How to Use Docker CLI on AlmaLinux

Containers have revolutionized the way developers build, test, and deploy applications. Among container technologies, Docker remains a popular choice for its simplicity, flexibility, and powerful features. AlmaLinux, a community-driven distribution forked from CentOS, offers a stable environment for running Docker. If you’re new to Docker CLI (Command-Line Interface) or AlmaLinux, this guide will walk you through the process of using Docker CLI effectively.

Understanding Docker and AlmaLinux

Before diving into Docker CLI, let’s briefly understand its importance and why AlmaLinux is a great choice for hosting Docker containers.

What is Docker?

Docker is a platform that allows developers to build, ship, and run applications in isolated environments called containers. Containers are lightweight, portable, and ensure consistency across development and production environments.

Why AlmaLinux?

AlmaLinux is a robust and open-source Linux distribution designed to provide enterprise-grade performance. As a successor to CentOS, it’s compatible with Red Hat Enterprise Linux (RHEL), making it a reliable choice for deploying containerized applications.

Prerequisites for Using Docker CLI on AlmaLinux

Before you start using Docker CLI, ensure the following:

1. AlmaLinux installed on your system.
2. Docker installed and configured.
3. A basic understanding of Linux terminal commands.

Installing Docker on AlmaLinux

If Docker isn’t already installed, follow these steps to set it up:

1. Update the System:

   sudo dnf update -y
   

2. Add Docker Repository:

   sudo dnf config-manager --add-repo=https://download.docker.com/linux/centos/docker-ce.repo
   

3. Install Docker Engine:

   sudo dnf install docker-ce docker-ce-cli containerd.io -y
   

4. Start and Enable Docker Service:

   sudo systemctl start docker
   sudo systemctl enable docker
   

5. Verify Installation:

   docker --version
   

Once Docker is installed, you’re ready to use the Docker CLI.

Getting Started with Docker CLI

Docker CLI is the primary interface for interacting with Docker. It allows you to manage containers, images, networks, and volumes directly from the terminal.

Basic Docker CLI Commands

Here’s an overview of some essential Docker commands:

• docker run: Create and run a container.
• docker ps: List running containers.
• docker images: List available images.
• docker stop: Stop a running container.
• docker rm: Remove a container.
• docker rmi: Remove an image.

Let’s explore these commands with examples.

1. Running Your First Docker Container

To start a container, use the docker run command:

docker run hello-world

This command downloads the hello-world image (if not already available) and runs a container. It’s a great way to verify your Docker installation.

Explanation:

• docker run: Executes the container.
• hello-world: Specifies the image to run.

2. Listing Containers

To view running containers, use the docker ps command:

docker ps

Options:

• -a: Show all containers (including stopped ones).
• -q: Display only container IDs.

Example:

docker ps -a

This will display a detailed list of all containers.

3. Managing Images

Images are the building blocks of containers. You can manage them using Docker CLI commands:

Pulling an Image

Download an image from Docker Hub:

docker pull ubuntu

Listing Images

View all downloaded images:

docker images

Removing an Image

Delete an unused image:

docker rmi ubuntu

4. Managing Containers

Docker CLI makes container management straightforward.

Stopping a Container

To stop a running container, use its container ID or name:

docker stop <container-id>

Removing a Container

Delete a stopped container:

docker rm <container-id>

5. Creating Persistent Storage with Volumes

Volumes are used to store data persistently across container restarts.

Creating a Volume

docker volume create my_volume

Using a Volume

Mount a volume when running a container:

docker run -v my_volume:/data ubuntu

6. Networking with Docker CLI

Docker provides powerful networking options for container communication.

Listing Networks

docker network ls

Creating a Network

docker network create my_network

Connecting a Container to a Network

docker network connect my_network <container-id>

7. Docker Compose: Enhancing CLI Efficiency

For complex applications requiring multiple containers, use Docker Compose. It simplifies the management of multi-container environments using a YAML configuration file.

Installing Docker Compose

sudo dnf install docker-compose

Running a Compose File

Navigate to the directory containing docker-compose.yml and run:

docker-compose up

8. Best Practices for Using Docker CLI on AlmaLinux

1. Use Descriptive Names:
   Name your containers and volumes for better identification:

   docker run --name my_container ubuntu
   

2. Leverage Aliases:
   Simplify frequently used commands by creating shell aliases:

   alias dps='docker ps -a'
   

3. Clean Up Unused Resources:
   Remove dangling images and stopped containers to free up space:

   docker system prune
   

4. Enable Non-Root Access:
   Add your user to the Docker group for rootless access:

   sudo usermod -aG docker $USER
   

   Log out and log back in for the changes to take effect.

5. Regular Updates:
   Keep Docker and AlmaLinux updated to access the latest features and security patches.

Conclusion

Using Docker CLI on AlmaLinux unlocks a world of opportunities for developers and system administrators. By mastering the commands and best practices outlined in this guide, you can efficiently manage containers, images, networks, and volumes. AlmaLinux’s stability and Docker’s flexibility make a formidable combination for deploying scalable and reliable applications.

Start experimenting with Docker CLI today and see how it transforms your workflow. Whether you’re running simple containers or orchestrating complex systems, the power of Docker CLI will be your trusted ally.