一、Dockerfile的条条框框
1、什么是Dockerfile？
Dockerfile是一种被Docker程序解释的脚本。Dockerfile由一条一条的指令组成，并且有自己的书写格式和支持的命令。当我们需要指定自己额外的需求时，只需在Dockerfile上添加或修改指令，然后通过docker build生成我们自定义的镜像（image）。
2、Dockerfile的注意事项
- Dockerfile的指令是忽略大小写的，建议使用大写
- 每一行只支持一条指令
- 每条指令可以携带多个参数
- 支持以#开头的注释
3、Dockerfile指令（instruction）
构建指令：用于构建image。其指定的操作不会在运行image的容器上执行（FROM、MAINTAINER、RUN、ENV、ADD、COPY）
设置指令：用于设置image的属性。其指定的操作将在运行image的容器中执行（CMD、ENTRYPOINT、USER 、EXPOSE、VOLUME、WORKDIR、ONBUILD）
4、Dockerfile的基本结构
基础镜像信息、维护者信息、镜像操作指令、容器启动时执行指令
二、Dockerfile指令（instruction）实操
1、FROM（指定基础image，必须为第一个命令）
格式：
FROM <image> FROM <image>:<tag>
例：
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest [root@localhost docker]# docker build -t my_test . #注意有个“.” Sending build context to Docker daemon 2.048kB Step 1/1 : FROM centos:latest ---> 9f38484d220f Successfully built 9f38484d220f Successfully tagged my_test:latest
2、MAINTAINER（维护者，用来指定创建者信息）
格式：
MAINTAINER <name>
例：（通过inspect验证）
[root@localhost docker]# vim Dockerfile
#FROM centos
FROM centos:latest
MAINTAINER Xuyun Liu <1972163777@qq.com>
[root@localhost docker]# docker build -t my_test .
Sending build context to Docker daemon 2.048kB
Step 1/2 : FROM centos:latest
---> 9f38484d220f
Step 2/2 : MAINTAINER Xuyun Liu <1972163777@qq.com>
---> Using cache
---> be97dff9636f
Successfully built be97dff9636f
Successfully tagged my_test:latest
[root@localhost docker]# docker inspect -f {{.Author}} my_test
Xuyun Liu <1972163777@qq.com>
3、RUN（安装软件用）
格式：
RUN command param1 param2 #使用shell终端运行命令（/bin/sh、/bin/bash等） RUN ['executable(可执行的))','param1（参数）','param2'...] #不通过shell执行，而是通过内建命令exec去执行
例：
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest MAINTAINER Xuyun Liu <1972163777@qq.com> RUN touch /home/a.txt RUN ["touch","/home/b.txt"] #这里双引号和单引号也是有讲究的，单引号会报错 [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/4 : FROM centos:latest ---> 9f38484d220f Step 2/4 : MAINTAINER Xuyun Liu <1972163777@qq.com> ---> Using cache ---> be97dff9636f Step 3/4 : RUN touch /home/a.txt ---> Using cache ---> 5af84bebdda1 Step 4/4 : RUN ["touch","/home/b.txt"] ---> Running in 541b7c7da76a Removing intermediate container 541b7c7da76a ---> 6e19811bbf18 Successfully built 6e19811bbf18 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test ls /home a.txt b.txt
4、CMD（设置container启动时执行的操作）
格式：
CMD command param1 param2 CMD ["executable","param1","param2"...] CMD ["param1","param2"...] #当CMD和ENTRYPOINT配合使用时的写法
例1：CMD指令会被docker run提供的参数覆盖
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] CMD ls /dev [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/3 : FROM centos:latest ---> 9f38484d220f Step 2/3 : RUN touch /home/a.txt ---> Running in 384f2554526a Removing intermediate container 384f2554526a ---> cfb30d89ad46 Step 3/3 : CMD ls /dev ---> Running in b568167236d3 Removing intermediate container b568167236d3 ---> 1e1971815006 Successfully built 1e1971815006 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test console fd mqueue ptmx random stderr stdout urandom core full null pts shm stdin tty zero [root@localhost docker]# docker run -it my_test ls /home a.txt
例2：当一个Dockfile文件中有两个或多个CMD指令时，只执行最后一条CMD指令
