1. What is Docker ?:
Docker is a software platform that allows you to build, test, and deploy applications quickly. Docker packages software into standardized units called containers that have everything the software needs to run including libraries, system tools, code, and runtime. Using Docker, you can quickly deploy and scale applications into any environment and know your code will run.
2. How Docker work ?:
Docker works by providing a standard way to run your code. Docker is an operating system for containers. Similar to how a virtual machine virtualizes (removes the need to directly manage) server hardware, containers virtualize the operating system of a server. Docker is installed on each server and provides simple commands you can use to build, start, or stop containers.
3. Docker image:
A Docker image is a read-only template that contains a set of instructions for creating a container that can run on the Docker platform. It provides a convenient way to package up applications and preconfigured server environments, which you can use for your own private use or share publicly with other Docker users.
4. Docker container:
A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another. A Docker container image is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries, and settings.
5. Docker volume:
Volumes are the preferred mechanism for persisting data generated by and used by Docker containers. While bind mounts are dependent on the directory structure and OS of the host machine, volumes are completely managed by Docker. Volumes have several advantages over bind mounts:
- Volumes are easier to back up or migrate than bind mounts.
- You can manage volumes using Docker CLI commands or the Docker API.
- Volumes work on both Linux and Windows containers.
- Volumes can be more safely shared among multiple containers.
- Volume drivers let you store volumes on remote hosts or cloud providers, to encrypt the contents of volumes, or add other functionality.
- New volumes can have their content pre-populated by a container.
- Volumes on Docker Desktop have much higher performance than bind mounts from Mac and Windows hosts
6. Docker network:
One of the reasons Docker containers and services are so powerful is that you can connect them together, or connect them to non-Docker workloads. Docker containers and services do not even need to be aware that they are deployed on Docker, or whether their peers are also Docker workloads or not. Whether your Docker hosts run Linux, Windows, or a mix of the two, you can use Docker to manage them in a platform-agnostic way.
7. Docker Hub:
Share and Collaborate with Docker Hub. Docker Hub is the world’s largest repository of container images with an array of content sources including container community developers, open-source projects, and independent software vendors (ISV) building and distributing their code in containers. Users get access to free public repositories for storing and sharing images or can choose a subscription plan for private repos.
8. How to use Docker with docker-compose and Docker Hub:
- What about docker-compose:
Docker Compose is a tool that was developed to help define and share multi-container applications. With Compose, we can create a YAML file to define the services and with a single command, can spin everything up or tear it all down.
The big advantage of using Compose is you can define your application stack in a file, keep it at the root of your project repo (it’s now version controlled), and easily enable someone else to contribute to your project. Someone would only need to clone your repo and start the compose app. In fact, you might see quite a few projects on GitHub/GitLab doing exactly this now.
- How to install PostgreSQL with Docker Hub and docker compose:
- Download Office Postgres Image from Docker Hub with the command:
- docker pull postgres
- Attention: We can use docker run with a lot of parameters to run this database, but this way is very confusing, so I recommend using docker-compose instead.
- Create docker-compose.yml:
# Use postgres/example user/password credentials version: '3.1' services: db: image: postgres restart: always environment: POSTGRES_PASSWORD: postgres POSTGRES_USER: postgres POSTGRES_DB: postgres ports: - 5436:5432 adminer: image: adminer restart: always ports: - 8080:8080
- Open terminal, change directory to folder that contain this docker-compose.yml file, then type below command: docker-compose up -d
- Open localhost:8080 to open adminer with password=postgres and fill the value for other input like this image:
9. Why Use Docker:
Using Docker lets you ship code faster, standardize application operations, seamlessly move code, and save money by improving resource utilization. With Docker, you get a single object that can reliably run anywhere. Docker's simple and straightforward syntax gives you full control. Wide adoption means there's a robust ecosystem of tools and off-the-shelf applications that are ready to use with Docker.