这篇文章主要介绍“什么是Dockerfile”，在日常操作中，相信很多人在什么是Dockerfile问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”什么是Dockerfile”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
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一 DockerFile构建过程解析
1.Dockerfile内容基础知识
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
#表示注释
每条指令都会创建一个新的镜像层，并对镜像进行提交
2 Docker执行Dockerfile的大致流程
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
3 小总结
从应用软件的角度来看，Dockerfile、Docker镜像与Docker容器分别代表软件的三个不同阶段，
Dockerfile，需要定义一个Dockerfile，Dockerfile定义了进程需要的一切东西。Dockerfile涉及的内容包括执行代码或者是文件、环境变量、依赖包、运行时环境、动态链接库、操作系统的发行版、服务进程和内核进程(当应用进程需要和系统服务和内核进程打交道，这时需要考虑如何设计namespace的权限控制)等等;
Docker镜像，在用Dockerfile定义一个文件之后，docker build时会产生一个Docker镜像，当运行 Docker镜像时，会真正开始提供服务;
Docker容器，容器是直接提供服务的。
二 DockerFile体系结构（保留字指令）
FROM
基础镜像，当前新镜像是基于哪个镜像的
MAINTAINER
镜像维护者的姓名和邮箱地址
RUN
容器构建时需要运行的命令
EXPOSE
当前容器对外暴露出的端口
WORKDIR
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
ENV
用来在构建镜像过程中设置环境变量
例如：ENV MY_PATH /usr/mytest 这个环境变量可以在后续的任何RUN指令中使用，这就如同在命令前面指定了环境变量前缀一样；也可以在其它指令中直接使用这些环境变量， 比如：WORKDIR $MY_PATH
ADD
将宿主机目录下的文件拷贝进镜像且ADD命令会自动处理URL和解压tar压缩包
COPY
类似ADD，拷贝文件和目录到镜像中。 将从构建上下文目录中 <源路径> 的文件/目录复制到新的一层的镜像内的 <目标路径> 位置
VOLUME
容器数据卷，用于数据保存和持久化工作
CMD
指定一个容器启动时要运行的命令
三 案例
Base镜像（scratch）
Docker Hub 中 99% 的镜像都是通过在 base 镜像中安装和配置需要的软件构建出来的
自定义镜像 mycentos
1 编写
Hub默认CentOS镜像的情况
myCentOS内容Dockerfile
FROM centos
MAINTAINER zhl<253316343@qq.com>
ENV MYPATH /usr/local
WORKDIR $MYPATH
RUN yum -y install vim
RUN yum -y install net-tools
EXPOSE 80
CMD echo $MYPATH
CMD echo "success ------ ok"
CMD /bin/bash
2 构建
docker build -f DockerFile目录 -t 新镜像名字:TAG . . 表示当前目录
docker build -f /opt/docker/mydocker/Dockerfile -t zhl/centos1.1 .
root@zhanghl:/opt/docker/mydocker# docker build -f /opt/docker/mydocker/Dockerfile -t zhl/centos1.1 .
Sending build context to Docker daemon 2.048kB
Step 1/10 : FROM centos
---> 300e315adb2f
Step 2/10 : MAINTAINER zhl<253316343@qq.com>
---> Running in 9cef0b83aa4d
Removing intermediate container 9cef0b83aa4d
---> e03c70aa84dd
Step 3/10 : ENV MYPATH /usr/local
---> Running in a06eb1e589da
Removing intermediate container a06eb1e589da
---> f817774de33b
Step 4/10 : WORKDIR $MYPATH
---> Running in 2638200252e1
Removing intermediate container 2638200252e1
---> e0ac249d8189
Step 5/10 : RUN yum -y install vim
---> Running in 23a14562d0d6
.......
---> 059822073508
Step 6/10 : RUN yum -y install net-tools
---> Running in 4a437d96a483
.....
