构建镜像

（对Docker感兴趣的朋友可以加我的微信ghostcloud2016，然后我把你加到我们的一个Docker爱好者群组里面。）

镜像(Image)是容器的基础。当你运行docker run的时候，你会指定一个Image来运行。比如，最基本的ubuntu镜像和training/webapp镜像。 在上一节中，我们是从Docker Hub下载的ubuntu镜像。在本节中，我们将做如下操作：

• 管理和运行你的本地镜像
• 创建基础镜像

1 查看本机的镜像

root@gctest:~/.ghostcloud/proxy/conf# docker images REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE ghostcloud.cn:5005/gcali 1.0.7 553ff90cea5d 40 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.6 0704f2860bd6 41 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.3 746ac51185f2 42 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.2 b06108e12275 43 hours ago 219.6 MB ubuntu latest e9ae3c220b23 3 weeks ago 187.9 MB 

上面你可以看到你本机的docker镜像，其中ubuntu是一个基础镜像，来自于docker hub，而ghostcloud.cn:5005/gcali是来自于ghostcloud.cn的第三方镜像。我们可以看到有几个镜像都是ghostcloud.cn:5005/gcali，但他们拥有不同的TAG，类似于版本。接下来，我们可以通过docker run来运行镜像。

root@gctest:~/.ghostcloud/proxy/conf# docker run -i -t ubuntu:latest /bin/bash root@46ffa55f5680:/# 

2 获取新的image

我们如何来获取新镜像呢？其实之前我们的docker run包含了镜像的拉取，我们可以通过docker pull拉取镜像，并且不启动镜像。

$ docker pull centos Pulling repository centos b7de3133ff98: Pulling dependent layers 5cc9e91966f7: Pulling fs layer 511136ea3c5a: Download complete ef52fb1fe610: Download complete . . . Status: Downloaded newer image for centos 

之后，我们可以运行这个镜像：

$ docker run -t -i centos /bin/bash bash-4.1# 

3 查找Image

我们可以通过docker search命令来搜索镜像，假入我们要搜索mysql:

root@46ffa55f5680:/# exitroot@gctest:~/.ghostcloud/proxy/conf# docker search ubuntu NAME DESCRIPTION STARS OFFICIAL AUTOMATED ubuntu Ubuntu is a Debian-based Linux operating s... 2778 [OK] ubuntu-upstart Upstart is an event-based replacement for ... 48 [OK] dorowu/ubuntu-desktop-lxde-vnc Ubuntu with openssh-server and NoVNC on po... 28 [OK] sequenceiq/hadoop-ubuntu An easy way to try Hadoop on Ubuntu 25 [OK] torusware/speedus-ubuntu Always updated official Ubuntu docker imag... 25 [OK] ubuntu-debootstrap debootstrap --variant=minbase --components... 20 [OK] tleyden5iwx/ubuntu-cuda Ubuntu 14.04 with CUDA drivers pre-installed 18 [OK] rastasheep/ubuntu-sshd Dockerized SSH service, built on top of of... 15 [OK] consol/ubuntu-xfce-vnc Ubuntu container with "headless" VNC sessi... 7 [OK] n3ziniuka5/ubuntu-oracle-jdk Ubuntu with Oracle JDK. Check tags for ver... 5 [OK] nuagebec/ubuntu Simple always updated Ubuntu docker images... 4 [OK] ioft/armhf-ubuntu [ABR] Ubuntu Docker images for the ARMv7(a... 4 [OK] nimmis/ubuntu This is a docker images different LTS vers... 3 [OK] maxexcloo/ubuntu Docker base image built on Ubuntu with Sup... 2 [OK] densuke/ubuntu-jp-remix Ubuntu Linuxの日本語remix風味です 1 [OK] seetheprogress/ubuntu Ubuntu image provided by seetheprogress us... 1 [OK] sylvainlasnier/ubuntu Ubuntu 15.04 root docker images with commo... 1 [OK] tvaughan/ubuntu https://github.com/tvaughan/docker-ubuntu 0 [OK] rallias/ubuntu Ubuntu with the needful 0 [OK] zoni/ubuntu 0 [OK] partlab/ubuntu Simple Ubuntu docker images. 0 [OK] vicamo/ubuntu-phablet-jiexi Dockerfile for developing Ubuntu JieXi PDK. 0 [OK] densuke/ubuntu-supervisor densuke/ubuntu-jp-remix:trusty 上で supe... 0 [OK] teamrock/ubuntu TeamRock's Ubuntu image configured with AW... 0 [OK] esycat/ubuntu Ubuntu LTS 0 [OK] 

