An article to understand the creation, uploading, pulling and deployment of Docker images

1. Images

1. What is a mirror?

(1) According to Baidu Encyclopedia: Mirroring is a form of file storage and a type of redundancy. The data on one disk has an identical copy on another disk, which is called a mirror.

(2) You can make many files into a mirror file, put it on a disk with programs such as GHOST, and then open it with software such as GHOST, and then restore it into many files. RAID 1 and RAID 10 use mirroring.

(3) Common image file formats include ISO, BIN, IMG, TAO, DAO, CIF, and FCD.

Do you feel more dizzy after watching it?

In fact, to put it simply, an image is a package of an app, which contains program code, basic system, dependency libraries, and tools.
To put it more simply, it is a bit like an APP installation package.

2. Composition and purpose of images

(1) Dockerfile

： is the recipe for making the image file

Like a secret recipe passed down from generation to generation: Yunnan Baiyao: Linzhi, ginseng, deer antler, Panax notoginseng, etc.

(2) Scratch

： It is the most basic Docker image, which is equivalent to a foundation - > blank image, nothing - > starting from scratch

Use other images as base images: Other images can be extended based on it - just like standing on the shoulders of giants.

But we need to build a mirror step by step.

(3) A complete operating system requires:

1.kernel
2. System calls
3. Applications and Libraries
4. Shell, etc.

bootfs --》Contents required when the container is started

rootfs --》Operating system inside the container

docker save

docker export

principle:

When the container starts, the kernel starts bootfs and directly loads the base image, and then loads it layer by layer – from bottom to top

When accessing files after the container is running, access is done from top to bottom, from the writable layer, layer by layer.

3. Why should you make your own image?

In the past, to download MySQL in Linux and CentOS systems, you had to use the yum command. After learning the docker technology, you can get any software you need by just pulling it on docker. Docker is like a huge resource library. It only has things you can't think of.

Some students said: It was technology that limited my imagination of docker, and they shed tears of regret.

Some students said, since Docker is so convenient and has so many image files, why do we need to make them ourselves? Can't we just pull whatever we need?

However, companies often need to make their own image files because they are often unsure about what others make, or some specific needs cannot be met. Just like when you go to buy Moutai, and the merchant says it is ten-year-old Moutai, would you believe him? Is this the Moutai of the past ten years? Why don't you go and get it identified? If you are a rich person, just pretend I didn't say anything, hahaha

2. Steps of mirror making (10-step method)

Step 1: Edit Dockerfile

[root@sc-docker-server ~]# mkdir /mydocker/
[root@sc-docker-server ~]# cd /mydocker/
[root@sc-docker-server mydocker]#

[root@sc-docker-server mydocker]# vim Dockerfile
FROM python:2.7-slim
WORKDIR /app
ADD ./app
RUN pip install --trusted-host pypi.python.org -r requirements.txt
EXPOSE 80
ENV NAME World
ENV AUTHOR cali
CMD ["python","app.py"]

Step 2: Edit requirements.txt file

[root@sc-docker-server mydocker]# vim requirements.txt
Flask
Redis

Step 3: Edit the app.py file, our program file

[root@sc-docker-server mydocker]# vim app.py
from flask import Flask
from redis import Redis, RedisError
import os
import socket

# Connect to Redis
redis = Redis(host="redis", db=0, socket_connect_timeout=2, socket_timeout=2)

app = Flask(__name__)

@app.route("/")
def hello():
    try:
        visits = redis.incr("counter")
    except RedisError:
        visits = "<i>cannot connect to Redis, counter disabled</i>"

    html = "<h3>Hello {name}!</h3>" \
           "<b>Hostname:</b> {hostname}<br/>" \
           "<b>Visits:</b> {visits}"
    return html.format(name=os.getenv("NAME", "world"), hostname=socket.gethostname(), visits=visits)

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80)

Step 4: Generate image file

[root@sc-docker-server mydocker]#docker build -t sc_friendlyhello_1 .
docker build -t sc_friendlyhello_1 .
Sending build context to Docker daemon 4.608kB
Step 1/9: FROM python:2.7-slim
 ---> eeb27ee6b893
Step 2/9: WORKDIR /app
 ---> Using cache
 ---> 81aa71984f63
Step 3/9: ADD ./app
 ---> Using cache
 ---> a5c7c6ed471c
Step 4/9: VOLUME ["/data_flask"]
 ---> Using cache
 ---> d4db66a741db
Step 5/9 : RUN pip install --trusted-host pypi.python.org -r requirements.txt
 ---> Using cache
 ---> bcdee009e5f7
Step 6/9: EXPOSE 80
 ---> Using cache
 ---> 475474ce55ff
Step 7/9: ENV NAME World
 ---> Using cache
 ---> 0f03ead6c99b
Step 8/9: ENV AUTHOR cali
 ---> Using cache
 ---> f844eb0f1a78
Step 9/9 : CMD ["python","app.py"]
 ---> Using cache
 ---> ab30484b56b8
Successfully built ab30484b56b8
Successfully tagged sc_friendlyhello_1:latest
[root@sc-docker-server mydocker]#

