Docker入门学习（一）
1.什么是Docker？
Docker 是一个开源的应用容器引擎，基于 Go 语言 并遵从 Apache2.0 协议开源。
Docker 可以让开发者打包他们的应用以及依赖包到一个轻量级、可移植的容器中，然后发布到任何流行的 Linux 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（类似 iPhone 的 app）,更重要的是容器性能开销极低。
2.Docker的应用场景
Web 应用的自动化打包和发布。
自动化测试和持续集成、发布。
在服务型环境中部署和调整数据库或其他的后台应用。
从头编译或者扩展现有的 OpenShift 或 Cloud Foundry 平台来搭建自己的 PaaS 环境。
3.Docker 的优点
快速，一致地交付您的应用程序
响应式部署和扩展
在同一硬件上运行更多工作负载
总之一句话就是一次构建，到处运行。
4.Docker的架构
镜像（Image）：Docker 镜像，就相当于是一个 root 文件系统。比如官方镜像 ubuntu:16.04 就包含了完整的一套 Ubuntu16.04 最小系统的 root 文件系统。
容器（Container）：镜像和容器的关系，就像是面向对象程序设计中的类和实例一样，镜像是静态的定义，容器是镜像运行时的实体。容器可以被创建、启动、停止、删除、暂停等。可以把容器看做是一个简易版的Linux环境。
仓库（Repository）：仓库可看着一个代码控制中心，用来保存镜像。
我们可以拿Java做一个类比
| Docker | Java |
| 镜像 | 类 |
| 容器 | 对象 |
比如：
Person p1 = new Person()； Person p2 = new Person()； Person p3 = new Person()；
Person就是镜像，p1、p2、p3就是容器。
以下是Docker的架构图：
5.Docker的安装
Docker的安装教程网上有很多，在这里就不在赘述。
6.Docker容器与虚拟机的区别
7.Docker帮助命令
（1）查看docker的信息：docker version
Client: Version: 1.13.1 API version: 1.26 Package version: docker-1.13.1-109.gitcccb291.el7.centos.x86_64 Go version: go1.10.3 Git commit: cccb291/1.13.1 Built: Tue Mar 3 17:21:24 2020 OS/Arch: linux/amd64 Server: Version: 1.13.1 API version: 1.26 (minimum version 1.12) Package version: docker-1.13.1-109.gitcccb291.el7.centos.x86_64 Go version: go1.10.3 Git commit: cccb291/1.13.1 Built: Tue Mar 3 17:21:24 2020 OS/Arch: linux/amd64 Experimental: false
（2）查看Docker的更详细信息：docker info
Containers: 3 Running: 3 Paused: 0 Stopped: 0 Images: 3 Server Version: 1.13.1 Storage Driver: overlay2 Backing Filesystem: extfs Supports d_type: true Native Overlay Diff: false Logging Driver: journald Cgroup Driver: systemd Plugins: Volume: local Network: bridge host macvlan null overlay Swarm: inactive Runtimes: docker-runc runc Default Runtime: docker-runc Init Binary: /usr/libexec/docker/docker-init-current containerd version: (expected: aa8187dbd3b7ad67d8e5e3a15115d3eef43a7ed1) runc version: 66aedde759f33c190954815fb765eedc1d782dd9 (expected: 9df8b306d01f59d3a8029be411de015b7304dd8f) init version: fec3683b971d9c3ef73f284f176672c44b448662 (expected: 949e6facb77383876aeff8a6944dde66b3089574) Security Options: seccomp WARNING: You're not using the default seccomp profile Profile: /etc/docker/seccomp.json Kernel Version: 3.10.0-514.26.2.el7.x86_64 Operating System: CentOS Linux 7 (Core) OSType: linux Architecture: x86_64 Number of Docker Hooks: 3 CPUs: 1 Total Memory: 1.796 GiB Name: iZbp1j71l9e8k40vg0cb02Z ID: QQUC:WWSZ:FOER:ZUNE:OTEP:3EVT:IENO:CDME:JRV7:U7AK:YS5J:S7R7 Docker Root Dir: /var/lib/docker Debug Mode (client): false Debug Mode (server): false Registry: https://index.docker.io/v1/ WARNING: bridge-nf-call-iptables is disabled WARNING: bridge-nf-call-ip6tables is disabled Experimental: false Insecure Registries: 127.0.0.0/8 Registry Mirrors: https://3huzqv5x.mirror.aliyuncs.com Live Restore Enabled: false Registries: docker.io (secure)
（3）查看docker的命令：docker help
Usage: docker COMMAND A self-sufficient runtime for containers Options: --config string Location of client config files (default "/root/.docker") -D, --debug Enable debug mode --help Print usage -H, --host list Daemon socket(s) to connect to (default []) -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: container Manage containers 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 volume Manage volumes Commands: attach Attach 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 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 codes
8.Docker镜像命令
（1）查看本地的docker镜像：docker images
字段说明：
可以使用REPOSITORY：TAG来定义不同的镜像
其他可选命令：
列出全部镜像（包含中间镜像）：docker images -a
只显示镜像ID ：docker images -q
显示镜像说明：docker images --digests
（2）搜索某个镜像：docker search “xxx”
它是从https://hub.docker.com/去查找xxx镜像，但是拉取的时候是从配置的阿里云镜像加速器来pull的。
