docker Dockerfile

Dockerfile

dockerfile是用来构建docker镜像的文件，命令和参数组成的脚本。

构建步骤

1. 编写一个dockerfile文件。名字可以自定义，推荐“Dockerfile”
2. docker build 构建镜像
3. docker run 构建容器
4. docker push 发布镜像（DockerHub 阿里云镜像仓库）

构建镜像过程

1. 每个指令必须大写
2. 执行由上到下

3. 表示注释

4. 每个指令都是一个新的镜像层
   dockerfile是面向开发人员的，docker镜像成为企业交付标准。

dockerfile常用命令

• FROM 基础镜像比如操作系统
• MAINTAINER 维护者信息姓名email smallForest<<[e-mail]>>
• RUN 镜像构建时运行的命令
• ADD 向镜像添加文件，会自动解压tar
• WORKDIR 指定工作目录
• VOLUME 挂载目录
• EXPOSE 暴露端口
• CMD 容器启动时要运行的命令
• ENTRYPOINT 容器启动时要运行的命令，可以追加命令
• ONBUILD 当构建一个被继承的docker，触发该命令
• COPY 类似ADD命令，将文件复制到镜像
• ENV 构建时设置环境变量

之前用别人的镜像，以后自己也可以写镜像。

实践出真知

自己做一个镜像

# 查看当前路径
➜  file pwd
/Users/dada/Downloads/docker-centos/file
➜  file ls
# 创建文件
➜  file touch myDockerfie
# 编辑文件
➜  file vim myDockerfie
# 查看编辑的内容
➜  file cat myDockerfie 
FROM centos
MAINTAINER smallForest<[e-mail]>
ENV MYPATH /usr/local
WORKDIR $MYPATH
RUN yum -y install vim
RUN yum -y install net-tools

EXPOSE 80
CMD echo $MYPATH
CMD echo "----end----"
CMD /bin/bash

# 进行构建镜像，如果文件名字是Dockerfile，则可以不用-f 指定文件路径
➜  file docker build -f myDockerfie -t mycentos03:1.0 .
[+] Building 85.8s (8/8) FINISHED                                                                                                 
 => [internal] load build definition from myDockerfie                                                                        0.0s
 => => transferring dockerfile: 255B                                                                                         0.0s
 => [internal] load .dockerignore                                                                                            0.0s
 => => transferring context: 2B                                                                                              0.0s
 => [internal] load metadata for docker.io/library/centos:latest                                                             0.0s
 => [1/4] FROM docker.io/library/centos                                                                                      0.0s
 => CACHED [2/4] WORKDIR /usr/local                                                                                          0.0s
 => [3/4] RUN yum -y install vim                                                                                            73.6s
 => [4/4] RUN yum -y install net-tools                                                                                      11.3s
 => exporting to image                                                                                                       0.7s 
 => => exporting layers                                                                                                      0.7s 
 => => writing image sha256:13fa3a8f9134f7b7b0e76e2b22ee68d07a09bc1e927365474a66fcc8a3666e6a                                 0.0s 
 => => naming to docker.io/library/mycentos03:1.0                            
# 查看结果
➜  file docker images|grep mycentos03
mycentos03                           1.0                                                     13fa3a8f9134   59 seconds ago   282MB

➜  file docker run -d -it --name mycentos03 mycentos03:1.0
bf6575057cbf0517eeb4ec70d98ef4e232c4246174e4dc15e4f2c1cbd4d917db
➜  file docker ps|grep mycentos03
bf6575057cbf   mycentos03:1.0         "/bin/sh -c /bin/bash"   13 seconds ago   Up 12 seconds   80/tcp                                                 mycentos03
➜  file docker exec -it bf6575057cbf /bin/bash
[root@bf6575057cbf local]# ls
bin  etc  games  include  lib  lib64  libexec  sbin  share  src

# 查看工作目录和设置的/usr/local是否一致
[root@bf6575057cbf local]# pwd
/usr/local
[root@bf6575057cbf local]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.17.0.6  netmask 255.255.0.0  broadcast 172.17.255.255
        ether 02:42:ac:11:00:06  txqueuelen 0  (Ethernet)
        RX packets 9  bytes 726 (726.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@bf6575057cbf local]# vim a.sh
[root@bf6575057cbf local]# 
# 运行结果发现，vim ifconfig是可以使用的，因为yum install进行了安装

• docker history 镜像ID，可以查看镜像的构建历史

  ➜  file docker history 13fa3a8f9134
  IMAGE          CREATED         CREATED BY                                      SIZE      COMMENT
  13fa3a8f9134   8 minutes ago   CMD ["/bin/sh" "-c" "/bin/bash"]                0B        buildkit.dockerfile.v0
  <missing>      8 minutes ago   CMD ["/bin/sh" "-c" "echo \"----end----\""]     0B        buildkit.dockerfile.v0
  <missing>      8 minutes ago   CMD ["/bin/sh" "-c" "echo $MYPATH"]             0B        buildkit.dockerfile.v0
  <missing>      8 minutes ago   EXPOSE map[80/tcp:{}]                           0B        buildkit.dockerfile.v0
  <missing>      8 minutes ago   RUN /bin/sh -c yum -y install net-tools # bu…   14.4MB    buildkit.dockerfile.v0
  <missing>      8 minutes ago   RUN /bin/sh -c yum -y install vim # buildkit    58.1MB    buildkit.dockerfile.v0
  <missing>      39 hours ago    WORKDIR /usr/local                              0B        buildkit.dockerfile.v0
  <missing>      39 hours ago    ENV MYPATH=/usr/local                           0B        buildkit.dockerfile.v0
  <missing>      39 hours ago    MAINTAINER smallForest<[e-mail]>       0B        buildkit.dockerfile.v0
  <missing>      5 months ago    /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B        
  <missing>      5 months ago    /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B        
  <missing>      5 months ago    /bin/sh -c #(nop) ADD file:bd7a2aed6ede423b7…   209MB