How to Start or Run Docker Daemon

Docker has had a significant impact on the development, shipping, and deployment of applications. By using containerization, Docker allows a developer to package an application along with all the dependencies into standard units termed containers. This way, it makes sure the application behaves uniformly across any environment, starting from development to production.

The Docker daemon is the core of all the functionalities that Docker gives, which means the component responsible for the heavy lifting in building, running, and managing Docker containers. The Docker daemon receives requests for the Docker API and processes them, enabling users to manage the creation, execution, and management of Docker objects like images, containers, networks, and volumes. The ability to start and control the Docker daemon is probably one of the very first skills that every single Docker developer and system administrator should learn.

In this article, we will discuss the essential steps for starting and running the Docker daemon on multiple operating systems. We define vital terminologies, give a step-by-step guide, and describe some common issues you might experience. By the time you are done with this guide, you should be able to get the Docker daemon up and running, the failure of which you cannot correctly containerize your applications.

Primary Terminologies

• Docker Daemon: A daemon is a Dockerized background service that manages and allows operations for Docker objects, such as images, containers, networks, and volumes, it listens to Docker API requests and processes them to build, run, and manage Docker containers.
• Docker CLI: The Docker CLI, or command-line interface, is a tool for interacting with the Docker daemon. For example, running an image or building a new container is achieved with commands like docker run, docker build, or docker ps to control and manage the Docker environment.
• Container: A lightweight, stand-alone, executable software package that includes everything needed to run an application—code, runtime, system tools, libraries, and settings. They isolate containers from one another and the host system so that they are consistent across all infrastructures.
• Image: A read-only template used in creating containers. In this template, there is application code, runtime, libraries, environment variables, and configuration files. Images are built as layered and incremental changes, one layer at a time from the previous layer. Images can be stored in container registries, for example, Docker Hub.
• Dockerfile: A Dockerfile is a text document that contains the necessary commands for creating an image in Docker. The Dockerfile consists of instructions on a base image, application code, dependencies, configuration settings, and commands to run within the container.
• Docker Hub: Docker Hub is a cloud-based registry service that enables users to store and distribute Docker images, it provides both public and private repositories, allowing sharing of the photos with other users or downloading images managed by Docker and other companies.
• Volume: A volume is available, independent of an individual container, for the life span of the container. On the contrary, volumes are stored on the host file system and, hence, can be shared between many containers. Volumes are pretty handy for persisting data and managing state across container restarts.
• Network: A Docker network is a communication link that permits interchange between two different Docker containers and between containers and host systems. Docker provides various kinds of network drivers for various networking needs: bridge, host, overlay, and so forth.

Step-by-Step Process to Start or Run Docker Daemon

Step 1: Launch EC2 Instance

• Go to AWS Console and login with your credentials
• Navigate to EC2 dashboard and launch ec2 instance

Step 2: Install docker

• Before starting the Docker daemon, ensure Docker is installed on your system. Install docker by using following commands.

sudo yum -y install docker

Step 3: Install dockerNow start docker by using following command

sudo systemctl start docker

• To enable the Docker daemon to start on boot

sudo systemctl enable docker

Verify Docker Daemon Status

• To verify that the Docker daemon is running, use the following command:

sudo systemctl status docker

Troubleshoot Docker Daemon Issues

Common Issues:

• Permission Issues: Ensure your user is added to the Docker group.

sudo usermod -aG docker $USER
newgrp docker

Configuration Issues: Check the Docker configuration file located at /etc/docker/daemon.json.

Port Conflicts: Ensure no other service is using Docker’s default port (2375).

• Ensure there are no port conflicts on the Docker default port (2375)

sudo netstat -tuln | grep 2375

• There is no any port conflicts and docker port was running successfully
• Check the Docker daemon logs for errors:

sudo journalctl -u docker

Examples

Example 1: Running a Simple Container

• Once the Docker daemon is running, you can run a simple container. For instance, to run an Nginx container:

docker run -d -p 80:80 nginx

This command pulls the Nginx image from Docker Hub (if not already present) and runs it in detached mode (-d), mapping port 80 of the host to port 80 of the container.

Example 2: Checking Running Containers

• To list all running containers:

docker ps

• To list all containers (including stopped ones):

docker ps -a

Conclusion

Starting and managing the Docker daemon is a baseline skill for anyone working with Docker, including development, testing, or production environments. The Docker daemon is the backbone of Docker's architecture, creating, managing, and running containers. Wielding the full force of containerization in your applications requires knowledge about installing Docker, starting the daemon, and troubleshooting common issues.

Throughout this manual, we have explored the procedures for enabling Docker Daemon start-up on various platforms: Ubuntu, CentOS, macOS, and Windows. We defined essential terminologies to lay a good foundation for understanding Docker's components and operation. Follow these instructions with illustrative examples to configure and verify the operation of the Docker daemon by yourself. Have a smooth and productive containerization experience.

You will be in a position to master these concepts to enhance workflows, increase the portability of applications, and simplify deployment. Docker enables this: consistency and predictability about application environments from development to production, free us developers' time and attention to make us more effective at what we do.