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      How To Install and Use Docker Compose on Ubuntu 20.04


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      Introduction

      Docker simplifies the process of managing application processes in containers. While containers are similar to virtual machines in certain ways, they are more lightweight and resource-friendly. This allows developers to break down an application environment into multiple isolated services.

      For applications depending on several services, orchestrating all the containers to start up, communicate, and shut down together can quickly become unwieldy. Docker Compose is a tool that allows you to run multi-container application environments based on definitions set in a YAML file. It uses service definitions to build fully customizable environments with multiple containers that can share networks and data volumes.

      In this guide, we’ll demonstrate how to install Docker Compose on an Ubuntu 20.04 server and how to get started using this tool.

      Prerequisites

      To follow this article, you will need:

      Step 1 — Installing Docker Compose

      To make sure we obtain the most updated stable version of Docker Compose, we’ll download this software from its official Github repository.

      First, confirm the latest version available in their releases page. At the time of this writing, the most current stable version is 1.26.0.

      The following command will download the 1.26.0 release and save the executable file at /usr/local/bin/docker-compose, which will make this software globally accessible as docker-compose:

      • sudo curl -L "https://github.com/docker/compose/releases/download/1.26.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

      Next, set the correct permissions so that the docker-compose command is executable:

      • sudo chmod +x /usr/local/bin/docker-compose

      To verify that the installation was successful, you can run:

      You’ll see output similar to this:

      Output

      docker-compose version 1.26.0, build 8a1c60f6

      Docker Compose is now successfully installed on your system. In the next section, we’ll see how to set up a docker-compose.yml file and get a containerized environment up and running with this tool.

      Step 2 — Setting Up a docker-compose.yml File

      To demonstrate how to set up a docker-compose.yml file and work with Docker Compose, we’ll create a web server environment using the official Nginx image from Docker Hub, the public Docker registry. This containerized environment will serve a single static HTML file.

      Start off by creating a new directory in your home folder, and then moving into it:

      • mkdir ~/compose-demo
      • cd ~/compose-demo

      In this directory, set up an application folder to serve as the document root for your Nginx environment:

      Using your preferred text editor, create a new index.html file within the app folder:

      Place the following content into this file:

      ~/compose-demo/app/index.html

      <!doctype html>
      <html lang="en">
      <head>
          <meta charset="utf-8">
          <title>Docker Compose Demo</title>
          <link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/kognise/water.css@latest/dist/dark.min.css">
      </head>
      <body>
      
          <h1>This is a Docker Compose Demo Page.</h1>
          <p>This content is being served by an Nginx container.</p>
      
      </body>
      </html>
      

      Save and close the file when you’re done. If you are using nano, you can do that by typing CTRL+X, then Y and ENTER to confirm.

      Next, create the docker-compose.yml file:

      Insert the following content on your docker-compose.yml file:

      docker-compose.yml

      version: '2.0'
      services:
        web:
          image: nginx:alpine
          ports:
            - "8000:80"
          volumes:
            - ./app:/usr/share/nginx/html
      

      The docker-compose.yml file typically starts off with the version definition. This will tell Docker Compose which configuration version we’re using.

      We then have the services block, where we set up the services that are part of this environment. In our case, we have a single service called web. This service uses the nginx:alpine image and sets up a port redirection with the ports directive. All requests on port 8000 of the host machine (the system from where you’re running Docker Compose) will be redirected to the web container on port 80, where Nginx will be running.

      The volumes directive will create a shared volume between the host machine and the container. This will share the local app folder with the container, and the volume will be located at /usr/share/nginx/html inside the container, which will then overwrite the default document root for Nginx.

      Save and close the file.

      We have set up a demo page and a docker-compose.yml file to create a containerized web server environment that will serve it. In the next step, we’ll bring this environment up with Docker Compose.

      Step 3 — Running Docker Compose

      With the docker-compose.yml file in place, we can now execute Docker Compose to bring our environment up. The following command will download the necessary Docker images, create a container for the web service, and run the containerized environment in background mode:

      Docker Compose will first look for the defined image on your local system, and if it can’t locate the image it will download the image from Docker Hub. You’ll see output like this:

      Output

      Creating network "compose-demo_default" with the default driver Pulling web (nginx:alpine)... alpine: Pulling from library/nginx cbdbe7a5bc2a: Pull complete 10c113fb0c77: Pull complete 9ba64393807b: Pull complete c829a9c40ab2: Pull complete 61d685417b2f: Pull complete Digest: sha256:57254039c6313fe8c53f1acbf15657ec9616a813397b74b063e32443427c5502 Status: Downloaded newer image for nginx:alpine Creating compose-demo_web_1 ... done

      Your environment is now up and running in the background. To verify that the container is active, you can run:

      This command will show you information about the running containers and their state, as well as any port redirections currently in place:

      Output

      Name Command State Ports ---------------------------------------------------------------------------------- compose-demo_web_1 /docker-entrypoint.sh ngin ... Up 0.0.0.0:8000->80/tcp

      You can now access the demo application by pointing your browser to either localhost:8000 if you are running this demo on your local machine, or your_server_domain_or_IP:8000 if you are running this demo on a remote server.

      Note: if you are running this demo on a remote server that has the UFW firewall enabled, you’ll have to allow access on port 8000 in order to be able to access the demo from a browser running on your local machine:

      You’ll see a page like this:

      Docker Compose Demo Page

      Because the shared volume you’ve set up within the docker-compose.yml file keeps your app folder files in sync with the container’s document root. If you make any changes to the index.html file, they will be automatically picked up by the container and thus reflected on your browser when you reload the page.

      In the next step, you’ll see how to manage your containerized environment with Docker Compose commands.

      Step 4 — Getting Familiar with Docker Compose Commands

      You’ve seen how to set up a docker-compose.yml file and bring your environment up with docker-compose up. You’ll now see how to use Docker Compose commands to manage and interact with your containerized environment.

      To check the logs produced by your Nginx container, you can use the logs command:

      You’ll see output similar to this:

      Output

      Attaching to compose-demo_web_1 web_1 | /docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration web_1 | /docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/ web_1 | /docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh web_1 | 10-listen-on-ipv6-by-default.sh: Getting the checksum of /etc/nginx/conf.d/default.conf web_1 | 10-listen-on-ipv6-by-default.sh: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf web_1 | /docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh web_1 | /docker-entrypoint.sh: Configuration complete; ready for start up web_1 | 172.22.0.1 - - [02/Jun/2020:10:47:13 +0000] "GET / HTTP/1.1" 200 353 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36" "-"

      If you want to pause the environment execution without changing the current state of your containers, you can use:

      Output

      Pausing compose-demo_web_1 ... done

      To resume execution after issuing a pause:

      Output

      Unpausing compose-demo_web_1 ... done

      The stop command will terminate the container execution, but it won’t destroy any data associated with your containers:

      Output

      Stopping compose-demo_web_1 ... done

      If you want to remove the containers, networks, and volumes associated with this containerized environment, use the down command:

      Output

      Removing compose-demo_web_1 ... done Removing network compose-demo_default

      Notice that this won’t remove the base image used by Docker Compose to spin up your environment (in our case, nginx:alpine). This way, whenever you bring your environment up again with a docker-compose up, the process will be much faster since the image is already on your system.

      In case you want to also remove the base image from your system, you can use:

      • docker image rm nginx:alpine

      Output

      Untagged: nginx:alpine Untagged: nginx@sha256:b89a6ccbda39576ad23fd079978c967cecc6b170db6e7ff8a769bf2259a71912 Deleted: sha256:7d0cdcc60a96a5124763fddf5d534d058ad7d0d8d4c3b8be2aefedf4267d0270 Deleted: sha256:05a0eaca15d731e0029a7604ef54f0dda3b736d4e987e6ac87b91ac7aac03ab1 Deleted: sha256:c6bbc4bdac396583641cb44cd35126b2c195be8fe1ac5e6c577c14752bbe9157 Deleted: sha256:35789b1e1a362b0da8392ca7d5759ef08b9a6b7141cc1521570f984dc7905eb6 Deleted: sha256:a3efaa65ec344c882fe5d543a392a54c4ceacd1efd91662d06964211b1be4c08 Deleted: sha256:3e207b409db364b595ba862cdc12be96dcdad8e36c59a03b7b3b61c946a5741a

      Note: Please refer to our guide on How to Install and Use Docker for a more detailed reference on Docker commands.

      Conclusion

      In this guide, we’ve seen how to install Docker Compose and set up a containerized environment based on an Nginx web server image. We’ve also seen how to manage this environment using Compose commands.

      For a complete reference of all available docker-compose commands, check the official documentation.



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