docker Dockerfile

Posted 2021-09-10 SmallForest

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