Hello Docker入门实例
本文共 16322 字，大约阅读时间需要 54 分钟。
1. 什么是docker
一个分布式应用的开放平台，相比VM更加轻量级，可以不经任何更改运行在任意平台，任意终端
2 与VM的比较
3. Docker 构成组件
- Docker image: 一个只读的template 文件，很多base的template可以从hub获取。一个image可以包含一个基本的ubuntu 操作系统和你的web appliation
- Docker registry ： 管理template文件的仓库，可以pull（获取），修改后，push template文件进行update
- Docker container： 从template launch的运行容器，类似于目录，包含application运行需要的一切东西，可以被启动，停止，运行，删除，移动等操作
4. Docker 安装
在CentOS 7 上安装Docker，如下所示：
[plcm@ngmadev ~]$ sudo yum install docker[sudo] password for plcm: Loaded plugins: fastestmirrorWandiscoSVN-CentOS6 | 951 B 00:00 base | 3.6 kB 00:00 extras | 3.4 kB 00:00 google-chrome | 951 B 00:00 updates | 3.4 kB 00:00 zulu | 2.9 kB 00:00 Loading mirror speeds from cached hostfile * base: mirrors.neusoft.edu.cn * epel: mirrors.vinahost.vn * extras: mirrors.neusoft.edu.cn * updates: mirror.neu.edu.cnResolving Dependencies--> Running transaction check---> Package docker.x86_64 0:1.3.2-4.el7.centos will be installed--> Processing Dependency: systemd-units >= 208-11.el7_0.5 for package: docker-1.3.2-4.el7.centos.x86_64--> Running transaction check---> Package systemd.x86_64 0:208-11.el7_0.2 will be updated--> Processing Dependency: systemd = 208-11.el7_0.2 for package: systemd-python-208-11.el7_0.2.x86_64--> Processing Dependency: systemd = 208-11.el7_0.2 for package: systemd-sysv-208-11.el7_0.2.x86_64--> Processing Dependency: systemd = 208-11.el7_0.2 for package: libgudev1-208-11.el7_0.2.x86_64---> Package systemd.x86_64 0:208-11.el7_0.6 will be an update--> Processing Dependency: systemd-libs = 208-11.el7_0.6 for package: systemd-208-11.el7_0.6.x86_64--> Running transaction check---> Package libgudev1.x86_64 0:208-11.el7_0.2 will be updated---> Package libgudev1.x86_64 0:208-11.el7_0.6 will be an update---> Package systemd-libs.x86_64 0:208-11.el7_0.2 will be updated---> Package systemd-libs.x86_64 0:208-11.el7_0.6 will be an update---> Package systemd-python.x86_64 0:208-11.el7_0.2 will be updated---> Package systemd-python.x86_64 0:208-11.el7_0.6 will be an update---> Package systemd-sysv.x86_64 0:208-11.el7_0.2 will be updated---> Package systemd-sysv.x86_64 0:208-11.el7_0.6 will be an update--> Finished Dependency ResolutionDependencies Resolved================================================================================ Package Arch Version Repository Size================================================================================Installing: docker x86_64 1.3.2-4.el7.centos extras 5.6 MUpdating for dependencies: libgudev1 x86_64 208-11.el7_0.6 updates 48 k systemd x86_64 208-11.el7_0.6 updates 2.6 M systemd-libs x86_64 208-11.el7_0.6 updates 154 k systemd-python x86_64 208-11.el7_0.6 updates 83 k systemd-sysv x86_64 208-11.el7_0.6 updates 36 kTransaction Summary================================================================================Install 1 PackageUpgrade ( 5 Dependent packages)Total size: 8.5 MTotal download size: 5.6 MIs this ok [y/d/N]: yDownloading packages:docker-1.3.2-4.el7.centos.x86_64.rpm 55% [======================- ] 39 kB/s | 3.1 MB 00:01:06 ETA docker-1.3.2-4.el7.centos.x86_64.rpm 55% [======================-docker-1.3.2-4.el7.centos.x86_64.rpm | 5.6 MB 00:02:31 Running transaction checkRunning transaction testTransaction test succeededRunning transaction Updating : systemd-libs-208-11.el7_0.6.x86_64 1/11 Updating : systemd-208-11.el7_0.6.x86_64 2/11 Updating : systemd-sysv-208-11.el7_0.6.x86_64 3/11 Updating : systemd-python-208-11.el7_0.6.x86_64 4/11 Installing : docker-1.3.2-4.el7.centos.x86_64 5/11 Updating : libgudev1-208-11.el7_0.6.x86_64 6/11 Cleanup : systemd-sysv-208-11.el7_0.2.x86_64 7/11 Cleanup : libgudev1-208-11.el7_0.2.x86_64 8/11 Cleanup : systemd-python-208-11.el7_0.2.x86_64 9/11 Cleanup : systemd-208-11.el7_0.2.x86_64 10/11 Cleanup : systemd-libs-208-11.el7_0.2.x86_64 11/11 