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！
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
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
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是软件的原材料
Docker镜像是软件的交付品
Docker容器则可以认为是软件的运行态。 Dockerfile面向开发，Docker镜像成为交付标准，Docker容器则涉及部署与运维，三者缺一不可，合力充当Docker体系的基石 
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。
基础镜像，当前新镜像是基于哪个镜像的
镜像维护者的姓名和邮箱地址
容器构建时需要运行的命令
当前容器对外暴露出的端口
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
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
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
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
容器数据卷，用于数据保存和持久化工作
指定一个容器启动时要运行的命令
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
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
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#
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<UP,BROADCAST,RUNNING,MULTICAST> 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<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@01ba3472d1c3 local]# vim a.txt [root@01ba3472d1c3 local]# cat a.txt hello
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">
都是指定一个容器启动时要运行的命令
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
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#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"
touch c.txt
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
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
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
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/
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
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:
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5"> <display-name>test</display-name> </web-app>
在 test目录中创建 a.jsp:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
-----------welcome------------
<%="i am in docker tomcat self "%>
<br>
<br>
<% System.out.println("=============docker tomcat self");%>
</body>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
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，请继续关注亿速云网站，小编会继续努力为大家带来更多实用的文章！
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