4 更新自己的Image

容器实际会在Image上增加一个读写文件层，我们可以将已经运行的容器通过docker comit生成新的镜像：

root@gctest:~/.ghostcloud/proxy/conf# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 2d961ac3b9fe ghostcloud.cn:5005/gcali:1.0.7 "/usr/local/ghostclou" 36 hours ago Up 36 hours gcsagent root@gctest:~/.ghostcloud/proxy/conf# docker commit 2d96 ghostcloud:test df9744f284bd8fd778ae7e782f2348ba24e4d9a51877c5e48b2f552fdadb526c root@gctest:~/.ghostcloud/proxy/conf# docker images REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE ghostcloud test df9744f284bd 4 seconds ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.7 553ff90cea5d 40 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.6 0704f2860bd6 41 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.3 746ac51185f2 43 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.2 b06108e12275 43 hours ago 219.6 MB ubuntu latest e9ae3c220b23 3 weeks ago 187.9 MB 

执行命令之后，我们就有了新的镜像。因此，可以通过commit来对容器做快照，是不是很酷？

5 根据Dockerfile编译镜像

通过docker commit可以从一个已有的容器得到镜像，那么如何从头生成一个镜像呢？我们可以通过docker build来进行。首先我们创建一个Dockerfile

root@gctest:~/ghostcloud# cat Dockerfile # This is a comment FROM ubuntu:latest MAINTAINER Shev Yan <yandong@ghostcloud.cn> CMD echo 'hello my image from Dockerfile.' 

接着，我们进入Dockerfile所在的目录，并执行build:

root@gctest:~/ghostcloud# docker build -t myimage . Sending build context to Docker daemon 2.048 kB Step 1 : FROM ubuntu:latest ---> e9ae3c220b23 Step 2 : MAINTAINER Shev Yan <yandong@ghostcloud.cn> ---> Running in 9c78817e17f1 ---> dab9385c6296 Removing intermediate container 9c78817e17f1 Step 3 : CMD echo 'hello my image from Dockerfile.' ---> Running in d8963fe120aa ---> cfcfc50fb4fb Removing intermediate container d8963fe120aa Successfully built cfcfc50fb4fb 

FROM: 表示源自于哪个基础镜像 MAINTAINER: 表示由谁维护 CMD: 表示镜像默认执行的命令

让我们来查看一下新生成的Image:

root@gctest:~/ghostcloud# docker images REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE myimage latest cfcfc50fb4fb About a minute ago 187.9 MB ghostcloud test df9744f284bd 5 minutes ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.7 553ff90cea5d 40 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.6 0704f2860bd6 42 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.3 746ac51185f2 43 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.2 b06108e12275 43 hours ago 219.6 MB ubuntu latest e9ae3c220b23 3 weeks ago 187.9 MB 

运行新生成的镜像：

root@gctest:~/ghostcloud# docker run myimage hello my image from Dockerfile. 

给Image设置tag:

root@gctest:~/ghostcloud# docker tag cfcf myimage:v1 root@gctest:~/ghostcloud# docker images REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE myimage latest cfcfc50fb4fb 8 minutes ago 187.9 MB myimage v1 cfcfc50fb4fb 8 minutes ago 187.9 MB ghostcloud test df9744f284bd 11 minutes ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.7 553ff90cea5d 41 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.6 0704f2860bd6 42 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.3 746ac51185f2 43 hours ago 219.6 MB ghostcloud.cn:5005/gcali 1.0.2 b06108e12275 43 hours ago 219.6 MB ubuntu latest e9ae3c220b23 3 weeks ago 187.9 MB 

6 删除Image

root@gctest:~/ghostcloud# docker rmi myimage:v1 Untagged: myimage:v1