---> c49737740d20
Step 7/10 : EXPOSE 80
---> Running in 326caf878a8e
Removing intermediate container 326caf878a8e
---> 6690abcca60f
Step 8/10 : CMD echo $MYPATH
---> Running in 47664a0e6e10
Removing intermediate container 47664a0e6e10
---> 8db1cff1fad3
Step 9/10 : CMD echo "success ------ ok"
---> Running in 7ad2234cdfbd
Removing intermediate container 7ad2234cdfbd
---> a08723e08f62
Step 10/10 : CMD /bin/bash
---> Running in e0ecfa0bf1f3
Removing intermediate container e0ecfa0bf1f3
---> 77c006bf4b15
Successfully built 77c006bf4b15
Successfully tagged zhl/centos1.1:latest
root@zhanghl:/opt/docker/mydocker#
3 运行
docker run -it 新镜像名字：TAG .
root@zhanghl:/opt/docker/mydocker# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
zhl/centos1.1 latest 77c006bf4b15 3 minutes ago 291MB
zhl/centos latest e4998e64dece 38 hours ago 209MB
zhl/mytomcat 1.1 a636ea3caaed 4 days ago 672MB
mongo latest 995ccc33e58f 8 days ago 449MB
tomcat latest c0e850d7b9bb 9 days ago 667MB
hello-world latest d1165f221234 8 weeks ago 13.3kB
centos latest 300e315adb2f 4 months ago 209MB
root@zhanghl:/opt/docker/mydocker# docker run -it 77c006bf4b15
[root@01ba3472d1c3 local]# pwd
/usr/local
[root@01ba3472d1c3 local]# ifconfig
eth0: flags=4163 mtu 1500
inet 172.17.0.2 netmask 255.255.0.0 broadcast 172.17.255.255
ether 02:42:ac:11:00:02 txqueuelen 0 (Ethernet)
RX packets 21 bytes 2716 (2.6 KiB)
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 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@01ba3472d1c3 local]# vim a.txt
[root@01ba3472d1c3 local]# cat a.txt
hello
4 列出镜像的变更历史
docker history [镜像名]
[root@01ba3472d1c3 local]# docker history 77c006bf4b15
bash: docker: command not found
[root@01ba3472d1c3 local]# exit
exit
root@zhanghl:/opt/docker/mydocker# docker history 77c006bf4b15
IMAGE CREATED CREATED BY SIZE COMMENT
77c006bf4b15 7 minutes ago /bin/sh -c #(nop) CMD ["/bin/sh">
CMD / ENTRYPOINT 镜像案例
都是指定一个容器启动时要运行的命令
CMD
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
案例 tomcat 的讲解演示
追加 ls -l 命令后 替代了原理运行tomcat的命令，导致docker没有启动
ENTRYPOINT
docker run 之后的参数会被当做参数传递给 ENTRYPOINT，之后形成新的命令组合
案例
制作CMD版可以查询IP信息的容器
DockerFile: Dockerfile -myid
FROM centos
RUN yum install -y curl
CMD ["curl","www.trackip.net/ip?json"]
root@zhanghl:/opt/docker/mydocker# docker build -f Dockerfile-myid -t myid:1.1 .
Sending build context to Docker daemon 3.072kB
Step 1/3 : FROM centos
---> 300e315adb2f
Step 2/3 : RUN yum install -y curl
---> Using cache
---> 82abeb79293f
Step 3/3 : CMD ["curl","www.trackip.net/ip?json"]
---> Running in bafa2c73ec55
Removing intermediate container bafa2c73ec55
---> a566bc415a96
Successfully built a566bc415a96
Successfully tagged myid:1.1
root@zhanghl:/opt/docker/mydocker# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
myid 1.1 a566bc415a96 5 seconds ago 243MB
myip latest 251ed5335c1a 30 minutes ago 243MB
zhl/centos1.1 latest 77c006bf4b15 3 hours ago 291MB
zhl/centos latest e4998e64dece 40 hours ago 209MB
zhl/mytomcat 1.1 a636ea3caaed 4 days ago 672MB
mongo latest 995ccc33e58f 8 days ago 449MB
tomcat latest c0e850d7b9bb 9 days ago 667MB
hello-world latest d1165f221234 8 weeks ago 13.3kB
centos latest 300e315adb2f 4 months ago 209MB
root@zhanghl:/opt/docker/mydocker# docker run -it myid:1.1
{"IP":"175.161.93.164","Country":"CN","UA":"curl\/7.61.1","Time":1619934102}问题,运行时 加参数 -i 报错
root@zhanghl:/opt/docker/mydocker# docker run -it myid:1.1 -i
docker: Error response from daemon: OCI runtime create failed: container_linux.go:367: starting container process caused: exec: "-i": executable file not found in $PATH: unknown.
