Docker Container (container) - 6

Table of contents:

1. What is a container?
2. Container life case?
3. Why do you need containers?
4. Container life cycle
   1. Container OOM
   2. Container exits abnormally
   3. Container paused
5. Container command list
6. Detailed explanation of container commands
   1. docker create
   2. docker run
   3. docker ps
   4. docker logs
   5. docker attach
   6. docker exec
   7. docker start
   8. docker stop
   9. docker restart
   10. docker kill
   11. docker top
   12. docker stats
   13. docker container inspect
   14. docker port
   15. docker cp
   16. docker diff
   17. docker commit
   18. docker pause
   19. docker unpause
   20. docker rm
   21. docker export
   22. docker wait
   23. docker rename
   24. docker container prune
   25. docker update
7. Container operation case
   1. Basic container operations
   2. Container state migration
   3. Container batch processing tips
   4. Container interaction mode
      1. attached mode
      2. detached mode
      3. interactive mode
   5. Container and host content replication
   6. Container automatically deleted
   7. Container automatically restarts
   8. Container environment variable settings
   9. View container details
   10. Container executes single line command
   11. Container image import and export
   12. View container logs
   13. Container resource view
8. Comprehensive actual combat 1. Mysql containerized installation
9. Comprehensive actual combat 2. Redis containerized installation
   1. The reason for the emergence of Redis
   2. What is Redis
   3. Redis application scenarios
   4. Redis life case
   5. Redis container creation
10. Comprehensive practical practice three, C++ container production
    1. what is the source
    2. What is mirroring
    3. Mirror source
    4. Dayuan of Science and Technology of China
    5. Make a c++ container
11. Comprehensive practical experience 4. SpringBoot container production
12. Comprehensive actual combat 5. Container resource update

1. What is a container?

In layman's terms, a container is the running entity of an image. The image is a static read-only file, while the container has a writable file layer required at runtime, and the process in the container is in a running state. That is, the container runs the real application process. Containers have five states: initially created, running, stopped, paused, and deleted. Although the essence of a container is a process running on the host, the container has its own independent namespace isolation and resource limitations. In other words, inside the container, you cannot see the processes, environment variables, network and other information on the host. This is the essential difference between the container and the process running directly on the host. A container is a runnable instance created based on an image and exists independently. One image can create multiple containers. When running a containerized environment, a read-write copy of this file system is actually created inside the container. This will add a container layer that allows modification of the entire copy of the image

2. Container life cases?

Mirrors and containers are equivalent to rough houses provided by developers, but the decorations of the two families are completely different. Or we have all learned object-oriented languages ​​​​such as Java or C++. It can be understood that the image is the basic class, and the container is an object instantiated. The content inside will be different unless the user needs it.

3. Why do we need containers?

The image is a static file and cannot provide services, just like I took a Linux or Windows CD. Only when it is installed on the host and run can it provide external services and we can use it. What benefits do containers bring? Please refer to our previous explanation of why virtualization and containerization are necessary.
 

4. Container life cycle

A container's lifecycle is the possible states the container may be in.

1. 1created：Initially created state
2. running: running status
3. stopped: stopped state
4. paused: paused state
5. deleted: deleted status

The conversion relationship between each life cycle is shown in the figure:

• docker create: After creating the container, it does not start running immediately, and the container enters the initial construction state;
• docker run: Create a container, start running immediately, and enter the running state;
• docker start: Container changes to running state;
• docker stop: The container will enter the stopped state;
• docker kill: When the container fails (crash), execute kill (power off), and the container will enter the stopped state. This
• The operation is easy to lose data, so it is not recommended to use it unless necessary;
• docker restart: Restart the container and the container enters the running state;
• docker pause: The container enters the paused state;
• docker unpause: Cancel the pause state and the container enters the running state;
• docker rm: Delete the container and the container enters the deleted state.
• Killed by out-of-memory (terminated due to insufficient memory): The host memory is exhausted, also known as OOM: unplanned termination. At this time, the container that consumes the most memory needs to be killed.
• Container process exitde (abnormal termination): After the container is terminated, the Should restart? selection operation will be entered:
  • yes needs to be restarted, and the container executes the start command to enter the running state.
  • no does not require restarting, the container will enter the stopped state.​ 

