Docker系列（1）--Docker原理及安装
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一：Docker简介
（1）概念
Docker 是一个开源的应用容器引擎，让开发者可以打包他们的应用以及依赖包到一个可移植的镜像中，然后发布到任何流行的
Linux或Windows 机器上，也可以实现虚拟化。容器是完全使用沙箱机制，相互之间不会有任何接口。非常方便。
（2）架构
一个完整的Docker有以下几个部分组成：
- DockerClient客户端
- Docker Daemon守护进程
- Docker Image镜像
- DockerContainer容器
Docker daemon 一般在宿主主机后台运行，等待接收来自客户端的消息。 Docker
客户端则为用户提供一系列可执行命令，用户用这些命令实现跟 Docker daemon 交互
（3）特性
- Automating the packaging and deployment of
applications（使应用的打包与部署自动化） - Creation of lightweight, private PAAS environments（创建轻量、私密的PAAS环境）
- Automated testing and continuous
integration/deployment（实现自动化测试和持续的集成/部署） - Deploying and scaling web apps, databases and backend
services（部署与扩展webapp、数据库和后台服务）
由于其基于LXC的轻量级虚拟化的特点，docker相比KVM之类最明显的特点就是启动快，资源占用小。因此对于构建隔离的标准化的运行环境，轻量级的PaaS(如dokku),
构建自动化测试和持续集成环境，以及一切可以横向扩展的应用(尤其是需要快速启停来应对峰谷的web应用)。
（4）局限
Docker是基于Linux 64bit的，无法在32bit的linux/Windows/unix环境下使用
LXC是基于cgroup等linux kernel功能的，因此container的guest系统只能是linux base的
隔离性相比KVM之类的虚拟化方案还是有些欠缺，所有container公用一部分的运行库 网络管理相对简单，主要是基于namespace隔离
cgroup的cpu和cpuset提供的cpu功能相比KVM的等虚拟化方案相比难以度量(所以dotcloud主要是按内存收费)
Docker对disk的管理比较有限 container随着用户进程的停止而销毁，container中的log等用户数据不便收集
（5）Docker和Vm区别
1.实现原理不同
VM通过Hypervisor提供基础环境实现虚拟机 Docker通过docker
engine与物理机共享操作系统而不是在向虚拟机一样，完全仿真一个虚拟操作系统，Docker达到了类似虚拟机的效果，但是又没有虚拟机的开销，它虚拟的层次更加高。Docker不虚拟机器，仅仅虚拟应用的运行环境
2.使用上的区别
Docker在宿主机器的操作系统上创建Docker引擎，直接在宿主主机的操作系统上调用硬件资源，而不是虚拟化操作系统和硬件资源，所以操作速度快。
这个其实安装一个ubuntu的虚拟机和拉取一个Docker的ubuntu镜像文件，运行一下就知道了，区别很明显，虚拟机开一下大概得2分多钟，而Docker只需要2秒钟。
二：docker三个特征
镜像
容器
仓库
docker实际可以理解为简易版的linux系统
容器就是镜像的一个实例
仓库（Repository）是存放镜像的厂所
仓库注册服务器（Registry）放着多个仓库，每个仓库又放着多个镜像，每个镜像又有不同的标签（类似版本号）
仓库分为公开仓库和私有仓库两种形式 最大的公开库是Docker Hub。（太慢，国外网站） 国内公开仓库包括阿里云，网易云
三、docker的安装及测试
部署环境：
[root@a ~]# ping qq.com
PING qq.com (125.39.52.26) 56(84) bytes of data.
64 bytes from no-data (125.39.52.26): icmp_seq=1 ttl=50 time=59.6 ms
64 bytes from no-data (125.39.52.26): icmp_seq=2 ttl=50 time=152 ms
64 bytes from no-data (125.39.52.26): icmp_seq=3 ttl=50 time=210 ms
64 bytes from no-data (125.39.52.26): icmp_seq=4 ttl=50 time=88.2 ms
^C
--- qq.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3015ms
rtt min/avg/max/mdev = 59.646/127.784/210.411/58.431 ms
[root@a ~]# cat /etc/redhat-release
CentOS Linux release 7.7.1908 (Core)
[root@a ~]# uname -r
3.10.0-1062.el7.x86_64
1、设置yum源
[root@a ~]# yum install -y yum-utils
[root@a ~]# yum-config-manager \
--add-repo \
https://download.docker.com/linux/centos/docker-ce.repo
[root@a ~]# yum makecache fast
Docker安装报错：containerd.io-1.2.13-3.1.el7.x86_64 (docker-ce-stable) 需要：container-selinux >= 2:2.74
解决方案：
[root@a ~]# yum install -y wget
[root@a ~]# wget -O http://mirrors.aliyun.com/repo/Centos-7.repo
[root@a ~]# mv Centos-7.repo /etc/yum.repos.d/
[root@a ~]# yum install epel-release
[root@a ~]# yum install container-selinux
2、安装最新版本的 Docker Engine-Community 和 containerd
[root@a ~]# yum install docker-ce docker-ce-cli containerd.io
...
Installed:
containerd.io.x86_64 0:1.2.13-3.2.el7 docker-ce.x86_64 3:19.03.8-3.el7
docker-ce-cli.x86_64 1:19.03.8-3.el7
Complete!
3、启动服务
[root@a ~]# systemctl start docker
[root@a ~]# docker --version
Docker version 19.03.8, build afacb8b
4、配置镜像加速器
登录阿里云搜素镜像加速器
[root@a ~]# mkdir -p /etc/docker
[root@a ~]# tee /etc/docker/daemon.json <<-'EOF'
{
"registry-mirrors": ["https://..............."]