WHY
我们可以看到可执行文件找不到的报错，executable file not found。
之前我们说过，跟在镜像名后面的是 command，运行时会替换 CMD 的默认值。
因此这里的 -i 替换了原来的 CMD，而不是添加在原来的 curl -s http://ip.cn 后面。而 -i 根本不是命令，所以自然找不到。
那么如果我们希望加入 -i 这参数，我们就必须重新完整的输入这个命令：
$ docker run myip curl -s http://ip.cn -i
制作ENTRYPOINT版查询IP信息的容器
DockerFile:
FROM centos
RUN yum install -y curl
ENTRYPOINT ["curl","www.trackip.net/ip?json"]
build
root@zhanghl:/opt/docker/mydocker# docker build -f Dockerfile-Entrypoint-myip -t myip:1.2 .
Sending build context to Docker daemon 4.096kB
Step 1/3 : FROM centos
---> 300e315adb2f
Step 2/3 : RUN yum install -y curl
---> Using cache
---> 82abeb79293f
Step 3/3 : ENTRYPOINT ["curl","www.trackip.net/ip?json"]
---> Running in 70070b1d358c
Removing intermediate container 70070b1d358c
---> f1f60b285381
Successfully built f1f60b285381
Successfully tagged myip:1.2
root@zhanghl:/opt/docker/mydocker#
运行
root@zhanghl:/opt/docker/mydocker# docker run -it myip:1.2
{"IP":"175.161.93.164","Country":"CN","UA":"curl\/7.61.1","Time":1619934632}root@zhanghl:/opt/docker/mydocker#
root@zhanghl:/opt/docker/mydocker# docker run -it myip:1.2 -i
HTTP/1.1 200 OK
Date: Sun, 02 May 2021 05:50:38 GMT
Content-Type: text/plain
Content-Length: 76
Connection: keep-alive
Set-Cookie: __cfduid=d6e71854852b8ade1b5e9d1ba03386d6a1619934638; expires=Tue, 01-Jun-21 05:50:38 GMT; path=/; domain=.trackip.net; HttpOnly; SameSite=Lax
CF-Cache-Status: DYNAMIC
cf-request-id: 09cd3a08d100000530688e1000000001
Report-To: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report?s=aZpOakyvJEJIy5RKJSanPc6kAxlXG390nfy3ADvHSEbFkG7pzavegW8Xwt7RiF%2F6ExbnXvvp9ZiGHKJ0gD%2F%2F6fm5IyWGJPv%2FeKG1mY%2FGnWQ%3D"}]}
NEL: {"report_to":"cf-nel","max_age":604800}
Server: cloudflare
CF-RAY: 648ef9214d210530-LAX
alt-svc: h4-27=":443"; ma=86400, h4-28=":443"; ma=86400, h4-29=":443"; ma=86400
{"IP":"175.161.93.164","Country":"CN","UA":"curl\/7.61.1","Time":1619934639}root@zhanghl:/opt/docker/mydocker#
root@zhanghl:/opt/docker/mydocker#ONBUILD 命令案例
修改上一步的DockerFile
FROM centos
RUN yum install -y curl
ENTRYPOINT ["curl","www.trackip.net/ip?json"]
ONBUILD RUN echo "father images onbuild------886"
build镜像
docker build -f Dockerfile-Entrypoint-myip -t myip_father .
root@zhanghl:/opt/docker/mydocker# docker build -f Dockerfile-Entrypoint-myip -t myip_father .
Sending build context to Docker daemon 5.12kB
Step 1/4 : FROM centos
---> 300e315adb2f
Step 2/4 : RUN yum install -y curl
---> Using cache
---> 82abeb79293f
Step 3/4 : ENTRYPOINT ["curl","www.trackip.net/ip?json"]
---> Using cache
---> f1f60b285381
Step 4/4 : ONBUILD RUN echo "father images onbuild------886"
---> Using cache
---> 1d20c7ac1ee1
Successfully built 1d20c7ac1ee1
Successfully tagged myip_father:latest
显示信息：
Step 4/4 : ONBUILD RUN echo "father images onbuild------886"
以myip:1.3 为父镜像 编写子镜像DockerFile。Dockerfile-Entrypoint-myip-sub
FROM myip_father
RUN yum install -y curl
ENTRYPOINT ["curl","www.trackip.net/ip?json"]
ONBUILD RUN echo "father images onbuild------886"
~
docker build -f Dockerfile-Entrypoint-myip-sub -t myip_son .
