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：
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:/
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
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
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
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
hello my image from Dockerfile.
给Image设置tag:
root@gctest:~/ghostcloud
root@gctest:~/ghostcloud
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