Container OOM

Docker is divided into three situations when handling OOM events

• An OOM event is triggered if an application in a container exhausts the memory quota allocated to the container by the host system. For example, in a container, a web service is deployed. Assume that the upper limit of memory allocated by the host to this container is 1G. When the memory requested by the script is greater than 1G, this container will trigger an OOM event. In this case, the container will be forced to close. However, it should be noted that it is not the Docker Daemon that closes the container at this time, but the host operating system. Because a container is actually a group of processes running in the host operating system. The host operating system sets resource limits for this group of processes through cgroups. When the resources requested by these processes reach the upper limit, the host operating system triggers Kernel OOM events, so it is ultimately the host kernel that shuts down these processes.
• If the user does not want to close the container, they can select --oom-kill-disable to disable OOM-Killer. When using this parameter, you still need to pay attention. If you use -m to set the memory upper limit of this container, then when the container reaches the upper limit of memory resources, the host will not shut down the container, but it will not continue to allocate resources to this container. At this time, the container will be in hung state. It is only necessary to contain the worst-case scenario within a certain range and prevent it from spreading.
• If the user uses --oom-kill-disable but does not use -m to set the upper limit, the container will use as much host memory resources as possible. In other words, the host will use as much memory as it has.

Container exits abnormally

There is an Init process inside each container, and all other processes in the container are children of this process. The running container is because the Init process is running. If a child process exits for some reason, its parent process will also exit synchronously until the Init process also exits. When the Init process exits, it means that the container is closed. Ocker currently has no way of knowing whether the process exit at this time is a normal exit or an abnormal exit. When a container is shut down, the Docker Daemon will try to change the container from the Stopped state to the Running state again. Only containers with the --restart parameter set will be attempted by Docker Daemon, otherwise the container will remain stopped.

Container paused

Docker "robbed" this container of CPU resources. Other resources, such as Memory resources, Network resources, etc., remain untouched. As a result, the process that has lost CPU resources will not be scheduled by the host kernel system, so the container is in a "frozen" state.
 

5. Container command list

6. Detailed explanation of container commands

docker create

Function

Create a new container but don't start it

grammar

docker create [OPTIONS] IMAGE [COMMAND] [ARG...]

Alias

docker container create

key parameter

• -i: Run the container in interactive mode, usually used together with -t;
• -P: Random port mapping, the container’s internal port is randomly mapped to the host’s port
• -p: Specify port mapping, the format is: host (host) port: container port
• -t: Reassign a pseudo input terminal to the container, usually used together with -i;
• --name="nginx-lb": Specify a name for the container;
• -h "mars": Specifies the hostname of the container;
• -e username="ritchie": Set environment variables;
• --cpuset-cpus="0-2" or --cpuset-cpus="0,1,2": Bind the container to the specified CPU to run;
• -m: Set the maximum memory used by the container;
• --network="bridge": Specifies the network connection type of the container;
• --link=[]: Add a link to another container;
• --volume, -v: Bind a volume
• --rm :shell automatically deletes the container when exiting
• --restart: Automatically restart

Sample

docker create --name mynginx nginx:latest

docker run

Function

Create a new container and run a command

grammar

docker run [OPTIONS] IMAGE [COMMAND] [ARG...]

Alias

docker container run

 key parameter

• -d: Run the container in the background and return the container ID; this parameter is more than create
• -i: Run the container in interactive mode, usually used together with -t;
• -P: Random port mapping, the container’s internal port is randomly mapped to the host’s port
• -p: Specify port mapping, the format is: host (host) port: container port
• -t: Reassign a pseudo input terminal to the container, usually used together with -i;
• --name="nginx-lb": Specify a name for the container;
• -h "mars": Specifies the hostname of the container;
• -e username="ritchie": Set environment variables;
• --cpuset-cpus="0-2" or --cpuset-cpus="0,1,2": Bind the container to the specified CPU to run;
• -m: Set the maximum memory used by the container;
• --network="bridge": Specifies the network connection type of the container;
• --link=[]: Add a link to another container;
• --volume, -v: Bind a volume
• --rm :shell automatically deletes the container when exiting
• --restart: Automatically restart
   

Sample

docker ps

Function

list containers

grammar

docker ps [OPTIONS]

Alias

docker container ls, docker container list, docker container ps

key parameter

• -a: Display all containers, including those that are not running.
• -f: Filter the displayed content based on conditions.
• --format: Specify the template file for the return value. Such as json or table
• -l: Display the latest container.
• -n: List the n most recently created containers.
• --no-trunc: Do not truncate output.
• -q: Silent mode, only the container number is displayed.
• -s: Display the total file size.

Sample

docker ps -a

docker logs

Function

View container logs

grammar

docker logs [OPTIONS] CONTAINER

Alias

docker container logs

key parameter

-f,--follow: Track log output
--since: Display all logs at a certain start time
-t,-- timestamps: display timestamps
-n, --tail: list only the latest N container logs

Sample

docker attach

Function

Connect to a running container.

grammar

docker attach [OPTIONS] CONTAINER

Alias

docker container attach

key parameter

--sig-proxy: Whether to proxy all signals. The default is true. If set to false, exiting will not affect the container. Otherwise, exiting will cause the container to exit.

Sample

 

The message is displayed as

• CONTAINER ID: Container ID.
• IMAGE: The image used.
• COMMAND: The command to run when starting the container.
• CREATED: The creation time of the container.
• STATUS: Container status.
• PORTS: The port information of the container and the connection type used (tcp\udp).
• NAMES: Automatically assigned container names.

docker exec

Function

Execute command in container

grammar

docker exec [OPTIONS] CONTAINER COMMAND [ARG...]

Alias

docker container exec

key parameter

• -d: Detached mode: run in the background
• -i : Keep STDIN open even if not attached
• -t: allocate a pseudo terminal
• -e: Set environment variables
• -u,--user: Specify user "<name|uid>[:<group|gid>]"
• -w,--workdir: Specify the working directory

Sample

#在容器 mynginx 中以交互模式执行 echo:
docker exec -it mynginx echo "Hello world"
#在容器 mynginx 中以交互模式打开 shell:
docker exec -it mynginx bash
#通过 id 进去， docker ps 可以看到容器 id
docker exec -it 5706674cc67e bash

docker start

Function

Start a stopped container

grammar

docker start [OPTIONS] CONTAINER [CONTAINER...]

Alias

docker container start

Sample

docker start mynginx

docker stop

Function

Stop a running container

grammar

docker stop [OPTIONS] CONTAINER [CONTAINER...]

Alias

docker container stop

key parameter

-s: signal sent

Sample

docker stop mynginx

docker restart

Function

Restart container

grammar

docker restart [OPTIONS] CONTAINER [CONTAINER...]

Alias

docker container restart

key parameter

 -s: send signal

Sample

docker restart mynginx

docker kill

Function

Force quit container

grammar

docker kill [OPTIONS] CONTAINER [CONTAINER...]

Alias

docker container kill

key parameter

-s: signal sent

Precautions:

Docker stop sends the SIGTERM signal, and docker kill sends the SIGKILL signal.

Sample

docker kill mynginx

docker top

Function

View process information running in the container, supports ps command parameters.

grammar

docker top CONTAINER [ps OPTIONS]

Alias

docker container top

Precautions

There may not be a /bin/bash terminal to interactively execute the top command when the container is running, and the container may not have the top command. You can use docker top to view the processes running in the container.

Sample

#查看容器进程信息
docker top mynginx

docker stats

Function

Displays the usage of container resources, including: CPU, memory, network I/O, etc.

grammar

docker stats [OPTIONS] [CONTAINER...]

Alias

docker container stats

key parameter

• --all, -a: Display all containers, including those that are not running.
• --format: Specify the template file for the return value. Such as table, json
• --no-stream: Display the current status and exit directly, no longer updating in real time.
• --no-trunc: Do not truncate output.

Return message

• CONTAINER ID and NAME: Container ID and name.
• CPU % and MEM %: The percentage of CPU and memory used by the container.
• MEM USAGE / LIMIT: The total memory being used by the container, and the total amount of memory allowed to be used.
• NET I/O: The amount of data sent and received by a container through its network interface.
• BLOCK I/O: The amount of data the container reads and writes from block devices on the host.
• PIDs: The number of processes or threads created by the container.

Sample

docker container inspect

Function

View container details

grammar

docker container inspect [OPTIONS] CONTAINER [CONTAINER...]

key parameter

• -f: Specifies the template file for the return value. Such as table, json
• -s: Display the total file size.

