Docker introduction

What is Docker?

When people say "Docker", they usually refer to Docker Engine, which is a client server application, which is controlled by Docker
A daemon, a REST API that specifies the interface to interact with the daemon, and a command line interface (CLI) to communicate with the daemon (by encapsulating the REST API). The Docker Engine receives docker commands from the CLI, such as docker run, docker ps to list running containers, docker images to list images, and so on.

• docker is a software that can run on window s, linux, mac and other operating systems.
• docker is an open source application container engine. It is developed based on Go language and complies with Apache 2.0 protocol. The project code is entrusted to
  Tube maintenance on github
• docker allows developers to package their applications and dependent packages into a lightweight and portable container, and then publish them to anyone
  On popular Linux machines.
• Containers completely use sandbox mechanism, and there will be no interface between them. More importantly, the performance overhead of containers is very low.

Basic composition of Docker

• Docker host: the machine on which the docker program is installed (docker is directly installed on the operating system);
• docker repository (Registry): used to store various packaged software images; Warehouses are divided into public warehouses and private warehouses. (very similar)
  maven)
• Docker images: images packaged by software; placed in docker warehouse;
• docker container: the instance after the image is started is called a container; a container is an application or group of applications running independently

Comparison between Docker and operating system

Docker is a lightweight virtualization method. The characteristics of docker compared with traditional operating system technology are as follows:

characteristic	container	virtual machine
Starting speed	Second order	Minute level
performance	Near primary	Weaker
Memory cost	Very small	More
Hard disk usage	Typically MB	Generally GB
Operating density	A single machine supports thousands of containers	Generally dozens
Isolation	Safety isolation	Complete isolation
Mobility	excellent	commonly

The traditional virtual machine provides relatively closed isolation. Docker uses a variety of protection technologies on Linux system to achieve strict isolation
Since version 1.3.0, docker has focused on improving the security control and mirroring of containers
The security mechanism greatly improves the security of using docker.

Docker version

After version 17.03, docker is divided into CE (Community Edition) and EE (Enterprise Edition)
This tutorial uses the Community Edition (CE).

Advantages of Docker

One product: development – launch two sets of environments! Application environment, application configuration! Development – operation and maintenance. Problem: I can allow it on my computer! Version update makes the service unavailable! It is a great test for operation and maintenance!!! Environment configuration is very troublesome, and each machine needs to deploy the environment (cluster Redis, ES, Hadoop...) ! it's a lot of trouble. If you publish a project (jar + (Redis MySQL JDK ES)), can the project be installed and packaged with the environment! It's too troublesome to configure an application environment Redis MySQL JDK ES Hadoop on the server before
And can't cross platform.

• Development environment Windows, finally released to Linux!
  Tradition: development jar, operation and maintenance to do!
  Now: development, packaging, deployment and launch, and a set of processes are completed!

• Faster delivery and deployment of applications
  Traditional: help documentation, setup.
  Docker: the packaged image publishing test runs with one click.

• More convenient upgrade and capacity expansion
  After using Docker, we deploy applications just like building blocks
  The project is packaged as an image to expand server A and server B

• Simpler system operation and maintenance
  After containerization, our development and test environments are highly consistent

• More efficient utilization of computing resources
  Docker is kernel level virtualization, which can run many container instances on a physical machine! The performance of the server can be squeezed to the extreme

Docker installation

Docker official website

docker official website address:
https://www.docker.com

docker official document address:
https://docs.docker.com/

Alibaba cloud Developer Platform official website address:
(you can refer to the docker installation tutorial provided on Alibaba cloud's official website for installation.)
https://developer.aliyun.com/article/110806

Hardware requirements for installation

When we install Docker, two main components will be involved:

• Docker CLI: client
• Docker daemon: sometimes called "server" or "engine"

docker hardware installation should meet the following conditions:

Serial number	Hardware	requirement
1	CPU	More than 2 cores are recommended
2	Memory	At least 2G
3	Hard disk	At least 50G
4	system	docker and K8S clusters recommend that you use CentOS 7.8

System configuration of centos virtual machine

• View centos system version command:

cat /etc/centos-release

• Configure Alibaba cloud yum source

#Download and install wget
yum install -y wget

#Backup default yum
mv /etc/yum.repos.d /etc/yum.repos.d.backup

#Set new yum directory
mkdir -p /etc/yum.repos.d

#Download Alibaba yum configuration to this directory and select the corresponding version
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

#Update the epel source to Alibaba cloud epel source
mv /etc/yum.repos.d/epel.repo /etc/yum.repos.d/epel.repo.backup
mv /etc/yum.repos.d/epel-testing.repo /etc/yum.repos.d/epel-testing.repo.backup
wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo

#Rebuild cache
yum clean all
yum makecache

#Let's see how many bags there are in the warehouse
yum repolist

• Upgrade system kernel

rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
yum --enablerepo=elrepo-kernel install -y kernel-lt
grep initrd16 /boot/grub2/grub.cfg 
grub2-set-default 0

reboot

• View system kernel commands

uname -r
uname -a

• View CPU commands

lscpu

• View memory commands

free
free -h

• View hard disk information

fdisk -l

• Turn off firewall

systemctl stop firewalld
systemctl disable firewalld

• Close selinux

sed -i 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux
setenforce 0

• Bridge filtering

vi /etc/sysctl.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-arptables = 1
net.ipv4.ip_forward=1
net.ipv4.ip_forward_use_pmtu = 0

#Effective order
sysctl --system

• Open command completion

#Installing bash completion
yum -y install bash-completion bash-completion-extras

#Using bash completion
source /etc/profile.d/bash_completion.sh

• Upload file function

yum -y install lrzsz
#1. Drag the mouse to upload the file
#2. Download files
#2.1 download a file
     sz filename
#2.2 downloading multiple files
     sz filename1 filename2
#2.3 download all files in dir directory, excluding folders in dir
     sz dir/*

Installation of Docker

# step 1: install some necessary system tools
sudo yum install -y yum-utils device-mapper-persistent-data lvm2
# Step 2: add software source information
sudo yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
# Step 3: update and install docker CE
sudo yum makecache fast
sudo yum -y install docker-ce
# Step 4: start Docker service
sudo service docker start

Note: other considerations are in the notes below
# The official software source enables the latest software by default. You can obtain the software packages of various versions by editing the software source. For example, the official does not make the software source of the test version available, you can open it in the following ways. Similarly, you can open various test versions, etc.
# vim /etc/yum.repos.d/docker-ce.repo
#   Change enabled=0 under [docker CE test] to enabled=1
#
# Install the specified version of docker Ce:
# Step 1: find docker CE version:
# yum list docker-ce.x86_64 --showduplicates | sort -r
#   Loading mirror speeds from cached hostfile
#   Loaded plugins: branch, fastestmirror, langpacks
#   docker-ce.x86_64            17.03.1.ce-1.el7.centos            docker-ce-stable
#   docker-ce.x86_64            17.03.1.ce-1.el7.centos            @docker-ce-stable
#   docker-ce.x86_64            17.03.0.ce-1.el7.centos            docker-ce-stable
#   Available Packages
# Step 2: install the specified version of docker Ce: (version, for example, 17.03.0.ce.1-1. EL7. CentOS above)
# sudo yum -y install docker-ce-[VERSION]
# Note: after some versions, other dependent packages appear in docker CE installation. If the installation fails, please pay attention to the error information. For example, after docker CE 17.03, you need to install docker CE SELinux first.
# yum list docker-ce-selinux- --showduplicates | sort -r
# sudo yum -y install docker-ce-selinux-[VERSION]

# When installing through classic network and VPC network intranet, replace the command in Step 2 with the following command
# Classic network:
# sudo yum-config-manager --add-repo http://mirrors.aliyuncs.com/docker-ce/linux/centos/docker-ce.repo
# VPC network:
# sudo yum-config-manager --add-repo http://mirrors.could.aliyuncs.com/docker-ce/linux/centos/docker-ce.repo

Install alicloud image accelerator

The image accelerator can speed up the download of docker image. Whether it is installed or not depends on your mood

mkdir -p /etc/docker
tee /etc/docker/daemon.json <<-'EOF'
{
"registry-mirrors": ["https://Copy your accelerator address. mirror.aliyuncs.com "]
}
EOF
systemctl daemon-reload
systemctl restart docker

docker command

docker command classification

This chapter records the use of docker commands in most situations. If you want to know the details of each option, please refer to the official documents according to the case on docker's official website.

docker official website address: https://docs.docker.com/engine/reference/run/

Generally speaking, it can be divided into the following categories:

#docker environment information
docker -v
docker info
docker version

#Container lifecycle management
docker [create|exec|run|start|stop|restart|kill|rm|pause|unpause]

#Container operation management
docker [ps|inspect|top|attach|wait|export|port|rename|stat]

#Container rootfs command
docker [commit|cp|diff]

#Mirror warehouse
docker [login|pull|push|search]

#Local image management
docker [build|images|rmi|tag|save|import|load]

#Container resource management
docker [volume|network]

#System log information
docker [events|history|logs]

Starting from the docker command, sort out the following structure diagram: