dockerfile的使用

àì夳堔傛蜴生んèń 2022-08-29 09:58 135阅读 0赞

# 镜像的分层结构 #

可以看到，新镜像是从base镜像一层一层叠加生成的。每安装一个软件，就在现有镜像的基础上增加一层。为什么Docker镜像要采用这种分层结构呢？

最大的一个好处就是**共享资源**。比如：有多个镜像都从相同的base镜像构建而来，那么Docker Host只需在磁盘上保存一份base镜像；同时内存中也只需加载一份base镜像，就可以为所有容器服务了，而且镜像的每一层都可以被共享。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMjI4MTI4NDk_size_16_color_FFFFFF_t_70]

验证下镜像的分层结构：

# docker export -o hello.tar 578aa8e58724
    # ll
    total 24
    -rw-------. 1 root root 21504 May 28 09:31 hello.tar
    # tar xf hello.tar 
    # ll
    total 40
    drwxr-xr-x. 4 root root    43 May 28 09:07 dev
    drwxr-xr-x. 2 root root    66 May 28 09:07 etc
    -rwxrwxr-x. 1 root root 13336 Mar  5 18:25 hello
    -rw-------. 1 root root 21504 May 28 09:31 hello.tar
    drwxr-xr-x. 2 root root     6 May 28 09:07 proc
    drwxr-xr-x. 2 root root     6 May 28 09:07 sys
    # ./hello 
    
    Hello from Docker!
    This message shows that your installation appears to be working correctly.
    
    To generate this message, Docker took the following steps:
     1. The Docker client contacted the Docker daemon.
     2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
        (amd64)
     3. The Docker daemon created a new container from that image which runs the
        executable that produces the output you are currently reading.
     4. The Docker daemon streamed that output to the Docker client, which sent it
        to your terminal.
    
    To try something more ambitious, you can run an Ubuntu container with:
     $ docker run -it ubuntu bash
    
    Share images, automate workflows, and more with a free Docker ID:
     https://hub.docker.com/
    
    For more examples and ideas, visit:
     https://docs.docker.com/get-started/

# 常用命令 #

<table> 
 <thead> 
  <tr> 
   <th>命令</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>from</td> 
   <td>基础镜像，当前镜像基于（依赖）哪个镜像</td> 
  </tr> 
  <tr> 
   <td>maintainer</td> 
   <td>镜像的维护者和邮箱</td> 
  </tr> 
  <tr> 
   <td>run</td> 
   <td>镜像构建时需要执行的命令</td> 
  </tr> 
  <tr> 
   <td>workdir</td> 
   <td>镜像的工作目录</td> 
  </tr> 
  <tr> 
   <td>expose</td> 
   <td>对外暴露的端口</td> 
  </tr> 
  <tr> 
   <td>env</td> 
   <td>设置环境变量</td> 
  </tr> 
  <tr> 
   <td>add</td> 
   <td>将宿主机的文件复制到镜像中，并自动解压</td> 
  </tr> 
  <tr> 
   <td>copy</td> 
   <td>将宿主机的文件复制到镜像中</td> 
  </tr> 
  <tr> 
   <td>volume</td> 
   <td>容器数据卷，用于数据的保存和持久化</td> 
  </tr> 
  <tr> 
   <td>cmd</td> 
   <td>运行命令，多条CMD只会执行最后一条，参数会被RUN的参数覆盖</td> 
  </tr> 
  <tr> 
   <td>entrypoint</td> 
   <td>运行名令，会把RUN的参数追加到后面</td> 
  </tr> 
 </tbody> 
</table>

## add与copy的区别 ##

add和copy命令都是将宿主机的文件拷贝到镜像中，区别在于add会自动解压压缩文件，而copy不会，如果要在容器内部复制文件，可以使用run copy xx oo。

# 实战 #

## 构建JDK8镜像 ##

1、从oracle官网下载JDK的压缩包至/usr/local目录下

2、编写Dockerfile文件：

# cat jdk8.dockerfile
    from centos
    
    maintainer morris131<morris131@163.com>
    
    env WORK_DIR /usr/local
    
    workdir $WORK_DIR
    
    add jdk-8u241-linux-x64.tar.gz $WORK_DIR
    
    env JAVA_HOME $WORK_DIR/jdk1.8.0_241
    
    env PATH $PATH:$JAVA_HOME/bin

3、构建镜像

# docker build -f jdk8.dockerfile -t jdk:8 .
    Sending build context to Docker daemon  278.5MB
    Step 1/7 : from centos
    latest: Pulling from library/centos
    7a0437f04f83: Pull complete
    Digest: sha256:5528e8b1b1719d34604c87e11dcd1c0a20bedf46e83b5632cdeac91b8c04efc1
    Status: Downloaded newer image for centos:latest
     ---> 300e315adb2f
    Step 2/7 : maintainer morris131<morris131@163.com>
     ---> Running in 4257998a4ff9
    Removing intermediate container 4257998a4ff9
     ---> 7ee01d673adf
    Step 3/7 : env WORK_DIR /usr/local
     ---> Running in 463cc056923f
    Removing intermediate container 463cc056923f
     ---> 5815faeb29c0
    Step 4/7 : workdir $WORK_DIR
     ---> Running in c05d4646c2bc
    Removing intermediate container c05d4646c2bc
     ---> 46262df00d54
    Step 5/7 : add jdk-8u241-linux-x64.tar.gz $WORK_DIR
     ---> 788d7864c96d
    Step 6/7 : env JAVA_HOME $WORK_DIR/jdk1.8.0_241
     ---> Running in e9df92926e78
    Removing intermediate container e9df92926e78
     ---> b048814c5036
    Step 7/7 : env PATH $PATH:$JAVA_HOME/bin
     ---> Running in 5c73a80ce917
    Removing intermediate container 5c73a80ce917
     ---> 1292374176fe
    Successfully built 1292374176fe
    Successfully tagged jdk:8

docker build参数说明：

*  \-f：Dockfile的路径
 *  \-t：指定生成的镜像的名称与标签
 *  最后一个点代表生成镜像的目录为当前目录。

4、查看生成的镜像

# docker images
    REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
    jdk                 8                   1292374176fe        5 hours ago         613MB
    centos              latest              300e315adb2f        7 months ago        209MB