Precautions:

• docker inspect will automatically check whether it is an image or a container and then display the trust information

Sample

docker container inspect mynginx

docker port

Function

Used to list port mappings for a specified container, or to find a PRIVATE_PORT NAT to a public-facing port.

grammar

docker port CONTAINER [PRIVATE_PORT[/PROTO]]

Alias

docker container port

Sample

docker port mynginx

docker cp

Function

Copy files between container and host

grammar

docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH|-
docker cp [OPTIONS] SRC_PATH|- CONTAINER:DEST_PATH

Alias

docker container cp

Sample

#将主机/www/目录拷贝到容器 mynginx 的/www 目录下。
docker cp /www/ mynginx:/www/
#将容器/www/目录拷贝到主机的/wwwbak 目录下。
docker cp mynginx:/www/ /wwwbak/

docker diff

Function

Check for changes to the file structure in the container.

grammar

docker diff CONTAINER

Sample

docker diff mynginx

docker commit

Function

Create a new image from the container.

grammar

docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]

parameter

• -a: The submitted image author;
• -c: Use Dockerfile instructions to create the image; you can modify the startup instructions
• -m: Description text when submitting;
• -p: Pause the container when committing.

Sample

docker commit c3f279d17e0a maxhou/mynginx:v01

docker pause

Function

Pause all processes in the container.

grammar

docker pause CONTAINER [CONTAINER...]

Alias

docker container pause

Sample

docker pause mynginx

docker unpause

Function

Restore all processes in the container

grammar

docker unpause CONTAINER [CONTAINER...]

Alias

docker container unpause

Sample

docker unpause mynginx

docker rm

Function

Remove stopped containers

grammar

docker rm [OPTIONS] CONTAINER [CONTAINER...]

Alias

docker container rm

key parameter

-f: Forcefully delete a running container through the SIGKILL signal

Sample

#删除 mynginx 容器
docker stop mynginx
docker rm mynginx
#删除所有停止的容器
docker rm $(docker ps -a -q)

docker export

Function

Export container contents as tar file

grammar

docker export [OPTIONS] CONTAINER

Alias

docker container export

key parameter

-o: Write to file.

Sample

#导出 nginx 为 tar
docker export -o mynginx202203.tar mynginx

docker wait

Function

Blocks the run until the container stops, then prints out its exit code.

grammar

docker wait CONTAINER [CONTAINER...]

Alias

docker container wait

Sample

docker wait mynginx

docker rename

Function

double naming container

grammar

docker rename CONTAINER NEW_NAME

Alias

docker container rename

Sample

docker rename mynginx myweb

docker container prune

Function

Remove all stopped containers

grammar

docker container prune [OPTIONS]

key parameter

-f, --force: Do not prompt for confirmation

Sample

docker container prune

docker update

Function

Update container configuration

grammar

docker update [OPTIONS] CONTAINER [CONTAINER...]

Alias

docker container update

key parameter

• --cpus: cpu number
• --cpuset-cpus : Which cpu to use
• --memory :memory limit
• --memory-swap: swap memory
• --cpu-period: is used to specify how long the container's use of the CPU should be reallocated. 
• --cpu-quota: is used to specify the maximum amount of time that can be used to run this container during this cycle.

Sample

#更新内存
docker update -m 400m myweb

7. Container operation cases

Basic container operations

Create a container through nginx image file

List of containers (including running containers)

 

Stop the currently running container

 

List of containers (including running and exited containers)

 

Container deletion

  

Container state migration

First we create the container

Through docker ps we can see that the container status is created

 

Start the container through docker start

You can see that the container is running through docker ps

 

Containers can be stopped via docker stop

 

Start the container again and kill the container

 

Start the container, then pause the container

 

restore container

Restart the container and you can see that the startup time of the container has become shorter.

 

Containers can be deleted through docker rm

Container batch processing tips

• -a: Indicates printing all container information, including running and exited containers
• -q: indicates that only the container ID is returned
• -f: indicates filtering based on the given conditions. Equivalent to the --filter option.