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] CMD ls /dev CMD ["ls","/usr","/usr/local"] [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/4 : FROM centos:latest ---> 9f38484d220f Step 2/4 : RUN touch /home/a.txt ---> Using cache ---> cfb30d89ad46 Step 3/4 : CMD ls /dev ---> Using cache ---> 1e1971815006 Step 4/4 : CMD ["ls","/usr","/usr/local"] ---> Running in ccfabb87efc5 ^[[ARemoving intermediate container ccfabb87efc5 ---> e439603840ef Successfully built e439603840ef Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test /usr: bin etc games include lib lib64 libexec local sbin share src tmp /usr/local: bin etc games include lib lib64 libexec sbin share src
5、ENTRYPOINT（设置container启动时执行的操作）
格式：
ENTRYPOINT command param1 param2 ENTRYPOINT ["executable","param1","param2"]
例1：ENTRYPOINT指令不会被docker run提供的参数覆盖
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] #CMD ls /dev #CMD ["ls","/usr","/usr/local"] ENTRYPOINT ls /root /sys [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/3 : FROM centos:latest ---> 9f38484d220f Step 2/3 : RUN touch /home/a.txt ---> Using cache ---> cfb30d89ad46 Step 3/3 : ENTRYPOINT ls /root /sys ---> Running in 67be0ac881cb Removing intermediate container 67be0ac881cb ---> e51f45c181ac Successfully built e51f45c181ac Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test /root: anaconda-ks.cfg /sys: block class devices fs kernel power bus dev firmware hypervisor module [root@localhost docker]# docker run -it my_test ls /home /root: anaconda-ks.cfg /sys: block class devices fs kernel power bus dev firmware hypervisor module
例2：当一个Dockerfile文件中有两个或多个ENTRYPOINT指令时，只执行最后一条ENTRYPOINT指令
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] #CMD ls /dev #CMD ["ls","/usr","/usr/local"] ENTRYPOINT ls /root /sys ENTRYPOINT ["ls","/home"] [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/4 : FROM centos:latest ---> 9f38484d220f Step 2/4 : RUN touch /home/a.txt ---> Using cache ---> cfb30d89ad46 Step 3/4 : ENTRYPOINT ls /root /sys ---> Using cache ---> e51f45c181ac Step 4/4 : ENTRYPOINT ["ls","/home"] ---> Running in 95c2491f9b3b Removing intermediate container 95c2491f9b3b ---> 6196eaff66d3 Successfully built 6196eaff66d3 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test a.txt
例3：当一个Dockerfile文件中既有CMD指令又有ENTRYPOINT指令时，CMD指令将被作为ENTRYPOINT指令的参数
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] #CMD ls /dev #CMD ["ls","/usr","/usr/local"] #ENTRYPOINT ls /root /sys CMD ["-l"] ENTRYPOINT ["ls","/home"] [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/4 : FROM centos:latest ---> 9f38484d220f Step 2/4 : RUN touch /home/a.txt ---> Using cache ---> cfb30d89ad46 Step 3/4 : CMD ["-l"] ---> Using cache ---> 4c5cf79c279d Step 4/4 : ENTRYPOINT ["ls","/home"] ---> Using cache ---> 14d643d73d81 Successfully built 14d643d73d81 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test total 0 -rw-r--r-- 1 root root 0 Aug 29 17:09 a.txt
6、USER（设置container的用户，默认是root用户，这个root不是那个root）
格式：
USER username/uid
例：
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> #RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] #CMD ls /dev #CMD ["ls","/usr","/usr/local"] #ENTRYPOINT ls /root /sys #CMD ["-l"] #ENTRYPOINT ["ls","/home"] RUN useradd admin #需要先创建一个用户，不然会提示用户不存在 USER admin [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/3 : FROM centos:latest ---> 9f38484d220f Step 2/3 : RUN useradd admin ---> Running in a4847a39ab06 Removing intermediate container a4847a39ab06 ---> 3759bdc0589c Step 3/3 : USER admin ---> Running in 80e367ffe699 Removing intermediate container 80e367ffe699 ---> c95196915358 Successfully built c95196915358 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test /bin/bash [admin@f0f565e8da5a /]$
7、EXPOSE（暴露，指定容器需要映射到宿主机的端口）
格式：
EXPOSE port1 [port2 ...]