Step 5: Check if the image is successful

[root@sc-docker-server mydocker]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
sc_friendlyhello_1 latest ab30484b56b8 32 minutes ago 159MB

Step 6: Use the image to start the container

docker run -d -p 5080:80 --name sc-hello-1 sc_friendlyhello_1

Step 7: Access the container's web service

Use curl or Chrome browser to access the host ip:5080

Hello World!
Hostname: f4aeb5d5305a
Visits: cannot connect to Redis, counter disabled

Because the redis database container is not started, the flask web service cannot connect to the redis database

Step 8: Start the redis container

docker run -d -p 6379：6379 --name sc-redis-1 redis

Step 9: Start a container with your own image again and link it to the redis container

docker run -d --name sc-hello-2 -p 5081:80 --link sc-redis-1:redis sc_friendlyhello_1

Step 10: Access the container's web service

Use curl or chrome browser to access the host ip:5081

Hello World!
Hostname: aad7da1892b5
Visits: 15

3. Mirror image creation

Operation

1. Upgrade the base image in the image of sc_friendlyhello_1 to python:3.9
Rename your own image to sc_friendlyhello_2
2. Start the container and redis container and test access**

Operation steps:

Install uploaded files

root@sc-docker-server ~]# yum install lrzsz -y Install the uploaded software. Last metadata expiration check: 0:25:32 ago, executed on Wednesday, August 18, 2021 at 09:52:02.
Package lrzsz-0.12.20-43.el8.x86_64 is already installed.
Dependency resolution.
No treatment is required.
complete!
[root@sc-docker-server ~]#

Step 1: Download the app source code

https://github.com/docker/getting-started Download in Windows, then upload to Linux yum install git -y 

In Linux: git clone https://github.com/califeng/getting-started.git

Step 2: Unzip the app source code archive

[root@sc-docker-server ~]# yum install zip unzip -y

    [root@sc-docker-1 ~]# unzip getting-started-master.zip 

Step 3: Enter the app directory and create a new Dockerfile

    [root@sc-docker-1 getting-started-master]# cd app/
    [root@sc-docker-1 app]# vim Dockerfile
FROM node:12-alpine
WORKDIR /app
COPY . .
RUN yarn install --production
CMD ["node", "src/index.js"]

Step 4: Make the mirror

[root@sc-docker-1 app]# docker build -t getting-started .
-t getting-started is the name of the specified image. You can define your own name [root@sc-docker-1 app]# docker images View the created image REPOSITORY TAG IMAGE ID CREATED SIZE
getting-started latest 5b903e857b8c 25 seconds ago 179MB
redis latest cc69ae189a1a 2 days ago 105MB
nginx 1.19.7 35c43ace9216 7 days ago 133MB
nginx latest 35c43ace9216 7 days ago 133MB
mysql 5.7.33 5f47254ca581 2 weeks ago 449MB
nginx 1.19.6 f6d0b4767a6c 6 weeks ago 133MB
node 12-alpine 0206ff8a5f9e 7 weeks ago 88.9MB
richarvey/nginx-php-fpm latest 5c3ad1891297 5 months ago 506MB
hello-world latest bf756fb1ae65 13 months ago 13.3kB
jcdemo/flaskapp latest 4f7a2cc79052 2 years ago 88.7MB
[root@sc-docker-1 app]#

Step 5: Start the container of your own image

[root@sc-docker-1 app]# docker run -dp 3000:3000 getting-started
8f150a72e7d2d1650685b00a18d237469fa07c8cd56977773dd266b281a3b4ad
[root@sc-docker-1 app]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8f150a72e7d2 getting-started "docker-entrypoint.s…" 5 seconds ago Up 3 seconds 0.0.0.0:3000->3000/tcp strange_benz
deabb58e01b0 nginx "/docker-entrypoint.…" 26 hours ago Up 2 hours 0.0.0.0:6655->80/tcp chenpeng
[root@sc-docker-1 app]# 

Step 6: Open the browser to access the website in the container

Website in the container: http://192.168.0.161:3000/

Summarize

1. Image creation is an essential skill in Docker technology. If you say you know Docker, others will definitely ask you if you know how to create images? When you ask them why they make that thing, they will smile knowingly and think that this person’s skills must be very low since he can’t even do this and yet he says he knows Docker. Haha.

2. There are detailed steps for mirror production later. The ten-step method of mirror production will teach you how to do it. Take your time and do it step by step.

This is the end of this article about Docker image creation, uploading, pulling and deployment. For more relevant Docker image creation, uploading, pulling and deployment content, please search for previous articles on 123WORDPRESS.COM or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!