使用 docker 创建自己的镜像

docker run 命令

镜像（image）：An image is a filesystem and parameters to use at runtime. It doesn’t have state and never changes

容器（container): A container is a running instance of an image.

简言之，容器是镜像的实例。

运行命令的时候，执行如下步骤：

1 检查是否有名叫 hello-world 软件镜像（image）

2 如果没有，则从 docker hub 上下载

3 加载该镜像（image)到 容器（container）中，并运行

创建自己的镜像 image

首先运行 docker run docker/whalesay cowsay boo-boo

下载运行 docker hub 上的 whalesay 镜像。

- 创建一个 Dockerfile 文件

添加如下命令到文件中：

FROM docker/whalesay:latest （告诉docker当前的image是依靠于哪个image生成的）
RUN apt-get -y update && apt-get install -y fortunes（whalesay 镜像是基于ubuntu的，使用apt-get install来安装packages. 这两个命令更新了packages包，并安装了fortune 程序）
CMD /usr/games/fortune -a | cowsay（告诉镜像image在环境设置好以后的最后一个命令，该命令运行了furtune -a,并将输出发给额cowsay命令）

到这里，一个基本的Dockerfile就创建好了

- 根据 Dockerfile 来 Build 镜像

使用 docker build 命令来来创建镜像

-t 参数，给创建的镜像命名（give a tag）

. 不要忘记这个命令（就是一个英文句号），告诉 docker build 查找当前目录里的 dockerfile 文件。

$ docker build -t docker-whale .

 

Sending build context to Docker daemon 2.048 kB

...snip...

Removing intermediate container cb53c9d09f3b

Successfully built c2c3152907b5

1. Docker检查确认所有build所需都齐了,输出如下消息：

   Sending build context to Docker daemon 2.048 kB
   

2. Docker 检查 whalesay image 是否存在，不存在则从Docker Hub上pull下来。

   Step 1 : FROM docker/whalesay:latest
    ---> 6b362a9f73eb
   

   在每一步结束，都会有一个ID被打印出来。这个ID是每一步创建出的 Layer 的ID。 Dockerfile 中每一行命令都和 image 中的一个 Layer 相关。你自己的ID会显示的不一样。

3. Docker 创建一个临时容器 container 来运行 whalesay 镜像image。在这个临时容器中，Docker 运行 Dockerfile中的下一条命令, 即 RUN 命令。这会安装 fortune 。这里会有很多输出，就和在 Ubuntu 中创建出来的消息一样。