Verifying : systemd-sysv-208-11.el7_0.6.x86_64 1/11 Verifying : systemd-python-208-11.el7_0.6.x86_64 2/11 Verifying : docker-1.3.2-4.el7.centos.x86_64 3/11 Verifying : libgudev1-208-11.el7_0.6.x86_64 4/11 Verifying : systemd-libs-208-11.el7_0.6.x86_64 5/11 Verifying : systemd-208-11.el7_0.6.x86_64 6/11 Verifying : systemd-208-11.el7_0.2.x86_64 7/11 Verifying : systemd-sysv-208-11.el7_0.2.x86_64 8/11 Verifying : systemd-python-208-11.el7_0.2.x86_64 9/11 Verifying : libgudev1-208-11.el7_0.2.x86_64 10/11 Verifying : systemd-libs-208-11.el7_0.2.x86_64 11/11 Installed: docker.x86_64 0:1.3.2-4.el7.centos Dependency Updated: libgudev1.x86_64 0:208-11.el7_0.6 systemd.x86_64 0:208-11.el7_0.6 systemd-libs.x86_64 0:208-11.el7_0.6 systemd-python.x86_64 0:208-11.el7_0.6 systemd-sysv.x86_64 0:208-11.el7_0.6 Complete![plcm@ngmadev ~]$ cat /etc/redhat-release CentOS Linux release 7.0.1406 (Core)
启动 docker daemon
[plcm@ngmadev ~]$ sudo service docker start[sudo] password for plcm: Redirecting to /bin/systemctl start docker.service[plcm@ngmadev ~]$ ps -ef |grep dockerroot 20011 1 2 00:28 ? 00:00:00 /usr/bin/docker -d --selinux-enabled -H fd://plcm 20108 19566 0 00:28 pts/1 00:00:00 grep --color=auto docker为了测试docker运行正常，我们download一个最新的centos image 试试，如下命令：
[plcm@ngmadev ~]$ sudo docker pull centosPulling repository centos8efe422e6104: Pulling image (latest) from centos, endpoint: https://registry-1.d8efe422e6104: Download complete 511136ea3c5a: Download complete 5b12ef8fd570: Download complete Status: Downloaded newer image for centos:latest
[plcm@ngmadev ~]$ sudo docker images centosREPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZEcentos centos7 8efe422e6104 13 days ago 224 MBcentos latest 8efe422e6104 13 days ago 224 MBcentos 7 8efe422e6104 13 days ago
运行bash shell 验证是否work，执行成功后，我们进入了一个交互性的container：[plcm@ngmadev ~]$ sudo docker run -i -t centos /bin/bash[root@b71bd0592d60 /]#
[root@33303b62503b /]# echo "hello docker" hello docker[root@b71bd0592d60 /]# dfFilesystem 1K-blocks Used Available Use% Mounted on/dev/mapper/docker-253:1-522936-b71bd0592d6006b4592c63d0ecded912b83135e9833e75fc656ac475ab06bb37 10190100 265636 9383792 3% /tmpfs 1941740 0 1941740 0% /devshm 65536 0 65536 0% /dev/shm/dev/mapper/centos-root 17938820 9497724 7506800 56% /etc/hoststmpfs 1941740 0 1941740 0% /run/secretstmpfs 1941740 0 1941740 0% /proc/kcore
一旦我们输入exit后者ctrl+z终止后，container也将停止。如下图，我们通过docker ps 命令查询运行的container，一旦exit退出后，container也会停止运行
[plcm@ngmadev ~]$ sudo docker psCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES33303b62503b centos:7 "/bin/bash" 5 minutes ago Up 5 minutes angry_elion
运行exit命令后，container停止运行，结果为空
[plcm@ngmadev ~]$ sudo docker psCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES5. 在container上运行一个复杂点的web 应用
[plcm@ngmadev ~]$ sudo docker run -d -P training/webapp python app.pyUnable to find image 'training/webapp' locallyPulling repository training/webapp31fa814ba25a: Pulling image (latest) from training/webapp, endpoint: https://reg31fa814ba25a: Pulling dependent layers 511136ea3c5a: Download complete f10ebce2c0e1: Downloading [======================> ] 17.3 MB/39.17 MB 1m39s这个web应用为docker官方提供，本地没有，所以自动去仓库下载，很方便的实现image，code 共享，并且到处运行。
image都是分层的，所以更改后构建比较快速。
此web 应用成功运行，访问页面如下：http://10.220.209.10:49153/
查看运行的container：
[plcm@ngmadev ~]$ sudo docker psCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMESdac947a0be14 training/webapp:latest "python app.py" 4 minutes ago Up 4 minutes 0.0.0.0:49153->5000/tcp kickass_pasteur
