docker Foundation

Preface

This is an article I wrote after three weeks of spare time study. My understanding of docker is still at the beginning stage. I hope this article can help some friends who want to learn docker get started quickly. The exercises and actual combat codes are in the github repository. If my article can help you, you can give it to me. docker project Give me a compliment.

introduce

Docker is an open source application container engine. Developers can package their own applications in the container and then migrate to docker applications on other machines to achieve rapid deployment. If a failure occurs, the service can be quickly restored by mirroring.

For example, companies generally have multiple environments, so how to keep multiple environments consistent, docker can be used at this time. And when you need to add an environment, you don't need to install and configure one environment after another on a new server. Just run the docker. Officials also provided Docker Hub It has a large number of high-quality official images. You can upload your own image. It's a bit like github.

install

Officials have provided installation tutorials, which are very detailed. Official Installation Course

docker starts

Step 1: The docker is successfully installed under the docker-v confirmation

If installed successfully, the command line will output the version number of docker. As follows:
Docker version 18.09.2, build 6247962

The whole life cycle of docker can be roughly divided into:

1. image
2. container
3. Warehouse

Here, take ubuntu mirror as an example to introduce the lower mirror

Before downloading the ubuntu image, run docker images to view the local image. If you haven't downloaded the mirror yet, of course it will be empty. Here's my local mirror.

➜ study-docker git:(master) ✗ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
todolist_static latest de5e325037e9 2 hours ago 1.05GB
todolist_nodejs latest 53efd80e03e1 2 hours ago 898MB
ubuntu 18.04 7698f282e524 4 weeks ago 69.9MB
mysql latest 990386cbd5c0 5 weeks ago 443MB
node 8 a5c31320f223 6 weeks ago 895MB
mysql 5.6 73829d7b6139 6 weeks ago 256MB

Use the pull mirror command docker pull to pull the Ubuntu image: docker pull ubuntu. When you do not specify a version, the latest version is pulled by default.

➜ study-docker git:(master) ✗ docker pull ubuntu
Using default tag: latest
latest: Pulling from library/ubuntu
5b7339215d1d: Pull complete 
14ca88e9f672: Pull complete 
a31c3b1caad4: Pull complete 
b054a26005b7: Pull complete 
Digest: sha256:9b1702dcfe32c873a770a32cfd306dd7fc1c4fd134adfb783db68defc8894b3c
Status: Downloaded newer image for ubuntu:latest
➜ study-docker git:(master) ✗ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu latest 4c108a37151f 12 hours ago 64.2MB

Specified version mirrors can also be installed: docker pull ubuntu:18.04

Next, start a container based on the ubuntu image

docker run --name first -it ubuntu bash

• --name is used to specify the container name
• It is used for interactive command-line operations. After running the following example, it opens the container's command line
• The Ubuntu above refers to the mirror image, which is based on latest by default. Unless specified version such as ubuntu:18.04

After running the above command, the command line tool automatically enters the container's command line. If you want to exit the command line interface, enter exit to exit.

➜ study-docker git:(master) ✗ docker run --name first -it ubuntu bash
root@b7862a018c2c:/# 

If you want the container to run in the background, you can add-d configuration to make the container run in the background. The command line tool does not enter the container when running in the background.

Use docker ps to view currently running containers.

➜ study-docker git:(master) ✗ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
cf8375f48225 ubuntu "bash" 15 seconds ago Up 14 seconds first

Use - d to let the container run in the background

➜ study-docker git:(master) ✗ docker run --name first -itd ubuntu bash
6df29a09d1f1bb0041b7eb59b5288162471ed8a663007f88c6a30e3fd1f4fbe2

The command line returns the container id

Use docker containers to view a list of all containers (excluding stopped containers)

➜ study-docker git:(master) ✗ docker container ls -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
cf8375f48225 ubuntu "bash" About a minute ago Up About a minute first

Stop the container using docker stop <container id or container name>.

➜ study-docker git:(master) ✗ docker stop 6df29a09d1f1
6df29a09d1f1

When the command is executed, the id of the container you just entered is returned. The container id above does not need to be filled in. Just like git's commit id.

At this time, the container information can not be found through docker container ls. You need to use docker container ls-a to view.

➜ study-docker git:(master) ✗ docker container ls -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6df29a09d1f1 ubuntu "bash" 5 minutes ago Exited (0) 4 minutes ago

You can see in the STATUS column that the container is in a stop state.

Use docker RM < container id or container nickname >

➜ node git:(master) docker container ls -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a217eea7188f ubuntu "/bin/bash" 11 seconds ago Exited (0) 10 seconds ago dreamy_ishizaka

Execute docker rm a21 (id can not be lost)

➜ node git:(master) docker rm a21
a21

After execution, the command line returns the container id entered before.

Use docker container prune to empty the container in the deactivated state.

Use the docker exec command to enter the running container

If you want to enter the interactive interface of the container just running in the background: docker exec-it < container name or container ID > Bash

➜ study-docker git:(master) ✗ docker exec -it first bash
root@2a87b2f62a6e:/#

Want to see more about docker commands, click here

Dockerfile

An example of node mirroring

Create a new folder

I'll create a new folder called node, which can refer to my github project. node directory

// index.js
const express = require('express');
const app = express();
app.get('/', (req, res) => {
    res.end('success')
})
app.listen(6001)

// Dockerfile
FROM node:8
WORKDIR /home/node
COPY ../ ../
RUN npm install
CMD npm start

Introduction to Directives

• FROM My node example is based on node8 mirroring
• WORKDIR specifies the workspace.
• COPY Copies Local Directory Files into docker
• RUN runs a container, and each RUN generates a container
• CMD executes commands, similar to RUN

Note that it's necessary to add a. dockerignore file, which can fill in files that you don't want to pack into containers. Similar to. gitignore

// .dockerignore
/node_modules
package-lock.json

Detailed explanation, see dockerfile

➜ node git:(master) ✗ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
mynode latest 3cd10521f802 10 hours ago 898MB

Next, run a node container based on the image:

docker run --name mynode -p 4001:6001 mynode

• --name: denotes the container's anonymity
• - p: Represents port mapping, because the host's IP is different from the container's ip, it is necessary to map the container's services to 0.0.0:the host port set by itself. The host does not fill in the defau lt of 0.0.0.0. Host Port >: <Port in Container >;

➜ node git:(master) ✗ docker run --name mynode -p 4001:6001 mynode
> example2@1.0.0 start /home/node
> node index.js

The browser accesses localhost:4001, and the page shows the success string of the node response.

After building the image, you don't think you need the image. What if you want to delete it?

First execute: docker images list mirrors

➜ node git:(master) ✗ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
mynode latest 3cd10521f802 10 hours ago 898MB

Use docker RMI < image ID > to delete the image: docker rmi 3cd10521f802. If you remind the image to be occupied by the container, you need to delete the container first (refer to the command described above).