 

 

Note: Other commands can also be compared when doing batch processing, such as batch stop docker containerstop $(docker container ps -aq)

Container interaction mode

attached mode

• -p 80:80 represents port mapping. The first port represents the port mapped to the host, and the second port represents the port mapped to the Docker container. This will be explained in detail in the network chapter.
• Creating a container through the above method is in attached mode, so that the container will run in the foreground.
• When accessing the server URL, the command window will print a log every time it is accessed. The logs of the Docker container will be displayed in the window in real time and occupy this port.
• If you are on a Linux server, pressing Ctrl+C will stop the Docker service. It is easy to misoperate, so we need a better and more stable mode, which corresponds to the detached mode.
• attached mode is only applicable to the debugging phase of containers and programs
• Let’s practice the usage of attached mode
• Step 1: Create a running container in attached mode and map it to port 80 of the host

 

• Step 2: Access port 80 of the server, use a browser to access the server IP or domain name, access port 80 by default

 

You can see that the nginx homepage has been displayed on the browser. When we refresh the access, we find that some relevant logs will be printed on the standard output.

Step 3: Type Ctrl + C

 

detached mode

• Add a -d or --detach option to the docker container run -p 80:80 nginx command to indicate detached mode, that is, execute in the background
• Runs in the background, only the container ID is displayed after startup, and any command can be entered
• Even if the window is closed, it will continue to run. To stop and delete the container, you need to use shell commands, which reduces a lot of misoperations.
• It is recommended to use attached mode instead of
• Let’s practice the usage of detached mode
• Step 1: Create a container in detached mode and map port 80

  

•  Step 2: Visit the server URL with the browser and check the background log

 

• Refresh the browser and you can see that the relevant logs have been printed in the background.

 

Dynamic tracking log: The background log window will only print the log once. If you want to dynamically track the log, you can add the -f
option; if you want to turn off the log tracking mode, you can type Ctrl+C to end

Convert detached mode to attached mode

 

interactive mode

After we create a container, we may need to get some information or execute some commands inside the container, and we need to enter interactive mode. For example, after creating an Ubuntu container, if you need to enter various Shell commands into the system to interact with the system, you need to enter the interactive mode.

Create a running container and enter interactive mode

 -i: Keep the container running. Usually used together with -t. After adding the two parameters it, the container will automatically enter the container after it is created. After exiting the container, the container will automatically close
-t: Reassign a pseudo input terminal to the container , usually used together with -i
to enter interactive mode for an already running container

Exit interactive mode: Enter exit in an interactive shell

  

Container and host content replication

We start an nginx service

 Compile an index.html file on the host machine

Copy host files to the container

Enter the container to view

Container automatically deleted

To start an nginx, we specify the --rm option

Stop container

 

Check again whether the container exists and find that the container has been automatically deleted.

Container automatically restarts

Container restart options are as follows:

• docker run --restart=no [container name]: The default value is not to restart automatically
• docker run --restart=on-failure:3 [container name] : on-failure If the exit status of the container is not 0, then
• Docker automatically restarts the container, and you can also specify the number of restarts. If the container fails to start more than the specified number of times, it will give up.
• docker run --restart=always [container name] :always always restarts the container when it exits
• docker run --restart=unless-stopped [container name] unless-stopped The container always restarts when it exits.
• However, containers that have been stopped when the Docker daemon is started are not considered.
• If the –restart parameter is not set when the container is started, update it with the following command:
• docker update --restart=always [container name]
   

Start the nginx service and specify to always restart

 

Enter the nginx service and kill to start the process

Check the process status to see whether the process is still in startup status

  

free up space

Container environment variable settings

Start an nginx container, configure environment variables, TEST=1

Enter the container to view environment variables

 

clear space

Configure environment variables through the configuration file:

  

View container details

We can view the detailed information of a container, for example, we can view all set environment variables

Start container

View container information

 

Release resources 

Container executes single line command

We can directly use the docker container environment to execute some commands. For example, when there is a certain command in the container but not on the host, we can use the container to complete certain tasks.

Container image import and export

We create a directory and edit a custom homepage

Enter the following content on the homepage

 

We run an nginx image and then modify the homepage through docker cp

 

What you see when you visit the homepage is as follows:

We save the image through docker export

We import the image through docker import

 

Stop our current container and restart the container

Start a new container using the exported image

 

If you use import to import the file generated by export, although the import will not prompt an error, it will prompt a failure when starting the container, and an error similar to "docker: Error response from daemon: Container command not found or does not exist" will appear. We have to specify the startup command. Because export loses metadata information.
 