Sending build context to Docker daemon 5.12kB
Step 1/4 : FROM myip_father
# Executing 1 build trigger
---> Running in 9b6bfe884ccd
father images onbuild------886
Removing intermediate container 9b6bfe884ccd
---> d45eda2663bc
Step 2/4 : RUN yum install -y curl
---> Running in 3f4e383eec45
Last metadata expiration check: 1:08:58 ago on Sun May 2 05:10:51 2021.
Package curl-7.61.1-14.el8_3.1.x86_64 is already installed.
Dependencies resolved.
Nothing to do.
Complete!
Removing intermediate container 3f4e383eec45
---> 4cdefe20ba39
Step 3/4 : ENTRYPOINT ["curl","www.trackip.net/ip?json"]
---> Running in 395df3226201
Removing intermediate container 395df3226201
---> fc869c497482
Step 4/4 : ONBUILD RUN echo "father images onbuild------886"
---> Running in 36d3ac20d0fe
Removing intermediate container 36d3ac20d0fe
---> c3615df75130
Successfully built c3615df75130
Successfully tagged myip_son:latest
build时父类onbuild事件被触发
ONBUILD RUN echo "father images onbuild------886"
自定义镜像TOMCAT
1 创建实验目录 /opt/docker/mydocker/tomcat9
2 创建c.txt
touch c.txt
3 将jdk和tomcat安装的压缩包拷贝进目录
root@zhanghl:/opt/docker/mydocker/tomcat9# ll
总用量 152772
drwxr-xr-x 2 root root 4096 5月 2 16:33 ./
drwxr-xr-x 3 root root 4096 5月 2 14:25 ../
-rw-r--r-- 1 root root 11486964 5月 2 14:30 apache-tomcat-9.0.45.tar.gz
-rw-r--r-- 1 root root 0 5月 2 14:28 c.txt
-rw-r--r-- 1 root root 144935989 5月 2 16:31 jdk-8u291-linux-x64.tar.gz
root@zhanghl:/opt/docker/mydocker/tomcat9# pwd
/opt/docker/mydocker/tomcat9
4 在目录下新建Dockerfile文件
FROM centos
MAINTAINER ZHL<253316343@qq.com>
#把宿主机当前上下文的c.txt拷贝到容器/usr/local/路径下
COPY c.txt /usr/local/cincontainer.txt
#把java与tomcat添加到容器中
ADD jdk-8u291-linux-x64.tar.gz /usr/local/
ADD apache-tomcat-9.0.45.tar.gz /usr/local/
#安装vim编辑器
RUN yum -y install vim
#设置工作访问时候的WORKDIR路径，登录落脚点
ENV MYPATH /usr/local
WORKDIR $MYPATH
#配置java与tomcat环境变量
ENV JAVA_HOME /usr/local/jdk1.8.0_291
ENV CLASSPATH $JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
ENV CATALINA_HOME /usr/local/apache-tomcat-9.0.45
ENV CATALINA_BASE /usr/local/apache-tomcat-9.0.45
ENV PATH $PATH:$JAVA_HOME/bin:$CATALINA_HOME/lib:$CATALINA_HOME/bin
#容器运行时监听的端口
EXPOSE 8080
#启动时运行tomcat
# ENTRYPOINT ["/usr/local/apache-tomcat-9.0.45/bin/startup.sh" ]
# CMD ["/usr/local/apache-tomcat-9.0.45/bin/catalina.sh","run"]
CMD /usr/local/apache-tomcat-9.0.45/bin/startup.sh && tail -F /usr/local/apache-tomcat-9.0.45/bin/logs/catalina.out
5 构建
docker build -f /opt/docker/mydocker/tomcat9/DockerFile -t mytomcat9 .