[root@iZbp1j71l9e8k40vg0cb02Z ~]# docker search tomcat INDEX NAME DESCRIPTION STARS OFFICIAL AUTOMATED docker.io docker.io/tomcat Apache Tomcat is an open source implementa... 2737 [OK] docker.io docker.io/tomee Apache TomEE is an all-Apache Java EE cert... 79 [OK] docker.io docker.io/dordoka/tomcat Ubuntu 14.04, Oracle JDK 8 and Tomcat 8 ba... 54 [OK] docker.io docker.io/bitnami/tomcat Bitnami Tomcat Docker Image 33 [OK] docker.io docker.io/kubeguide/tomcat-app Tomcat image for Chapter 1 28 docker.io docker.io/consol/tomcat-7.0 Tomcat 7.0.57, 8080, "admin/admin" 17 [OK] docker.io docker.io/cloudesire/tomcat Tomcat server, 6/7/8 15 [OK] docker.io docker.io/aallam/tomcat-mysql Debian, Oracle JDK, Tomcat & MySQL 12 [OK] docker.io docker.io/arm32v7/tomcat Apache Tomcat is an open source implementa... 10 docker.io docker.io/rightctrl/tomcat CentOS , Oracle Java, tomcat application s... 6 [OK] docker.io docker.io/maluuba/tomcat7-java8 Tomcat7 with java8. 5 docker.io docker.io/unidata/tomcat-docker Security-hardened Tomcat Docker container. 4 [OK] docker.io docker.io/amd64/tomcat Apache Tomcat is an open source implementa... 2 docker.io docker.io/arm64v8/tomcat Apache Tomcat is an open source implementa... 2 docker.io docker.io/jelastic/tomcat An image of the Tomcat Java application se... 2 docker.io docker.io/99taxis/tomcat7 Tomcat7 1 [OK] docker.io docker.io/camptocamp/tomcat-logback Docker image for tomcat with logback integ... 1 [OK] docker.io docker.io/i386/tomcat Apache Tomcat is an open source implementa... 1 docker.io docker.io/oobsri/tomcat8 Testing CI Jobs with different names. 1 docker.io docker.io/ppc64le/tomcat Apache Tomcat is an open source implementa... 1 docker.io docker.io/appsvc/tomcat 0 docker.io docker.io/cfje/tomcat-resource Tomcat Concourse Resource 0 docker.io docker.io/picoded/tomcat7 tomcat7 with jre8 and MANAGER_USER / MANAG... 0 [OK] docker.io docker.io/s390x/tomcat Apache Tomcat is an open source implementa... 0 docker.io docker.io/secoresearch/tomcat-varnish Tomcat and Varnish 5.0 0 [OK]
只显示STARS多于30的镜像 docker search -s n xxx
[root@iZbp1j71l9e8k40vg0cb02Z ~]# docker search -s 30 tomcat Flag --stars has been deprecated, use --filter=stars=3 instead INDEX NAME DESCRIPTION STARS OFFICIAL AUTOMATED docker.io docker.io/tomcat Apache Tomcat is an open source implementa... 2737 [OK] docker.io docker.io/tomee Apache TomEE is an all-Apache Java EE cert... 79 [OK] docker.io docker.io/dordoka/tomcat Ubuntu 14.04, Oracle JDK 8 and Tomcat 8 ba... 54 [OK] docker.io docker.io/bitnami/tomcat Bitnami Tomcat Docker Image 33 [OK]
（3）拉取某个镜像：docker pull xxx
比如要拉取tomcat下来，可以docker pull tomcat，它是等价于docker pull tomcat:latest的，所以如果想要拉取不同的版本，那就可以用在镜像名后面多添加一个版本号。
[root@iZbp1j71l9e8k40vg0cb02Z ~]# docker pull tomcat Using default tag: latest Trying to pull repository docker.io/library/tomcat ... latest: Pulling from docker.io/library/tomcat 376057ac6fa1: Pull complete 5a63a0a859d8: Pull complete 496548a8c952: Pull complete 2adae3950d4d: Pull complete 0a297eafb9ac: Pull complete 09a4142c5c9d: Pull complete 9e78d9befa39: Pull complete 18f492f90b9c: Pull complete 7834493ec6cd: Pull complete 216b2be21722: Pull complete Digest: sha256:ce753be7b61d86f877fe5065eb20c23491f783f283f25f6914ba769fee57886b Status: Downloaded newer image for docker.io/tomcat:latest
再用docker images来查看一下本地的镜像
[root@iZbp1j71l9e8k40vg0cb02Z ~]# docker images REPOSITORY TAG IMAGE ID CREATED SIZE docker.io/tomcat latest 1b6b1fe7261e 9 days ago 647 MB docker.io/mongo latest 3f3daf863757 4 weeks ago 388 MB docker.io/redis latest 4cdbec704e47 7 weeks ago 98.2 MB docker.io/mysql 5.7 413be204e9c3 8 weeks ago 456 MB
我们发现，tomcat已经被拉取到本地了，它的大小是647 MB，这是有点奇怪的，这是为什么？后面再解释！
（4）删除掉某个镜像 docker rmi -f 镜像id
删除多个镜像 docker rmi -f 镜像名1:TAG 镜像名2:TAG ......
删除全部镜像，这是一个组合命令 docker rmi -f $(docker images -qa)
