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Use of Docker mirrors

The first two chapters introduce the basics of containers. In this chapter, we introduce the simple use of images. Image hub contains various images contributed from all over the world, including images of beginners and learning practitioners. Today, we use one of the official images for learning exercises (https://github.com/docker-training/webapp)).

Download the startup container

# bring down the image pull first

Docker pull training/webapp

# View the current image list

Docker images

# you can see the webapp we just downloaded

REPOSITORY TAG IMAGE ID CREATED SIZE

Training/webapp latest 6fae60ef3446 4 years ago 349MB

# run webapp instance

#-d is running in the background

#-P means that the instance network is mapped to the local machine, because this webapp will listen on the tcp port. In addition, the listening tcp port in the parameter container and the local tcp port, so that we can directly access the corresponding port on the local machine to establish a connection with the port that the container instance listens to.

Docker run-d-P training/webapp python app.py

# View the running instance

Docker ps-a

# return information

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

5da522ffe229 training/webapp "python app.py" 2 minutes ago Up 2 minutes 0.0.0.0 minutes ago Up 1024-> 5000/tcp laughing_pike

# from the returned information, you can see that the listening port 5000 in the container is mapped to the local port 1024. Let's try to access the local port 1024.

Curl http://127.0.0.1:1024/

# return

Hello world!

Enter the container environment

The above example is to access the container externally. Let's try to enter the container environment to see the specific situation.

# View the list of currently running container instances

Docker ps-a

# return information

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

5da522ffe229 training/webapp "python app.py" 8 minutes ago Up 8 minutes 0.0.0.0 minutes ago Up 1024-> 5000/tcp laughing_pike

# the container instance ID we want to enter is 5da522ffe229

# using exec commands and running bash,-it at the same time is an interactive command terminal

Docker exec-it 5da522ffe229 / bin/bash

# after running, we will find that the command line terminal has changed and entered into the instance 5da522ffe229

Root@5da522ffe229:/opt/webapp#

# run netstat to see if you are listening

Netstat-lnp

# see, the webapp we ran earlier listens on the internal port of 5000

Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name

Tcp 00 0.0.0.0 5000 0.0.0.0 * LISTEN-

# We try to access port 5000 and prompt bash: curl: command not found

# because we have entered the isolated environment of the container and have not installed curl yet

Curl http://127.0.0.1:5000/

# Let's install curl first

Apt-get update; apt install-y curl

# run again after the installation is successful

Curl http://127.0.0.1:5000/

# the information can be returned successfully this time

Hello world!

# exit the current container environment, and the command line prompt has returned to the local machine

Ctrl+d

Other usage features

# View the log log of the specified container instance

Docker logs-f 5da522ffe229

# View the top of the specified container instance

Docker top 5da522ffe229

# View the port information of the specified container

Docker port 5da522ffe229

# View the configuration information of the specified container

Docker inspect 5da522ffe229

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Ruijiangyun official website link: https://www.eflycloud.com/home?from=RJ0035

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