例：
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> #RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] #CMD ls /dev #CMD ["ls","/usr","/usr/local"] #ENTRYPOINT ls /root /sys #CMD ["-l"] #ENTRYPOINT ["ls","/home"] #RUN useradd admin #USER admin EXPOSE 80 [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/2 : FROM centos:latest ---> 9f38484d220f Step 2/2 : EXPOSE 80 ---> Running in 75dda1ff5393 Removing intermediate container 75dda1ff5393 ---> f6759e9df32d Successfully built f6759e9df32d Successfully tagged my_test:latest [root@localhost docker]# docker run -dit -p 80 my_test /bin/bash #随机映射 5b790387fd758115204ce0a1f7ed1daa17a983108004948cb26b81f8fa8dc1f6 #随机映射（大P） [root@localhost docker]# docker run -dit -P my_test /bin/bash #映射到宿主机的80 7207f9ae8a2c2932df727854cecb6b16d6b09ffecd1411bf42d03ffb1c271803 [root@localhost docker]# docker run -dit -p 80:80 my_test /bin/bash 83c40826648c13d23c706db3474d1eb541261638e5c1415abaebfb7a37d758ca [root@localhost docker]# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 83c40826648c my_test "/bin/bash" About a minute ago Up About a minute 0.0.0.0:80->80/tcp silly_snyder 7207f9ae8a2c my_test "/bin/bash" 2 minutes ago Up 2 minutes 0.0.0.0:32769->80/tcp youthful_kirch 5b790387fd75 my_test "/bin/bash" 2 minutes ago Up 2 minutes 0.0.0.0:32768->80/tcp focused_bose
8、ENV（用于设置环境变量）
格式：
ENV <key> <value>
例：
[root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> #RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] #CMD ls /dev #CMD ["ls","/usr","/usr/local"] #ENTRYPOINT ls /root /sys #CMD ["-l"] #ENTRYPOINT ["ls","/home"] #RUN useradd admin #USER admin #EXPOSE 80 ENV a Hello World!! [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 2.048kB Step 1/2 : FROM centos:latest ---> 9f38484d220f Step 2/2 : ENV a Hello World!! ---> Running in af33c5e13754 Removing intermediate container af33c5e13754 ---> dd22ab298385 Successfully built dd22ab298385 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test /bin/bash [root@7dca23648303 /]# echo $a Hello World!!
9、ADD（将源文件复制到container的目标文件）
格式：
ADD <src> <dest>
注：src可以是Dockerfile所在目录的相对路径，也可以是一个绝对路径；
src为tar文件时，自动减压到dest中；
src为一个web的url时，会自动下载到dest中；
写dest路径时注意结尾的“/”，结尾有“/”和没“/”是有区别的
例：
[root@localhost docker]# pwd /root/docker [root@localhost docker]# echo "Hello World!!" > test.txt [root@localhost docker]# wget http://Nginx.org/download/nginx-1.16.1.tar.gz [root@localhost docker]# ls Dockerfile nginx-1.16.1.tar.gz test.txt [root@localhost docker]# vim Dockerfile #FROM centos FROM centos:latest #MAINTAINER Xuyun Liu <1972163777@qq.com> #RUN touch /home/a.txt #RUN ["touch","/home/b.txt"] #CMD ls /dev #CMD ["ls","/usr","/usr/local"] #ENTRYPOINT ls /root /sys #CMD ["-l"] #ENTRYPOINT ["ls","/home"] #RUN useradd admin #USER admin #EXPOSE 80 #ENV a Hello World!! ADD test.txt /tmp ADD nginx-1.16.1.tar.gz /tmp ADD http://nginx.org/download/nginx-1.16.1.tar.gz /home [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 1.036MB Step 1/4 : FROM centos:latest ---> 9f38484d220f Step 2/4 : ADD test.txt /tmp ---> 7fa385db5eef Step 3/4 : ADD nginx-1.16.1.tar.gz /tmp ---> 24c9c0e0877d Step 4/4 : ADD http://nginx.org/download/nginx-1.16.1.tar.gz /home Downloading 1.033MB/1.033MB ---> b842677c7912 Successfully built b842677c7912 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test ls /tmp /home /home: nginx-1.16.1.tar.gz /tmp: ks-script-eC059Y nginx-1.16.1 test.txt yum.log #ks-script-eC059Y和yum.log是原有文件
