DockerFile详解及应用

一、定义

Dockerfile是用来构建Docker镜像的文本文件，是由一条条构建镜像所需的指令和参数构成的脚本。

二、使用DockerFile构建镜像

image.png

1.构建步骤

• 编写Dockerfile文件
• docker build构建镜像
• docker run 依镜像运行容器实例

2.执行流程：

• docker从基础镜像运行一个容器
• 执行一条指令并对容器作出修改
• 执行类似docker commit的操作提交一个新的镜像层
• docker再基于刚提交的镜像运行一个新容器
• 执行dockerfile中的下一条指令直到所有指令都执行完成

FROM alpine：latest 4e38e38c7ct0
MAINTAINER hcx   fb1gail4315b
CMD echo 'hello docker' 8gf243gsfe8

镜像分层.png

3.三者关系

image.png

三、DockerFile常用保留字指令

命令	用途
FROM	base image ，指定一个基础镜像；（当前新镜像是基于哪个镜像的，指定一个已经存在的镜像作为模板，第一条必须是from）
RUN	执行命令 ，在容器内执行一个命令；（在 docker build时运行）
ADD	添加文件（将宿主机目录下的文件拷贝进镜像且会自动处理URL和解压tar压缩包）
COPY	拷贝文件（类似ADD，拷贝宿主机的文件/目录到镜像中）
CMD	执行命令 （指定容器启动后的要干的事情，在docker run 时运行）
EXPOSE	暴露端口（当前容器对外暴露出的端口）
WORKDIR	指定命令运行的路径；（指定在创建容器后，终端默认登陆的进来工作目录，一个落脚点）
MAINTAINER	维护者，镜像维护者的姓名和邮箱地址
ENV	设定环境变量（在构建镜像过程中设置环境变量）
ENTRYPOINT	容器入口，指定一个容器启动时要运行的命令
USER	指定用户，指定执行该命令的用户；（指定该镜像以什么样的用户去执行，如果都不指定，默认是root）
VOLUME	mount point，指定容器所挂载的卷；（用于数据保存和持久化工作）

• 每条保留字指令都必须为大写字母且后面要跟随至少一个参数
• 指令按照从上到下，顺序执行
• 每条指令都会创建一个新的镜像层并对镜像进行提交

1.RUN命令

• shell格式: RUN <命令行命令>
• exec格式: RUN ["可执行文件","参数1","参数2"]

2.ENV命令

• 声明：ENV MY_PATH /usr/hcx
• 使用：WORKDIR $MY_PATH

3.CMD命令

指定容器启动后要运行的命令。

• shell格式:CMD <命令>
• exec格式: CMD ["可执行文件","参数1","参数2",···]
• 参数列表：CMD ["参数1","参数2",····]；在指定了ENTRYPOINT指令后，用CMD指定具体的参数。
  CMD指令可以有多个，但只有最后一个生效，CMD会被 docker run 之后的参数替换

4.ENTRYPOINT命令

指定容器启动后要运行的命令。类似CMD，但是ENTRYPOINT不会被docker run后面的命令覆盖，这些命令行参数会被当作参数传递给ENTRYPOINT指令指定的程序。

• ENTRYPOINT["executeable","<param1>","<param1>",···]

即CMD等同于给ENTRYPOINT传参。当指定了ENTRYPOINT后，CMD的内容会作为参数传递给ENTRYPOINT指令：[<ENTRYPOINT>"<CMD>"]

FROM nginx

ENTRYPOINT ["nginx","-c"]
CMD ["/etc/nginx/nginx.conf"]

• 不加参数正常运行：nginx -c /etc/nginx/nginx.conf
• 手动加参数运行：docker run nginx -c /etc/nginx/nginx1.conf 就会变成：nginx -c /etc/nginx/nginx1.conf，即nginx1.conf会覆盖掉原本的nginx.conf

Dockerfile 中可以有多个 CMD 指令，但只有最后一个生效，CMD 会被 docker run 之后的参数替换

demo：
redis的dockerfile（部分内容）：

FROM debian:bullseye-slim # 基于debian:bullseye-slim镜像构建
RUN groupadd -r -g 999 redis && useradd -r -g redis -u 999 redis

# 环境变量 可以在后续的run命令中使用  key-value $key来引用变量 例：$GOSU_VERSION等同于1.16
ENV GOSU_VERSION 1.16
ENV REDIS_VERSION 6.2.12
ENV REDIS_DOWNLOAD_URL http://download.redis.io/releases/redis-6.2.12.tar.gz
ENV REDIS_DOWNLOAD_SHA 75352eef41e97e84bfa94292cbac79e5add5345fc79787df5cbdff703353fb1b

RUN mkdir /data && chown redis:redis /data
VOLUME /data
WORKDIR /data # 容器创建成功后，通过终端登录进来默认在/data目录下

COPY docker-entrypoint.sh /usr/local/bin/ # 拷贝docker-entrypoint.sh到镜像中的/usr/local/bin/
ENTRYPOINT ["docker-entrypoint.sh"]

EXPOSE 6379 # 容器暴露6379端口
CMD ["redis-server"]

四、自定义镜像

在基础的centos镜像上安装java环境。

1.编写Dockerfile文件：

Dockerfile:

# 基于centos
FROM centos:7
MAINTAINER hcx<hcx@qq.com>

ENV MYPATH /usr/local
WORKDIR $MYPATH

# 安装java8
RUN yum -y install glibc.i686
RUN mkdir /usr/local/java

# 将宿主机的文件jdk-8u351-linux-x64.tar.gz 解压添加到容器的 /usr/local/java下
ADD jdk-8u351-linux-x64.tar.gz /usr/local/java

# 配置环境变量
ENV JAVA_HOME /usr/local/java/jdk1.8.0_351
ENV JRE_HOME $JAVA_HOME/jre
ENV CLASSPATH $JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib:$CLASSPATH
ENV PATH $JAVA_HOME/bin:$PATH

EXPOSE 80

CMD echo $MYPATH
CMD echo "install centos success--------------ok"
CMD /bin/bash

2.构建镜像 docker build -t 新镜像名字:TAG .

在宿主机上运行：
在docker文件夹下准备好Dockerfile和对应的资源：

hongcaixia@hongcaixiadeMacBook-Pro Documents % cd docker
hongcaixia@hongcaixiadeMacBook-Pro docker % ls
Dockerfile          jdk-8u351-linux-x64.tar.gz

hongcaixia@hongcaixiadeMacBook-Pro docker % docker build -t centos-java8:1.0 . 
[+] Building 15.6s (10/10) FINISHED                                                                                                                                                                         
 => [internal] load build definition from Dockerfile                                                                                                                                                   0.0s
 => => transferring dockerfile: 745B                                                                                                                                                                   0.0s
 => [internal] load .dockerignore                                                                                                                                                                      0.0s
 => => transferring context: 2B                                                                                                                                                                        0.0s
 => [internal] load metadata for docker.io/library/centos:7                                                                                                                                           15.4s
 => [1/5] FROM docker.io/library/centos:7@sha256:9d4bcbbb213dfd745b58be38b13b996ebb5ac315fe75711bd618426a630e0987                                                                                      0.0s
 => [internal] load build context                                                                                                                                                                      0.0s
 => => transferring context: 190B                                                                                                                                                                      0.0s
 => CACHED [2/5] WORKDIR /usr/local                                                                                                                                                                    0.0s
 => CACHED [3/5] RUN yum -y install glibc.i686                                                                                                                                                         0.0s
 => CACHED [4/5] RUN mkdir /usr/local/java                                                                                                                                                             0.0s
 => CACHED [5/5] ADD jdk-8u351-linux-x64.tar.gz /usr/local/java                                                                                                                                        0.0s
 => exporting to image                                                                                                                                                                                 0.0s
 => => exporting layers                                                                                                                                                                                0.0s
 => => writing image sha256:ed61e051f801980577988e66ac8c31b9a63844ad8f2b078aa9b36232699741b9                                                                                                           0.0s
 => => naming to docker.io/library/centos-java8:1.0                                                                                                                                                    0.0s

Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them
hongcaixia@hongcaixiadeMacBook-Pro docker % 

hongcaixia@hongcaixiadeMacBook-Pro docker % docker images
REPOSITORY                                      TAG       IMAGE ID       CREATED         SIZE
centos-java8                                    1.0       ed61e051f801   11 hours ago    830MB
bitnami/kafka                                   latest    e7e7893c6d36   4 months ago    552MB
zookeeper                                       latest    248549379309   6 months ago    300MB
xuxueli/xxl-job-admin                           2.3.1     252b168021da   12 months ago   237MB
nginx                                           latest    605c77e624dd   17 months ago   141MB
redis                                           latest    7614ae9453d1   18 months ago   113MB
apacherocketmq/rocketmq-dashboard               latest    eae6c5db5d11   19 months ago   738MB
hello-world                                     latest    feb5d9fea6a5   20 months ago   13.3kB
centos                                          latest    300e315adb2f   2 years ago     209MB
docker.elastic.co/kibana/kibana                 7.1.0     714b175e84e8   4 years ago     745MB
docker.elastic.co/elasticsearch/elasticsearch   7.1.0     12ad640a1ec0   4 years ago     894MB
lmenezes/cerebro                                0.8.3     3a2daf87f0c7   4 years ago     333MB
hongcaixia@hongcaixiadeMacBook-Pro docker %

3.运行镜像 docker run -it 新镜像名字:TAG

hongcaixia@hongcaixiadeMacBook-Pro docker % docker run -it centos-java8:1.0
[root@5e4d9b15417d local]# java -version
java version "1.8.0_351"
Java(TM) SE Runtime Environment (build 1.8.0_351-b10)
Java HotSpot(TM) 64-Bit Server VM (build 25.351-b10, mixed mode)
[root@5e4d9b15417d local]# 

五、使用DockerFile构建微服务

1.代码

添加依赖：

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

    </dependencies>

MyController:

package com.hcx.dockerfiledemo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @Title: MyController.java
 * @Package com.hcx.dockerfiledemo.controller
 * @Description: (用一句话描述该文件做什么)
 * @Author: hongcaixia
 * @Date: 2023/6/15 21:35
 * @Version V1.0
 */
@RestController
@RequestMapping(value = "/my")
public class MyController {

    @GetMapping("/test")
    public String test() {
        return "hello,world";
    }
}

2.编写Dockerfile

# 基于centos
FROM java:8
MAINTAINER hcx<hcx@qq.com>

# 指定临时文件目录为/tmp 在主机/var/lib/docker目录下创建了一个临时文件并链接到容器的/tmp
VOLUME /tmp

# 将jar包添加到容器并更名为 hcx-docker.jar
ADD dockerfile-demo-0.0.1-SNAPSHOT.jar hcx-docker.jar

# 运行jar
RUN bash -c 'touch /hcx-docker.jar'
ENTROYPOINT ["java","-jar","/hcx-docker.jar"]

# 暴露80端口
EXPOSE 80

3.构建镜像 docker build -t 新镜像名字:TAG .

hongcaixia@hongcaixiadeMacBook-Pro docker % cd java
hongcaixia@hongcaixiadeMacBook-Pro java % ls
Dockerfile              dockerfile-demo-0.0.1-SNAPSHOT.jar
hongcaixia@hongcaixiadeMacBook-Pro java % docker build -t hcx-docker:1.0 .
[+] Building 2.1s (8/8) FINISHED                                                                                                                                                                            
 => [internal] load build definition from Dockerfile                                                                                                                                                   0.0s
 => => transferring dockerfile: 785B                                                                                                                                                                   0.0s
 => [internal] load .dockerignore                                                                                                                                                                      0.0s
 => => transferring context: 2B                                                                                                                                                                        0.0s
 => [internal] load metadata for docker.io/library/java:8                                                                                                                                              1.0s
 => [internal] load build context                                                                                                                                                                      0.4s
 => => transferring context: 17.70MB                                                                                                                                                                   0.4s
 => [1/3] FROM docker.io/library/java:8@sha256:c1ff613e8ba25833d2e1940da0940c3824f03f802c449f3d1815a66b7f8c0e9d                                                                                        0.3s
 => => resolve docker.io/library/java:8@sha256:c1ff613e8ba25833d2e1940da0940c3824f03f802c449f3d1815a66b7f8c0e9d                                                                                        0.0s
 => => sha256:c1ff613e8ba25833d2e1940da0940c3824f03f802c449f3d1815a66b7f8c0e9d 2.00kB / 2.00kB                                                                                                         0.0s
 => => sha256:d23bdf5b1b1b1afce5f1d0fd33e7ed8afbc084b594b9ccf742a5b27080d8a4a8 4.73kB / 4.73kB                                                                                                         0.0s
 => [2/3] ADD dockerfile-demo-0.0.1-SNAPSHOT.jar hcx-docker.jar                                                                                                                                        0.1s
 => [3/3] RUN bash -c 'touch /hcx-docker.jar'                                                                                                                                                          0.4s
 => exporting to image                                                                                                                                                                                 0.1s
 => => exporting layers                                                                                                                                                                                0.1s
 => => writing image sha256:2c8e8a4cedccca75b565b93fe411a40d1885ddd30b43beb57ecc9bba02b797f9                                                                                                           0.0s
 => => naming to docker.io/library/hcx-docker:1.0                                                                                                                                                      0.0s

Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them

hongcaixia@hongcaixiadeMacBook-Pro java % docker images
REPOSITORY                                      TAG       IMAGE ID       CREATED         SIZE
hcx-docker                                      1.0       2c8e8a4cedcc   2 minutes ago   679MB
centosjava8                                     latest    e90626d6775b   24 hours ago    830MB
centos-java8                                    1.0       ed61e051f801   24 hours ago    830MB
bitnami/kafka                                   latest    e7e7893c6d36   5 months ago    552MB
zookeeper                                       latest    248549379309   6 months ago    300MB
xuxueli/xxl-job-admin                           2.3.1     252b168021da   13 months ago   237MB
nginx                                           latest    605c77e624dd   17 months ago   141MB
redis                                           latest    7614ae9453d1   18 months ago   113MB
apacherocketmq/rocketmq-dashboard               latest    eae6c5db5d11   19 months ago   738MB
hello-world                                     latest    feb5d9fea6a5   20 months ago   13.3kB
centos                                          latest    300e315adb2f   2 years ago     209MB
docker.elastic.co/kibana/kibana                 7.1.0     714b175e84e8   4 years ago     745MB
docker.elastic.co/elasticsearch/elasticsearch   7.1.0     12ad640a1ec0   4 years ago     894MB
lmenezes/cerebro                                0.8.3     3a2daf87f0c7   4 years ago     333MB
hongcaixia@hongcaixiadeMacBook-Pro java % 

4.运行镜像 docker run -it 新镜像名字:TAG

hongcaixia@hongcaixiadeMacBook-Pro java % docker images
REPOSITORY                                      TAG       IMAGE ID       CREATED         SIZE
hcx-docker                                      1.0       2c8e8a4cedcc   2 minutes ago   679MB
centosjava8                                     latest    e90626d6775b   24 hours ago    830MB
centos-java8                                    1.0       ed61e051f801   24 hours ago    830MB
bitnami/kafka                                   latest    e7e7893c6d36   5 months ago    552MB
zookeeper                                       latest    248549379309   6 months ago    300MB
xuxueli/xxl-job-admin                           2.3.1     252b168021da   13 months ago   237MB
nginx                                           latest    605c77e624dd   17 months ago   141MB
redis                                           latest    7614ae9453d1   18 months ago   113MB
apacherocketmq/rocketmq-dashboard               latest    eae6c5db5d11   19 months ago   738MB
hello-world                                     latest    feb5d9fea6a5   20 months ago   13.3kB
centos                                          latest    300e315adb2f   2 years ago     209MB
docker.elastic.co/kibana/kibana                 7.1.0     714b175e84e8   4 years ago     745MB
docker.elastic.co/elasticsearch/elasticsearch   7.1.0     12ad640a1ec0   4 years ago     894MB
lmenezes/cerebro                                0.8.3     3a2daf87f0c7   4 years ago     333MB
hongcaixia@hongcaixiadeMacBook-Pro java % docker run -d -p 8080:8080 2c8e8a4cedcc
ef2afc6e7cb7658e1cb0df788d0c23b85e2fded3c0091288e624088526a6d31f
hongcaixia@hongcaixiadeMacBook-Pro java % docker ps
CONTAINER ID   IMAGE          COMMAND                  CREATED          STATUS          PORTS                               NAMES
ef2afc6e7cb7   2c8e8a4cedcc   "java -jar /hcx-dock…"   41 seconds ago   Up 41 seconds   0.0.0.0:80->80/tcp, :::80->80/tcp   stoic_khorana
hongcaixia@hongcaixiadeMacBook-Pro java % 

5.访问测试

hongcaixia@hongcaixiadeMacBook-Pro java % curl 127.0.0.1:8080/my/test
hello,world%                                                                                                                                                                                                hongcaixia@hongcaixiadeMacBook-Pro java %