}
EOF
[root@a ~]# systemctl daemon-reload
[root@a ~]# systemctl restart docker
[root@a ~]# ps -ef |grep docker
root 12225 1 0 08:10 ? 00:00:00 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
root 12362 1737 0 08:12 pts/0 00:00:00 grep --color=auto docker
5、测试
[root@a ~]# docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
0e03bdcc26d7: Pull complete
Digest: sha256:6a65f928fb91fcfbc963f7aa6d57c8eeb426ad9a20c7ee045538ef34847f44f1
Status: Downloaded newer image for hello-world:latest
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
Share images, automate workflows, and more with a free Docker ID:
https://hub.docker.com/
For more examples and ideas, visit:
https://docs.docker.com/get-started/
6、run有什么用？
开始>>>docker在本机中寻找镜像>>>本机是否有该镜像{1.有，以镜像为模板生产容器实例运行 2.没有，去dockerHub上找}>>>dockerHub上能否找到{1.能，下载镜像到本地，以镜像为模板生产容器实例运行 2.不能，返回错误值结束}
7、基础命令
一、帮助命令
1、docker version（查看docker基本信息）
[root@a ~]# docker version
Client: Docker Engine - Community
Version: 19.03.8
API version: 1.40
Go version: go1.12.17
Git commit: afacb8b
Built: Wed Mar 11 01:27:04 2020
OS/Arch: linux/amd64
Experimental: false
Server: Docker Engine - Community
Engine:
Version: 19.03.8
API version: 1.40 (minimum version 1.12)
Go version: go1.12.17
Git commit: afacb8b
Built: Wed Mar 11 01:25:42 2020
OS/Arch: linux/amd64
Experimental: false
containerd:
Version: 1.2.13
GitCommit: 7ad184331fa3e55e52b890ea95e65ba581ae3429
runc:
Version: 1.0.0-rc10
GitCommit: dc9208a3303feef5b3839f4323d9beb36df0a9dd
docker-init:
Version: 0.18.0
GitCommit: fec3683
二、docker info(查看容器信息)
[root@a ~]# docker info
Client:
Debug Mode: false
Server:
Containers: 1
Running: 0
Paused: 0
Stopped: 1
Images: 1
Server Version: 19.03.8
Storage Driver: overlay2
Backing Filesystem: <unknown>
Supports d_type: true
Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 7ad184331fa3e55e52b890ea95e65ba581ae3429
runc version: dc9208a3303feef5b3839f4323d9beb36df0a9dd
init version: fec3683
Security Options:
seccomp
Profile: default
Kernel Version: 3.10.0-1062.el7.x86_64
Operating System: CentOS Linux 7 (Core)
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 972.4MiB
Name: a
ID: VIBZ:LAXM:EH6G:R2JL:MQYU:7D25:HCZT:V234:BEP5:ZV67:RPG7:LZFY
Docker Root Dir: /var/lib/docker
Debug Mode: false
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
127.0.0.0/8
Registry Mirrors:
https://wuz1gh9p.mirror.aliyuncs.com/
Live Restore Enabled: false
三、docker --help
[root@a ~]# docker --help
Usage: docker [OPTIONS] COMMAND
A self-sufficient runtime for containers
Options:
--config string Location of client config files (default "/root/.docker")
-c, --context string Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var
and default context set with "docker context use")
-D, --debug Enable debug mode
-H, --host list Daemon socket(s) to connect to
-l, --log-level string Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
--tls Use TLS; implied by --tlsverify
--tlscacert string Trust certs signed only by this CA (default "/root/.docker/ca.pem")
--tlscert string Path to TLS certificate file (default "/root/.docker/cert.pem")
--tlskey string Path to TLS key file (default "/root/.docker/key.pem")
--tlsverify Use TLS and verify the remote
-v, --version Print version information and quit
Management Commands:
builder Manage builds
config Manage Docker configs
container Manage containers
context Manage contexts
engine Manage the docker engine
image Manage images
network Manage networks
node Manage Swarm nodes
plugin Manage plugins
secret Manage Docker secrets
service Manage services
stack Manage Docker stacks
swarm Manage Swarm
system Manage Docker
trust Manage trust on Docker images
volume Manage volumes
Commands:
attach Attach local standard input, output, and error streams to a running container
build Build an image from a Dockerfile
commit Create a new image from a container's changes
cp Copy files/folders between a container and the local filesystem
create Create a new container
diff Inspect changes to files or directories on a container's filesystem
events Get real time events from the server
exec Run a command in a running container
export Export a container's filesystem as a tar archive
history Show the history of an image
images List images
import Import the contents from a tarball to create a filesystem image
info Display system-wide information
inspect Return low-level information on Docker objects
kill Kill one or more running containers
load Load an image from a tar archive or STDIN
login Log in to a Docker registry
logout Log out from a Docker registry
logs Fetch the logs of a container
pause Pause all processes within one or more containers
port List port mappings or a specific mapping for the container
ps List containers
pull Pull an image or a repository from a registry
push Push an image or a repository to a registry
rename Rename a container
restart Restart one or more containers
rm Remove one or more containers
rmi Remove one or more images
run Run a command in a new container
save Save one or more images to a tar archive (streamed to STDOUT by default)
search Search the Docker Hub for images
start Start one or more stopped containers
stats Display a live stream of container(s) resource usage statistics
stop Stop one or more running containers
tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
top Display the running processes of a container
unpause Unpause all processes within one or more containers
update Update configuration of one or more containers
version Show the Docker version information
wait Block until one or more containers stop, then print their exit
