By Tony Tran
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, you’ll demonstrate how to install Docker Compose on a Rocky Linux 9 server and how to get started using this tool.
To follow this article, you will need:
To make sure you obtain the most updated stable version of Docker Compose, you’ll download this software from the official Docker repository.
First, let’s update the package database:
- sudo dnf check-update
Next, add the official Docker repository if you didn’t do so during your Docker install:
- sudo dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
While there is no Rocky Linux specific repository from Docker, Rocky Linux is based upon CentOS and can use the same repository. Now you can install Docker Compose, which is a plugin for Docker:
- sudo dnf install docker-compose-plugin
To verify that the installation was successful, you can run:
- docker compose version
You’ll see output similar to this:
OutputDocker Compose version v2.10.2
Docker Compose is now successfully installed on your system. In the next section, you’ll see how to set up a
docker-compose.yml file and get a containerized environment up and running with this tool.
To demonstrate how to set up a
docker-compose.yml file and work with Docker Compose, you’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:
- mkdir app
Using your preferred text editor, create a new
index.html file within the
- nano app/index.html
Place the following content into this file:
<!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
ENTER to confirm.
Next, create the
- nano docker-compose.yml
Insert the following content in your
version: '3.7' services: web: image: nginx:alpine ports: - "8000:80" volumes: - ./app:/usr/share/nginx/html
docker-compose.yml file typically starts off with the
version definition. This will tell Docker Compose which configuration version you’re using.
You then have the
services block, where you set up the services that are part of this environment. In your case, you 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.
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.
You 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, you’ll bring this environment up with Docker Compose.
docker-compose.yml file in place, you can now execute Docker Compose to bring your 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 up -d
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:
OutputCreating 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
Note: If you run into a permission error regarding the Docker socket, this means you skipped Step 2 of How To Install and Use Docker on Rocky Linux 9. Going back and completing that step will enable permissions to run docker commands without
Your environment is now up and running in the background. To verify that the container is active, you can run:
- docker compose ps
This command will show you information about the running containers and their state, as well as any port redirections currently in place:
OutputName 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.
You’ll see a page like this:
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.
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
- docker compose logs
You’ll see output similar to this:
OutputAttaching 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:
- docker compose pause
OutputPausing compose-demo_web_1 ... done
To resume execution after issuing a pause:
- docker compose unpause
OutputUnpausing compose-demo_web_1 ... done
stop command will terminate the container execution, but it won’t destroy any data associated with your containers:
- docker compose stop
OutputStopping compose-demo_web_1 ... done
If you want to remove the containers, networks, and volumes associated with this containerized environment, use the
- docker compose down
OutputRemoving 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 your 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
OutputUntagged: 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.
In this guide, you’ve seen how to install Docker Compose and set up a containerized environment based on an Nginx web server image. You’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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