Docker Basics

Preface:

Docker is an open source application container engine that allows developers to package their applications and dependencies into a portable image and then publish it to any popular Linux or Windows machine. In recent years, Docker has been developing rapidly in China, especially in Internet companies. The use of Docker is very common, which has greatly improved the maintenance efficiency of applications and reduced the cost of cloud computing application development. This article mainly introduces you to Docker and its installation and simple use.

1. Install Docker

To learn Docker, we must first install Docker. Since version 17.03, it is divided into CE (Community Edition) and EE (Enterprise Edition). Below we take the CentOS system as an example to introduce the installation of Docker Community Edition:

Uninstall old versions

The old version of Docker is called docker or docker-engine. Use the following command to uninstall the old version:

$ sudo yum remove docker \
         docker-client \
         docker-client-latest \
         docker-common \
         docker-latest \
         docker-latest-logrotate \
         docker-logrotate \
         docker-engine

Install dependency packages

#Configure yum source sudo yum-config-manager \
--add-repo \
https://mirrors.ustc.edu.cn/docker-ce/linux/centos/docker-ce.repo

#Install dependent packages sudo yum install -y yum-utils \
device-mapper-persistent-data \
lvm2

Install the latest version of Docker CE

sudo yum-config-manager --enable docker-ce-edge
sudo yum makecache fast
sudo yum install docker-ce

Start Docker CE

sudo systemctl enable docker
sudo systemctl start docker

Create a docker user group

sudo groupadd docker
sudo usermod -aG docker $USER

Run the hello-world test

$ docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
ca4f61b1923c: Pull complete
Digest: sha256:be0cd392e45be79ffeffa6b05338b98ebb16c87b255f48e297ec7f98e123905c
Status: Downloaded newer image for hello-world:latest
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon creates a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
https://hub.docker.com/

For more examples and ideas, visit:
https://docs.docker.com/get-started/

So far, we have successfully installed Docker. Similarly, it is also very easy to install Docker on Windows and macOS. You can download the Docker Desktop installation package to install and use it. For details, please refer to the following official documents:

https://docs.docker.com/docker-for-windows/install/
https://docs.docker.com/docker-for-mac/install/

2. Introduction to common commands

To learn Docker, we must first understand its overall architecture. Here is a brief introduction to three basic concepts in Docker:

• Image: A Docker image is equivalent to a root file system. For example, the official image ubuntu:16.04 contains a complete root file system of the Ubuntu 16.04 minimal system.
• Container: The relationship between an image and a container is like that between a class and an instance in object-oriented programming. An image is a static definition, and a container is an entity at the image runtime. Containers can be created, started, stopped, deleted, paused, etc.
• Repository: A repository is a code control center used to store images.
  

Mirror related commands:

1) Searching for images
docker search image name (such as redis)

2) Download the image
docker pull image name

3) View the local mirror list
docker images

4) Delete the image
docker rmi image ID

Container related commands:

1) Run the image as a container
docker run --name container name -d image name
-d stands for detached, which means that after executing this command, the console will not be blocked and you can continue to enter commands.
2) Get a list of running containers
docker ps
3) Get a list of all containers containing exit comments
docker ps -a
4) Stop and start the container
docker start/stop container name/id

5) Port mapping requires mapping the port of the software running in the container to the port of the host, otherwise the host in the LAN will not be able to access it.
docker run -d -p 6378:6379 --name myRedis redis
-p: Map port 6379 in the container to port 6378 on the host
6) Delete the container
docker rm id
7) View the current container log
docker logs name/id
8) Log in to the container
docker exec -it container name bash
-i: Ensure that our input is valid
-t: A pseudo terminal will be allocated to log in to the current container. After logging in, you can perform regular Linux command operations in the container, and you can also use the exit command to log out.

Summarize:

This article briefly introduces the installation and common commands of Docker. As an introductory article, I hope it will be helpful to you. In fact, as Docker is a basic tool, it is recommended that you learn it. For example, you can start a MySQL instance in seconds, and you can also use Docker to run and test new versions. The next article will describe how to run and configure MySQL in Docker, so stay tuned!

The above is the detailed content of the simple introductory tutorial on Docker. For more information on getting started and using Docker, please pay attention to other related articles on 123WORDPRESS.COM!