View container logs

Start an nginx

View all logs

 

View logs in real time

 

Refresh the page visited several times

 

View logs in real time

 

View the latest 3 lines of logs

 

Stop the container to release resources

  

Container resource view

We run an nginx

We can use docker top to see which processes are in the container. By adding aux, we can see the occupied memory and CPU information.

 

You can see real-time resource usage changes through docker stats

Release resources

 

8. Comprehensive actual combat 1. Mysql containerized installation

Enter the mysql mirror website and find the mysql mirror

You can see that there are so many tags

We choose the most used version 5.7 to pull the image

 

We know that the default port of msyql is 3306 and has a password. Check the official website's startup case docker run --name some-mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql:tag specifies the password information of mysql

We enter the container login and we can see that we can log in to msyql normally.

 

If we open port 8200 to the outside world and there is no firewall, we can remotely log in to the interface through the GUI tool. Take mysql workbench as an example.

 

free up space

 

9. Comprehensive actual combat 2. Redis containerized installation

The reason for the emergence of Redis

In the early days of the development of Web applications, relational databases received widespread attention and application. The reason was that at that time, Web sites basically had low access and concurrency, and there were few interactions. Later, as the number of visits increased, Web sites using relational databases began to experience some bottlenecks in performance, and the source of the bottleneck was generally disk I/O. With the further development of Internet technology, various types of applications emerge in endlessly, which has led to more demand for performance in today's era of cloud computing and big data, which is mainly reflected in the following aspects:

1. Low-latency read and write speed: rapid application response can greatly improve user satisfaction
2. Support massive data and traffic: for large-scale applications such as search It requires the use of petabytes of data and the ability to handle millions of traffic

In order to overcome this problem, NoSQL came into being. It has the advantages of high performance, strong scalability, and high availability, and is favored by a wide range of developers and warehouse managers.

What is Redis

The full name of Redis is Remote Dictionary Server, and its Chinese name is Remote Dictionary Server.

Redis is one of the most popular NoSQL databases now. Redis is an open source, written in ANSI C, containing a variety of data structures, supporting network, memory-based, optional persistence key-value pair storage database. It has
the following characteristics:

Based on memory operation, high performance
Supports distribution, theoretically infinite expansion
key-value storage system
Open source is written in ANSI C language, complies with the BSD protocol, supports the network, can be memory-based and persistent log-type, Key-Value database, and provides APIs in multiple languages

Redis application scenarios

Almost all major manufacturers are using Redis. Redis provides a variety of data types, such as String type, hash type, list type, collection type and sequential collection type. With these types, various applications can be easily implemented, such as caching system ("hot" data: high-frequency reading, low-frequency write), counters, message queue systems, real-time leaderboards, social networks.

Redis life case

Redis is like a Xinhua dictionary, which can quickly find the corresponding word in the dictionary based on a certain character.

Redis container creation

Download redis image

Start the redis container

 

 Enter the container and set a key

If the firewall is enabled, we can connect through the visual tool, the visual tool download address
 AnotherRedisDesktopManager release version - Gitee.com

 

Configure link

 

View key

 

Exit the container and free up space

 

10. Comprehensive practical practice three, C++ container production

what is the source

The source is the source.
This is where the program gets the software package from when you install the software (the installation program is on your machine, but the things that need to be installed are on the software source server).
Source, under Ubuntu, it is equivalent to a software library. What software is needed? Just remember the correct software name and you can install it with the command:
In fact, you can Call it a software warehouse. When you install the software, you retrieve the data from the warehouse and put it on your machine.
 

sudo apt-get install software name

For example: if you want to install the gcc software, you can enter sudo apt-get install gcc in the terminal, which will help you install the gcc software. If the software is not in the source, this command cannot be completed.
 

What is mirroring

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 a mirror.
Common image file formats include ISO, BIN, IMG, TAO, DAO, CIF, and FCD.
The so-called image file is actually similar to a ZIP compressed package. It makes a specific series of files into a single file in a certain format to facilitate users to download and use, such as a test version of the operating system. , games, etc. (Those who have installed operating systems should be familiar with xxx.iso) Image files not only have the "synthesis" function of ZIP compressed packages, but their most important feature is that they can be recognized by specific software and can be burned directly to a disc.