   Step 2 : RUN apt-get -y update && apt-get install -y fortunes
    ---> Running in 05d4eda04526
   Ign http://archive.ubuntu.com trusty InRelease
   Get:1 http://archive.ubuntu.com trusty-updates InRelease [65.9 kB]
   Get:2 http://archive.ubuntu.com trusty-security InRelease [65.9 kB]
   Hit http://archive.ubuntu.com trusty Release.gpg
   Hit http://archive.ubuntu.com trusty Release
   Get:3 http://archive.ubuntu.com trusty-updates/main Sources [480 kB]
   Get:4 http://archive.ubuntu.com trusty-updates/restricted Sources [5921 B]
   Get:5 http://archive.ubuntu.com trusty-updates/universe Sources [214 kB]
   Get:6 http://archive.ubuntu.com trusty-updates/main amd64 Packages [1160 kB]
   Get:7 http://archive.ubuntu.com trusty-updates/restricted amd64 Packages [20.4 kB]
   Get:8 http://archive.ubuntu.com trusty-updates/universe amd64 Packages [505 kB]
   Get:9 http://archive.ubuntu.com trusty-security/main Sources [157 kB]
   Get:10 http://archive.ubuntu.com trusty-security/restricted Sources [4621 B]
   Get:11 http://archive.ubuntu.com trusty-security/universe Sources [54.5 kB]
   Get:12 http://archive.ubuntu.com trusty-security/main amd64 Packages [700 kB]
   Get:13 http://archive.ubuntu.com trusty-security/restricted amd64 Packages [17.0 kB]
   Get:14 http://archive.ubuntu.com trusty-security/universe amd64 Packages [191 kB]
   Hit http://archive.ubuntu.com trusty/main Sources
   Hit http://archive.ubuntu.com trusty/restricted Sources
   Hit http://archive.ubuntu.com trusty/universe Sources
   Hit http://archive.ubuntu.com trusty/main amd64 Packages
   Hit http://archive.ubuntu.com trusty/restricted amd64 Packages
   Hit http://archive.ubuntu.com trusty/universe amd64 Packages
   Fetched 3640 kB in 11s (329 kB/s)
   Reading package lists...
   Reading package lists...
   Building dependency tree...
   Reading state information...
   The following extra packages will be installed:
     fortune-mod fortunes-min librecode0
   Suggested packages:
     x11-utils bsdmainutils
   The following NEW packages will be installed:
     fortune-mod fortunes fortunes-min librecode0
   0 upgraded, 4 newly installed, 0 to remove and 92 not upgraded.
   Need to get 1961 kB of archives.
   After this operation, 4817 kB of additional disk space will be used.
   Get:1 http://archive.ubuntu.com/ubuntu/ trusty/main librecode0 amd64 3.6-21 [771 kB]
   Get:2 http://archive.ubuntu.com/ubuntu/ trusty/universe fortune-mod amd64 1:1.99.1-7 [39.5 kB]
   Get:3 http://archive.ubuntu.com/ubuntu/ trusty/universe fortunes-min all 1:1.99.1-7 [61.8 kB]
   Get:4 http://archive.ubuntu.com/ubuntu/ trusty/universe fortunes all 1:1.99.1-7 [1089 kB]
   debconf: unable to initialize frontend: Dialog
   debconf: (TERM is not set, so the dialog frontend is not usable.)
   debconf: falling back to frontend: Readline
   debconf: unable to initialize frontend: Readline
   debconf: (This frontend requires a controlling tty.)
   debconf: falling back to frontend: Teletype
   dpkg-preconfigure: unable to re-open stdin:
   Fetched 1961 kB in 19s (101 kB/s)
   Selecting previously unselected package librecode0:amd64.
   (Reading database ... 13116 files and directories currently installed.)
   Preparing to unpack .../librecode0_3.6-21_amd64.deb ...
   Unpacking librecode0:amd64 (3.6-21) ...
   Selecting previously unselected package fortune-mod.
   Preparing to unpack .../fortune-mod_1%3a1.99.1-7_amd64.deb ...
   Unpacking fortune-mod (1:1.99.1-7) ...
   Selecting previously unselected package fortunes-min.
   Preparing to unpack .../fortunes-min_1%3a1.99.1-7_all.deb ...
   Unpacking fortunes-min (1:1.99.1-7) ...
   Selecting previously unselected package fortunes.
   Preparing to unpack .../fortunes_1%3a1.99.1-7_all.deb ...
   Unpacking fortunes (1:1.99.1-7) ...
   Setting up librecode0:amd64 (3.6-21) ...
   Setting up fortune-mod (1:1.99.1-7) ...
   Setting up fortunes-min (1:1.99.1-7) ...
   Setting up fortunes (1:1.99.1-7) ...
   Processing triggers for libc-bin (2.19-0ubuntu6.6) ...
    ---> dfaf993d4a2e
   Removing intermediate container 05d4eda04526
   

   RUN 结束，有一个 layer 会被创建，并且之前创建的临时容器 container 也被去除了。

4. 一个新的临时容器 container 被创建出来，Docker 为CMD命令添加一个 Layer，然后在移除该容器 congtainer

   Step 3 : CMD /usr/games/fortune -a | cowsay
    ---> Running in a8e6faa88df3
    ---> 7d9495d03763
   Removing intermediate container a8e6faa88df3
   Successfully built 7d9495d03763
   

到这里，我们就创建了一个自己的镜像 image，名叫 docker-whale.

接下来直接运行 docker run docker-whale

来源： https://docs.docker.com/engine/getstarted/step_four/

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