd79e1252ca8e8a655902af1b6ae98ee609cdee91056c67a6ca00a5c.
This will delete the image from your system.

  • Step 15: Now run the following command to pull the docker image from the docker hub. ### โšก Pull the docker image 
docker pull subham4041/second-node-app:0.0.1.RELEASE
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  • Step 16: Now run the following command to run the docker image. 
docker run -d -p 5001:5000 subham4041/second-node-app:0.0.1.RELEASE
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Now visit the localhost:5001 and you will see the following output.

{
  "message": "Hello World!"
}
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๐Ÿฅฐ What did we understand from these two projects?

If someone pulls the docker image from the docker hub, then they don't need to install the nodejs and npm in their system. They just need to install the docker in their system and then they can run the docker image and they can easily access the application without installing the nodejs and npm in their system. This is the magic of docker.

โœจ Docker CLI Cheat Sheet

1. Installation

Command Meaning Syntax
For Windows This command helps you to install Docker on Windows. https://download.docker.com/win/stable/InstallDocker.msi
For Linux This command helps you to install Docker on Linux. `curl -sSL https://get.docker.com/
For Mac This command helps you to install Docker on Mac OS. {% raw %}https://download.docker.com/mac/stable/Docker.dmg

2. Docker Registry and Repository

Command Meaning Syntax
Login to a Registry This command helps you log in to your Registry. docker login [options] [server]
Logout from a registry This command helps you log out from your Registry. docker logout [server]
Searching an image By using this docker command you can search any image from your docker. docker search [options] term
Pulling an image This command can be used to download a specific image or set of images. docker pull [options] name[:tag]
Pushing an image This command can be used to push a specific image or set of images. docker push [options] name[:tag]

3. Running Containers

Command Meaning Syntax
Running a container from an image This command creates and starts a container from an image. You can specify various options such as ports, volumes, environment variables, etc. docker run [options] image[:tag] [command] [args]
Listing running containers This command shows all the containers that are currently running. You can use filters and format options to customize the output. docker ps [options]
Listing all containers (running and stopped) This command shows all the containers that exist on your system, regardless of their status. You can use filters and format options to customize the output. docker ps -a [options]
Stopping a container This command stops a running container by sending a SIGTERM signal and then a SIGKILL signal if the container does not stop within a grace period. You can specify multiple containers to stop at once. docker stop [options] container [container...]
Starting a stopped container This command starts a stopped container by restoring its state. You can specify multiple containers to start at once. docker start [options] container [container...]
Restarting a container This command restarts a running or stopped container by stopping and then starting it again. You can specify multiple containers to restart at once. docker restart [options] container [container...]
Removing a container This command removes one or more containers from your system. You can use filters and force options to remove containers that are running or have volumes attached to them. docker rm [options] container [container...]

4. Managing Images

Command Meaning Syntax
Building an image from a Dockerfile This command builds an image from a Dockerfile and optionally tags it with a name and tag. You can specify various options such as build arguments, cache settings, etc. docker build [options] path
Removing an image from your system This command removes one or more images from your system. You can use filters and force options to remove images that are in use or have dependent images. docker rmi [options] image [image...]
Tagging an image with a name and tag This command assigns a name and tag to an image. You can use this to create aliases for images or to prepare them for pushing to a registry. docker tag [options] image[:tag] name[:tag]
Saving an image to a tar archive This command saves one or more images to a tar archive file. You can use this to backup or transfer images between systems. docker save [options] image [image...] -o file
Loading an image from a tar archive This command loads one or more images from a tar archive file. You can use this to restore or import images from a backup or another system. docker load [options] -i file

5. Managing Volumes

Command Meaning Syntax
Creating a volume This command creates a volume on your system. You can specify various options such as name, driver, labels, etc. docker volume create [options] [name]
Listing volumes on your system This command shows all the volumes that are stored on your system. You can use filters and format options to customize the output. docker volume ls [options]
Inspecting a volume This command shows detailed information about a specific volume. You can use this to check the status, driver, mount point, etc. of a volume. docker volume inspect [options] volume [volume...]
Removing a volume from your system This command removes one or more volumes from your system. You can use filters and force options to remove volumes that are in use or have dependent containers. docker volume rm [options] volume [volume...]
Pruning unused volumes from your system This command removes all the volumes that are not referenced by any containers from your system. You can use filters to exclude some volumes from pruning. docker volume prune [options]

6. Managing Networks

Command Meaning Syntax
Creating a network This command creates a network on your system. You can specify various options such as name, driver, subnet, etc. docker network create [options] [name]
Listing networks on your system This command shows all the networks that are available on your system. You can use filters and format options to customize the output. docker network ls [options]
Inspecting a network This command shows detailed information about a specific network. You can use this to check the status, driver, IP range, connected containers, etc. of a network. docker network inspect [options] network [network...]
Removing a network from your system This command removes one or more networks from your system. You can use filters and force options to remove networks that are in use or have dependent containers. docker network rm [options] network [network...]
Pruning unused networks from your system This command removes all the networks that are not used by any containers from your system. You can use filters to exclude some networks from pruning. docker network prune [options]

7. Miscellaneous Commands (continued)

Command Meaning Syntax
Getting help on docker commands and options This command shows the usage and options for any docker command or subcommand. You can use this to learn more about how to use docker. docker [command] --help
Getting the version of docker This command shows the version and build information of docker on your system. You can use this to check if you have the latest version or if you need to update. docker version [options]
Getting system-wide information on docker This command shows system-wide information about docker on your system. You can use this to check the status, resources, configuration, etc. of docker. docker info [options]
Executing a command in a running container This command executes a command in a running container and returns the output. You can use this to run commands that are not available in the container's shell or to interact with the container's processes. docker exec [options] container command [args]
Attaching to a running container This command attaches your terminal to a running container's standard input, output, and error streams. You can use this to interact with the container's shell or processes. docker attach [options] container
Copying files or folders between a container and your system This command copies files or folders between a container and your system. You can use this to transfer data to or from a container. docker cp [options] source destination
Viewing logs from a container This command shows the logs from a container's standard output and error streams. You can use this to monitor or troubleshoot a container's activity. docker logs [options] container
Committing changes to an image This command creates a new image from a container's changes. You can use this to save your modifications or to create new images based on existing ones. docker commit [options] container [repository[:tag]]
Building an image from stdin or a URL This command builds an image from a Dockerfile that is provided through stdin or a URL. You can use this to build images from remote sources or scripts. docker build [options] - < Dockerfile or docker build [options] url
Showing the history of an image This command shows the history of an image, including the layers and commands that were used to create it. You can use this to inspect how an image was built or to optimize it. docker history [options] image

๐Ÿ“Œ Conclusion

Congratulations! You have completed this tutorial on Docker and learned how to use it for various purposes. You have also created some amazing projects using Docker that showcase your skills and creativity. You should be proud of yourself!

Now you can experiment with whatever you want with Docker and explore its endless possibilities. You can also improve this tutorial with a pull request or add more content if you have any suggestions or ideas. Your feedback is always welcome and appreciated.

Thank you for reading this tutorial and following along. I hope you enjoyed it and learned something new. Happy Docking! ๐Ÿ˜Š

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