[plcm@ngmadev ~]$ sudo docker inspect kickass_pasteur[{ "AppArmorProfile": "", "Args": [ "app.py" ], "Config": { "AttachStderr": false, "AttachStdin": false, "AttachStdout": false, "Cmd": [ "python", "app.py" ], "CpuShares": 0, "Cpuset": "", "Domainname": "", "Entrypoint": null, "Env": [ "HOME=/", "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" ], "ExposedPorts": { "5000/tcp": {} }, "Hostname": "dac947a0be14", "Image": "training/webapp", "Memory": 0, "MemorySwap": 0, "NetworkDisabled": false, "OnBuild": null, "OpenStdin": false, "PortSpecs": null, "StdinOnce": false, "Tty": false, "User": "", "Volumes": null, "WorkingDir": "/opt/webapp" }, "Created": "2015-01-19T06:13:47.740587544Z", "Driver": "devicemapper", "ExecDriver": "native-0.2", "HostConfig": { "Binds": null, "CapAdd": null, "CapDrop": null, "ContainerIDFile": "", "Devices": [], "Dns": null, "DnsSearch": null, "ExtraHosts": null, "Links": null, "LxcConf": [], "NetworkMode": "bridge", "PortBindings": {}, "Privileged": false, "PublishAllPorts": true, "RestartPolicy": { "MaximumRetryCount": 0, "Name": "" }, "SecurityOpt": null, "VolumesFrom": null }, "HostnamePath": "/var/lib/docker/containers/dac947a0be14ff0c1fceb1a5af7c6b82af6f6b5599bdc13ce4f9f7ead5d8665d/hostname", "HostsPath": "/var/lib/docker/containers/dac947a0be14ff0c1fceb1a5af7c6b82af6f6b5599bdc13ce4f9f7ead5d8665d/hosts", "Id": "dac947a0be14ff0c1fceb1a5af7c6b82af6f6b5599bdc13ce4f9f7ead5d8665d", "Image": "31fa814ba25ae3426f8710df7a48d567d4022527ef2c14964bb8bc45e653417c", "MountLabel": "", "Name": "/kickass_pasteur", "NetworkSettings": { "Bridge": "docker0", "Gateway": "172.17.42.1", "IPAddress": "172.17.0.5", "IPPrefixLen": 16, "MacAddress": "02:42:ac:11:00:05", "PortMapping": null, "Ports": { "5000/tcp": [ { "HostIp": "0.0.0.0", "HostPort": "49153" } ] } }, "Path": "python", "ProcessLabel": "", "ResolvConfPath": "/var/lib/docker/containers/dac947a0be14ff0c1fceb1a5af7c6b82af6f6b5599bdc13ce4f9f7ead5d8665d/resolv.conf", "State": { "ExitCode": 0, "FinishedAt": "0001-01-01T00:00:00Z", "Paused": false, "Pid": 21678, "Restarting": false, "Running": true, "StartedAt": "2015-01-19T06:13:48.540050644Z" }, "Volumes": {}, "VolumesRW": {}}$ sudo docker start nostalgic_morsenostalgic_morse
6. 如何自定义image
以上我们都是利用hub上已经存在的image进行操作，如何自定义image呢？继续研究。
查询localhost拥有的image，先前建立起来的image：
[plcm@ngmadev ~]$ sudo docker imagesREPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZEcentos 7 8efe422e6104 13 days ago 224 MBcentos centos7 8efe422e6104 13 days ago 224 MBcentos latest 8efe422e6104 13 days ago 224 MBtraining/webapp latest 31fa814ba25a 7 months ago 278.6 MB第一种方法，从image创建container后，更新container，commit结果到image
第二种方法是利用dockerfile指定指令创建image
先测试第一个方法：
修改我们之前的centos image，增加一个文件，名字为kerry.log文件
[root@91f2108f31ee /]# touch kerry.log[root@91f2108f31ee /]# lsbin etc kerry.log lib64 media opt root sbin srv tmp vardev home lib lost+found mnt proc run selinux sys usrcommit改变到image，此时仍未local image
[plcm@ngmadev ~]$ sudo docker commit -m="add log file" -a="kerry" 91f2108f31ee kerry/centos:v2ef5dbe35d8460043f360a392c32e4fb2e8b8bccfe223241bc47401035c02ff15
[plcm@ngmadev ~]$ sudo docker imagesREPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZEkerry/centos v2 ef5dbe35d846 54 seconds ago 224 MBcentos 7 8efe422e6104 13 days ago 224 MBcentos centos7 8efe422e6104 13 days ago 224 MBcentos latest 8efe422e6104 13 days ago 224 MBtraining/webapp latest 31fa814ba25a 7 months ago 278.6 MB利用 sudo docker push 更新image到hub
[plcm@ngmadev ~]$ sudo docker push kerry/centosThe push refers to a repository [kerry/centos] (len: 1)Sending image listPlease login prior to push:Username: kerryPassword: Email: kerry@gmail.comAccount created. Please use the confirmation link we sent to your e-mail to activate it.The push refers to a repository [kerry/centos] (len: 1)Sending image list2015/01/19 01:45:40 Error: Status 403 trying to push repository kerry/centos: Account is not Active
7 Container之间可以建立link skip， 详见：https://docs.docker.com/userguide/dockerlinks/
8 管理container的数据，skip
详见： https://docs.docker.com/userguide/dockervolumes/
9. docker注册账户，上传，下载image等常用命令
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