Steadylearner

Posted on May 16, 2021 • Edited on Jun 23, 2023 • Originally published at steadylearner.com

How to use Docker commands

#docker #tutorial #beginners #devops

In this post, we'll learn how to use Docker commands. We will make a web app inside a Docker container and turn it into a Docker image. We'll also learn how to upload it to Docker Hub.

You can find Portuguese version of this post here.

Prerequisite

First, you must install Docker, if you don't have it yet. Type $docker on your machine and you will be shown how to proceed with the installation. Or just search how to install it on your browser.

This post is a summary of Docker Website, Docker Curriculum etc. I hope you read them first, but you don't have to spend a lot of time with them. We'll learn how to deploy a web app and microservices to AWS with other Steadylearner Blog posts.

Confirm installation with Nginx
Set up your development environment with Docker
How to move your local files and folders to docker containers
How to use the web framework with docker containers
How to modify the network ports of docker images
Docker Images and Containers
How to upload your Docker images to Docker Hub
Conclusion

1. Confirm installation with Nginx

I hope you can install Docker. Before we learn how each Docker command works, let's test whether or not these can show some results on your machine.

Use them in your CLI.

$docker search nginx
$docker pull nginx
$docker run --name nginx-webserver -p 80:80 nginx

Then, access localhost. This will be shown in your browser:

Welcome to nginx!

If you see this page, the nginx web server is successfully installed and working. Further configuration is required.

For online documentation and support please refer to nginx.org.
Commercial support is available at nginx.com.

Thank you for using nginx.

Realize that you only need a few commands to use Docker. You could also start a Docker container with a specific name and execute bash comamnds with these.

$docker run --name nginx-webserver -p 80:80 -d nginx
$docker exec -it CONTAINER_ID bash

2. Set up your development environment with Docker

In this section, we'll learn how to set up a default Docker image with Ubuntu. It will be possible to reuse this image later. If you use another OS, please, use that instead and refer to this part.

Start with pull commands to download the official ubuntu image from Docker Hub. If Docker Hub is something new for you, you can compare it to GitHub because of its repositories.

$docker pull ubuntu

Now, make a container in your machine. To download minimal softwares, use sh or bash commands in it with this:

$docker run -it ubuntu sh

Start by installing CURL to download other programs.

$apt-get update
$apt-get install curl
$curl https://www.steadylearner.com

If you are out of the container, restart it with this:

$docker exec -it CONTAINER_ID bash

You can find the CONTAINER_ID with docker ps -a. This is the command you will use often and it will show you some useful metadata of Docker containers.

We'll make a simple Node "Hello, World" web app example in this post. Let's start by configuring the Node development environment. Follow these steps if you want to use the same project as this post.

Also, you can use $docker run -d steadylearner/ubuntu_node instead.

You should be inside your docker container to use them.

Node, NPM, Yarn

curl -sL https://deb.nodesource.com/setup_12.x | bash

This will be displayed:

## Run `sudo apt-get install -y nodejs` to install Node.js 12.x and npm
## You may also need development tools to build native addons:
    sudo apt-get install gcc g++ make
## To install the Yarn package manager, run:
    curl -sL https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
    echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
    sudo apt-get update &amp;&amp; sudo apt-get install yarn

You should use commands without sudo.

apt-get install gcc g++ make
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list

apt-get update &amp;&amp; apt-get install yarn

Follow those commmands and install them all.

Test Node work with this:

$node
$console.log("Hello from www.steadylearner.com");

Vim

Use this command with --assume-yes or -y to skip relevant install questions.

apt install --assume-yes vim

Vim text editor will be installed. Now, use this command to use it:

$vim hello.js

Edit your hello.js file with this and :wq to save and quit from the Vim.

// hello.js
console.log("Hello from www.steadylearner.com");

Use this command to verify that Node is installed correctly:

$node hello.js
// Hello from www.steadylearner.com

Git

$apt-get --assume-yes git-core

This will install Git and verify that it is installed and its version:

$git --version

Then, get your GitHub username and email from your local machine:

$git config --get user.name
$git config --get user.email

Use them in the Docker container to operate Git inside:

$git config --global user.name yourname
$git config --global user.name youremail

Make use of the same command (--get) before checking them in your Docker container.

Test Git clone work to download files from your previous GitHub repositories. For example, clone steadylearner/docker-examples repository with this:

$git clone https://github.com/steadylearner/docker-examples.git

I hope you can install everything you think is necessary in your Docker container.

You can skip this Yarn relevant part and use default npm commands instead. Otherwise, read this post for more information.

Verify the Yarn version first in it.

$yarn -v

It will show the version of your Yarn.

Next, use these commands to use Node project:

$cd /home
$mkdir node && cd node
$yarn init
$yarn add chalk

Test NPM or Yarn work with NPM modules with these:

// Start with $node in your console and use each command.

const chalk = require("chalk");
const blue = chalk.blue;
const hello = blue("Hello from www.steadylearner.com");
console.log(hello);

It should have shown Hello from www.steadylearner.com message in your console.

We verified that NPM packages work in your docker container with this.

If you want, make alias for this directory also similar to this.

$vim ~/.bashrc

Type this and :wq to save and quit.

alias work="cd /home/node"

Use $source ~/.bashrc and you can use your node project with $work whenever you want. Also, you can define WORKDIR later with Dockerfile or docker-compsose.yml for the same purpose.

There will be many Docker containers in your machine. Use these commands to remove unnecessary ones:

1. List and remove previous Docker containers.

$docker ps -a

The list of instances that you ran before will be shown.

2. Remove what you don't need.

$docker stop containerid
$docker rm containerid

$docker rm containerid -f

3. How to move your local files and folders to docker containers

We can use Git commands to download files from the GitHub into your containers. Moreover, you can use Docker commands to move local files and folders to your Docker containers and vice versa.