root@zhanghl:/opt/docker/mydocker/tomcat9# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
mytomcat9 latest 2b12a6a03ea0 2 minutes ago 643MB
6 RUN
docker run -d -p 9080:8080 --name myt9 -v /opt/docker/mydocker/tomcat9/test:/usr/local/apache-tomcat-9.0.45/webapps/test -v /opt/docker/mydocker/tomcat9/tomcat9logs/:/usr/local/apache-tomcat-9.0.45/logs mytomcat9
准备两个目录
root@zhanghl:/opt/docker/mydocker/tomcat9# mkdir test
root@zhanghl:/opt/docker/mydocker/tomcat9# mkdir tomcat9logs
root@zhanghl:/opt/docker/mydocker/tomcat9# ll
总用量 152784
drwxr-xr-x 4 root root 4096 5月 2 17:23 ./
drwxr-xr-x 3 root root 4096 5月 2 14:25 ../
-rw-r--r-- 1 root root 11486964 5月 2 14:30 apache-tomcat-9.0.45.tar.gz
-rw-r--r-- 1 root root 0 5月 2 14:28 c.txt
-rw-r--r-- 1 root root 1039 5月 2 16:40 DockerFile
-rw-r--r-- 1 root root 144935989 5月 2 16:31 jdk-8u291-linux-x64.tar.gz
drwxr-xr-x 2 root root 4096 5月 2 17:23 test/
drwxr-xr-x 2 root root 4096 5月 2 17:23 tomcat9logs/
7 验证
进入容器查看目录内容
root@zhanghl:/opt/docker/mydocker/tomcat9# docker exec 882930ee0ac0 ls -l
total 52
drwxr-xr-x 1 root root 4096 May 2 09:16 apache-tomcat-9.0.45
drwxr-xr-x 2 root root 4096 Nov 3 15:22 bin
-rw-r--r-- 1 root root 0 May 2 06:28 cincontainer.txt
drwxr-xr-x 2 root root 4096 Nov 3 15:22 etc
drwxr-xr-x 2 root root 4096 Nov 3 15:22 games
drwxr-xr-x 2 root root 4096 Nov 3 15:22 include
drwxr-xr-x 8 10143 10143 4096 Apr 7 19:26 jdk1.8.0_291
drwxr-xr-x 2 root root 4096 Nov 3 15:22 lib
drwxr-xr-x 3 root root 4096 Dec 4 17:37 lib64
drwxr-xr-x 2 root root 4096 Nov 3 15:22 libexec
drwxr-xr-x 2 root root 4096 Nov 3 15:22 sbin
drwxr-xr-x 5 root root 4096 Dec 4 17:37 share
drwxr-xr-x 2 root root 4096 Nov 3 15:22 src
8 结合前述的容器卷将测试的web服务test发布
在宿主机中共享文件夹中创建Web服务
root@zhanghl:/opt/docker/mydocker/tomcat9/test# mkdir WEB-INF
root@zhanghl:/opt/docker/mydocker/tomcat9/test# cd WEB-INF/
root@zhanghl:/opt/docker/mydocker/tomcat9/test/WEB-INF# vim web.xml
root@zhanghl:/opt/docker/mydocker/tomcat9/test/WEB-INF# vim a.jsp
创建 WEB-INFO目录，并在其下创建 web.xml
web.xml:
test
在 test目录中创建 a.jsp:
Insert title here
-----------welcome------------
<%="i am in docker tomcat self "%>
<% System.out.println("=============docker tomcat self");%>
重启 容器
docker restart [container id]
root@zhanghl:/opt/docker/mydocker/tomcat9/test/WEB-INF# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
882930ee0ac0 mytomcat9 "/bin/sh -c '/usr/lo…" 17 minutes ago Up 17 minutes 0.0.0.0:9080->8080/tcp, :::9080->8080/tcp myt9
root@zhanghl:/opt/docker/mydocker/tomcat9/test/WEB-INF# docker restart 882930ee0ac0
查看网页
查看日志
root@zhanghl:/opt/docker/mydocker/tomcat9/tomcat9logs# cat catalina.out
小总结
到此，关于“什么是Dockerfile”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注创新互联网站，小编会继续努力为大家带来更多实用的文章！
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