10、COPY（复制本地主机的<src>到容器中的<dest>，与ADD指令相似）
格式：
COPY <src> <dest>
注：COPY指令和ADD指令功能和使用方式类似，但COPY指令只是复制，不会下载和解压
例：
[root@localhost docker]# echo "This is a test." > test.html [root@localhost docker]# ls Dockerfile nginx-1.16.1.tar.gz test.html test.txt [root@localhost docker]# vim Dockerfile FROM centos:latest COPY test.html / [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 1.037MB Step 1/2 : FROM centos:latest ---> 9f38484d220f Step 2/2 : COPY test.html / ---> e48a7c46ded6 Successfully built e48a7c46ded6 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test ls -l /test.html -rw-r--r-- 1 root root 16 Aug 29 18:30 /test.html
11、VOLUME（卷，指定挂载点）
格式：
VOLUME ["<mountpoint>"]
12、WORKDIR（切换目录，可以多次切换，相当于cd命令）
格式：
WORKDIR Directory_url
例：
[root@localhost docker]# vim Dockerfile FROM centos:latest WORKDIR /tmp RUN mkdir test WORKDIR test RUN ["touch","a.txt","b.txt"] [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 1.037MB Step 1/5 : FROM centos:latest ---> 9f38484d220f Step 2/5 : WORKDIR /tmp Removing intermediate container 9258f95093db ---> 6b8f6f6c69f6 Step 3/5 : RUN mkdir test ---> Running in e44f8d897714 Removing intermediate container e44f8d897714 ---> 1dc77dd96431 Step 4/5 : WORKDIR test Removing intermediate container df09ed12198d ---> 94cb324c6118 Step 5/5 : RUN ["touch","a.txt","b.txt"] ---> Running in 63f6bdcdd475 Removing intermediate container 63f6bdcdd475 ---> 1ae6996b6573 Successfully built 1ae6996b6573 Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test ls -l /tmp/test total 0 -rw-r--r-- 1 root root 0 Aug 29 18:39 a.txt -rw-r--r-- 1 root root 0 Aug 29 18:39 b.txt
13、ONBUILD（在子镜像中执行）
格式：
ONBUILD INSTRUCTION
例：
[root@localhost docker]# vim Dockerfile [root@localhost docker]# docker build -t my_test . Sending build context to Docker daemon 1.038MB Step 1/2 : FROM centos:latest ---> 9f38484d220f Step 2/2 : ONBUILD RUN touch /home/abc.txt ---> Running in b7f920c860a3 Removing intermediate container b7f920c860a3 ---> 991234fb1d8e Successfully built 991234fb1d8e Successfully tagged my_test:latest [root@localhost docker]# docker run -it my_test ls -l /home total 0 #并没有创建abc.txt文件 [root@localhost docker]# mkdir test #需要再创建一个子Dockerfile文件，所以创建一个test目录来存放子Dockerfile文件，和父镜像的Dockerfile隔离开来 [root@localhost docker]# cd test [root@localhost test]# pwd /root/docker/test [root@localhost test]# vim Dockerfile FROM my_test:latest #写父镜像 [root@localhost test]# docker build -t mytest2 . Sending build context to Docker daemon 2.048kB Step 1/1 : FROM my_test:latest # Executing 1 build trigger ---> Running in b035d0948b03 Removing intermediate container b035d0948b03 ---> 21e0f69c2eed Successfully built 21e0f69c2eed Successfully tagged mytest2:latest [root@localhost test]# docker run -it mytest2 ls -l /home total 0 -rw-r--r-- 1 root root 0 Aug 29 18:58 abc.txt #此时会创建abc.txt文件
最后用两张张图解释常用指令的意义（有一说一图是从网上ba的，可能有点模糊不知道你们能不能看清，概括的挺好）