Refer to these examples or docker cp --help.

1. Files

$docker cp from_localhost.txt containerid:/from_localhost.txt
$docker cp containerid:/from_docker from_docker.txt

2. Folders

$docker cp from_localhost containerid:/from_localhost
$docker cp containerid:/from_localhost from_localhost

4. How to use web frameworks with docker containers

We installed Node relevant softwares for this part. If you use web frameworks from other languages, please, refer only to the workflow of this section.

Express

Install the dependencies we'll use inside the docker container with this:

$yarn add express chalk

Next, we'll build "Hello, World!" app with the JavaScript code below.

// server.js
const express = require('express')
const chalk = require("chalk");

const app = express()
const port = 3000

app.get('/', (req, res) =&gt; res.send('Hello, World!'))

const blue = chalk.blue
const target = blue(`http://localhost:${port}`)

app.listen(port, () =&gt; console.log(`Express Server ready at ${target}`))

Then, $node server.js will display this message:

[Express] Server ready at http://localhost:3000

But $curl http://localhost:3000 or visiting it in your browser won't work yet.

Each container has its own IP to network. We should inspect the docker container with $docker inspect CONTAINER_ID > inspect.txt to extract the information from it.

You can find its local IP at the end of inspect.txt and it will be similar to 172.17.0.2. Save your time doing getIP.js and $node getIP.js.

const fs = require('fs')

const filename = "inspect.txt";

fs.readFile(filename, 'utf8', function(err, data) {
  if (err) throw err;

  // console.log(`Read ${filename}`);
  const dataObject = JSON.parse(data);

  // console.log(payload);
  // console.log(typeof payload);

  const ip = dataObject[0].NetworkSettings.IPAddress;
  console.log(`IP is ${ip}`);
});

You can use the docker inspect command as well.

Test the IP with $curl http://172.17.0.2:3000/ or verify it with your browser.

If you can see this message, realize that you can actually develop web apps on your local machine with Docker.

Hello, World!

5. How to modify the network ports of docker images

In the previous part, we had to find the network port for the web framework to visit it. Alternatively, you can start with your custom port.

$docker run -it --name ubuntu_node -p 80:80 ubuntu

You can also use it with -d to make the container run in background..

docker run -d --name ubuntu_node -p 80:80 ubuntu:latest

Refer to this to find out what happens here better.

'By default, the port on the host (container) is mapped to 0.0.0.0, which means all IP addresses. You can specify a particular IP when defining the port mapping, for example, -p 127.0.0.1:80:80'

6. Docker Images and Containers

You may find yourself confused by the difference between Docker container and image. Just think of the images as classes and containers as instances that you are using on your machine. You can:

Pull or run (pull and start) images and it will make docker containers from them on your local machine.
Edit files in your containers with $docker exec -it containername bash.
Make images from the containers with $docker commit containername YourDockerHub/image && docker push account/image.

Feel free to start with Dockerfile instead of 1. and 2. and commit your docker images as well. We'll learn that in another Steadylearner Blog with Elastic Beanstalk.

7. How to upload your Docker images to Docker Hub

Now, we are going to learn how to create a repository first at Docker Hub with the example we made.

First, login with this command:

$docker login

Then, use $docker commit.

$docker commit ubuntu_node

Next, verify the image made from the ubuntu_node container using this:

$docker images

Give it a tag (name).

$docker tag imageid steadylearner/ubuntu_node

You can execute this command instead:

$docker commit ubuntu_node steadylearner/ubuntu_node

Now, you can push your docker image to Docker Hub with this:

$docker push steadylearner/ubuntu_node // yourusername/image

Wait for uploading process to complete and use this:

$docker run -it steadylearner/ubuntu_node bash

If you want to edit it, just follow the same steps we used before.

Restart the containers with this, if they stop:

$docker restart containerid
$docker exec -it containerid bash

To remove container made from steadylearner/ubuntu_node image or yours, you can use this:

$docker stop ubuntu_node
$docker container rm ubuntu_node
$docker image rm ubuntu

If you want to rename the container, use this:

$docker container rename randomname ubuntu_node

Use yours instead of ubuntu_node or steadylearner/ubuntu_node.

If you modify the project, use the commands similar to this:

$docker commit ubuntu_node steadylearner/ubuntu_node

Or with a commit message.

$docker commit --message "Test message and will be similar to github -m option" ubuntu_node steadylearner/ubuntu_node

Now, let's push the image made from it to Docker Hub:

$docker push steadylearner/ubuntu_node

and use this:

$docker run -it steadylearner/ubuntu_node bash

or this, to verify the result:

$docker history steadylearner/ubuntu_node

8. Conclusion

I hope you made it all work. We learned how to install Docker and make it work with Nginx, how to make a Docker container and image and upload them into Docker Hub.

There are many things to learn. But everything will be easier with examples. In the later posts on the Steadylearner Blog, we will learn how to deploy the web app with Elastic Beanstalk from AWS and Dockerfile. We will also learn how to deploy micro services with ECS, CloudFormation, docker-compose.yml etc. So, keep an eye out for updates!

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Reviewed by Mariana Santos

Refer to these commands if you want more. Use the ID or the name of the containers for them.

Logs of the container

$docker logs containerid | name

History of the image

#docker history steadylearner/ubuntu_node

Remove unused images

$docker images
$docker image rm dockerimagename or docker rmi

Rename the container

$docker rename randomname whatyouwant

Pause and unpause the containers

$docker pause containerid | name
$docker ps -a
$docker unpuase containerid | name
$docker ps -a

Start and stop them

$docker stop containerid | name
$docker ps -a
$docker start containerid | name
$docker ps -a

Remove containers

$docker container rm containerid | name

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