Mirror source

The mirror source is to make a mirror of the official source. You can download the software here. For example, if the official source of Ubuntu is abroad, downloading the software may be very slow. In this case, you need to switch to a domestic mirror source. We make a C++ container based on ubuntu. When running the output, HelloWorld can use the image source as an agent. For example, when buying a car, I originally had to go to a car factory, but after setting up 4S stores, I can just go to the 4S store instead of going to the car factory.

Dayuan of Science and Technology of China

https://mirrors.ustc.edu.cn/help/

Make a c++ container

Download the Ubuntu image

Start container

 

Configure domestic image source acceleration

 Install gcc vim

Edit code

Compile code

 

Run in container

 

Exit container

 

At this time, you can see that our container has exited. If we want to enter again, we can use docker restart to restore the container.
 

Clean up containers to free up space

 

11. Comprehensive practical experience 4. SpringBoot container production

Write a demo

Use Spring Boot to create a simple demo and output hello docker! in the browser.

Create a maven project and select the first release version 2.0.2.RELEASE of Spring Boot 2.x for explanation. Add the spring-boot dependency in pom.xml as follows

 

Write the main function to build the Spring container

 

Write a controller

 

Use maven packaging to generate jar packages

 

The generated jar package is located in the target directory under the project root path

Test whether the jar package is available

 

 After starting the container, visit localhost:8080/hello to view the running results and confirm that the jar package is available.

Upload to Linux server for backup

 

Make a container

Download the Ubuntu image

 

Start container

 Configure domestic image source acceleration

Install jdk

Open a new shell window and copy the jar into the container

 

 View files in the container

Start java service

 

Access the page through a browser, making sure the firewall is turned on

 

ctrl+c exits the service, exit exits the container

Release resources

12. Comprehensive actual combat 5. Container resource update

We run an nginx

We can use docker top to see which processes are in the container. By adding aux, we can see the occupied memory and CPU information.

 

You can see the dynamic changes of resources through docker stats

 

We update the maximum memory of docker through docker update

 

We check again through docker stats and see that the memory has been limited to 300m.

 

We execute a command in the container to fill up the cpu

for i in `seq 1 $(cat /proc/cpuinfo |grep "physical id" |wc -l)`
do
dd if=/dev/zero of=/dev/null &
done
#说明：
#cat /proc/cpuinfo |grep “physical id” | wc -l 可以获得 CPU 的个数,
我们将其表示为 N
#seq 1 N 用来生成１到Ｎ之间的数字
#for i in seq 1 N; 就是循环执行命令,从１到Ｎ
#dd if=/dev/zero of=/dev/null 执行 dd 命令, 输出到/dev/null, 实际上
只占用 CPU, 没有 IO 操作
#由于连续执行Ｎ个(Ｎ是 CPU 个数)的 dd 命令, 且使用率为 100%, 这时调度器
会调度每个 dd 命令在不同的 CPU 上处理，最终就实现所有ＣＰＵ占用率 100%

Executing command configuration can only use 10% of the cpu

 

You can see that the CPU has only reached about 10%.

 

 Stop the container and release resources

13. Frequently Asked Questions

What is the difference between docker create, docker start and docker run?

The docker create command creates a brand new container from a Docker image. However, it won't run it immediately. The docker start command will start any stopped containers. If you created a container using the docker create command, you can use this command to start it.
The docker run command is a combination of create and start because it creates a new container and starts it immediately. In fact, if the docker run command cannot find the above image on your system, it can pull the image from Docker Hub.
 

What is the difference between docker import and docker load?

To understand the difference between docker load and docker import commands, you must also know docker save and docker export commands:

• docker images save_name: Export an image as a file, and then use the docker load command to import the file as an image. All historical records of the image will be saved. It is larger than the file exported by the docker export command and is easy to understand because all the history of the image will be saved.
• docker export container_id: Export a container as a file, and then use the dockerimport command to import the container into a new image. However, compared to the docker save command, the container file will lose all metadata and history, and only saves the current state of the container, which is quite for virtual machine snapshots. You can use the docker load command to import the image library storage file to the local image library, or you can use the docker import command to import a container snapshot into the local image library.
• The difference between the two is that container snapshots will discard all historical records and metadata information, while image storage files will save complete records and will be larger in size.

What is the difference between docker rm & docker rmi & docker prune?

• docker rm: delete one or more containers
• docker rmi: delete one or more images
• docker prune: used to delete docker objects that are no longer used