5、使用镜像生成容器，检验容器的java环境是否正确。

# docker run --name jdk8 -itd jdk:8
    51dc5cd5814f9916058d096ca211c975e70e43913b5f9afe170533da0bc9eeb4
    # docker ps
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
    51dc5cd5814f        jdk:8               "/bin/bash"         4 seconds ago       Up 4 seconds                            jdk8
    # docker exec -it 51dc5cd5814f bash
    # java -version
    java version "1.8.0_241"
    Java(TM) SE Runtime Environment (build 1.8.0_241-b07)
    Java HotSpot(TM) 64-Bit Server VM (build 25.241-b07, mixed mode)

6、最后可以将镜像推送到远程仓库，供后续使用。

# docker login --username=xxxxx registry.cn-hangzhou.aliyuncs.com
    Password:
    Login Succeeded
    # docker tag jdk:8 registry.cn-hangzhou.aliyuncs.com/morris131/jdk:8
    # docker images
    REPOSITORY                                        TAG                 IMAGE ID            CREATED             SIZE
    registry.cn-hangzhou.aliyuncs.com/morris131/jdk   8                   1292374176fe        5 hours ago         613MB
    jdk                                               8                   1292374176fe        5 hours ago         613MB
    centos                                            latest              300e315adb2f        7 months ago        209MB
    # docker push registry.cn-hangzhou.aliyuncs.com/morris131/jdk:8
    The push refers to repository [registry.cn-hangzhou.aliyuncs.com/morris131/jdk]
    d9e9da3e57ad: Pushed
    2653d992f4ef: Layer already exists
    8: digest: sha256:fdd432272e0b56388c1e72e4f6db91e4d6e264351f7b85e544fe864cff0bc50c size: 742

在其他地方就可以通过下面的命令下载镜像了：

# docker pull registry.cn-hangzhou.aliyuncs.com/morris131/jdk:[镜像版本号]

可以使用docker history查询镜像的构建过程：

# docker history jdk:8
    IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
    1292374176fe        5 hours ago         /bin/sh -c #(nop) ENV PATH=/usr/local/sbin:… 0B
    b048814c5036        5 hours ago         /bin/sh -c #(nop) ENV JAVA_HOME=/usr/local/… 0B
    788d7864c96d        5 hours ago         /bin/sh -c #(nop) ADD file:b52d9155076771228… 404MB
    46262df00d54        5 hours ago         /bin/sh -c #(nop) WORKDIR /usr/local 0B
    5815faeb29c0        5 hours ago         /bin/sh -c #(nop) ENV WORK_DIR=/usr/local 0B
    7ee01d673adf        5 hours ago         /bin/sh -c #(nop) MAINTAINER morris131<morr… 0B

## 构建zookeeper镜像 ##

1、将zookeeper的压缩包从官网下载至/usr/local目录下。

2、编写dockerfile文件：

# cat zookeeper.dockerfile
    from registry.cn-hangzhou.aliyuncs.com/morris131/jdk:8
    
    maintainer morris131<morris131@163.com>
    
    env WORK_DIR /usr/local
    
    workdir $WORK_DIR
    
    add apache-zookeeper-3.6.3-bin.tar.gz $WORK_DIR
    
    env ZK_HOME $WORK_DIR/apache-zookeeper-3.6.3-bin
    
    env PATH $PATH:$ZK_HOME/bin
    
    run cp $ZK_HOME/conf/zoo_sample.cfg $ZK_HOME/conf/zoo.cfg
    
    expose 2181
    
    # 一定要以前台方式运行，否则容器启动后会自动关闭
    entrypoint zkServer.sh start-foreground

3、其他步骤与构建jdk的一样。

## 构建kafka镜像 ##

# cat kafka.dockerfile
    from registry.cn-hangzhou.aliyuncs.com/morris131/zookeeper:3.6.3
    
    env WORK_DIR /usr/local
    
    workdir $WORK_DIR
    
    add kafka_2.13-2.8.0.tgz $WORK_DIR
    
    env KAFKA_HOME $WORK_DIR/kafka_2.13-2.8.0
    
    env PATH $PATH:$KAFKA_HOME/bin
    
    expose 9002
    
    run echo "#!/bin/bash" > $WORK_DIR/entrypoint.sh && \
    echo "/bin/bash zkServer.sh start" >> $WORK_DIR/entrypoint.sh && \
    echo "/bin/bash $KAFKA_HOME/bin/kafka-server-start.sh $KAFKA_HOME/config/server.properties" >> $WORK_DIR/entrypoint.sh
    
    entrypoint ["/bin/bash", "/usr/local/entrypoint.sh"]

注意：如果启动多个服务，前面的服务一定要在后台运行，最后一个服务要以前台运行。否则，全部以前台运行的话，只有第一个服务会启动；全部以后台运行的话，当最后一个服务执行完成后，容器就退出了。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMjI4MTI4NDk_size_16_color_FFFFFF_t_70]: /images/20220829/cba1cfa75c0342b5a7d826551162d2fa.png