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背景

Docker文件是用来构建docker镜像的文件，由一系列命令和参数构成。

方法概述

使用三步骤：编写docker文件、构建镜像、运行容器

关键字字母必须大写，后面必须有一个空格，以及至少一个参数。每条指令都会创建一个新的镜像层，并对镜像层进行提交。

dockerfile是docker镜像的原材料，docker容器是运行着的镜像

注意，以下dockerfile中，#后面均为注释，编译时需要去掉所有注释

例子

自定义centos的dockerfile

from centos  # 指定此dockerfile是基于哪个镜像的，至少基于scratch ENV mypath /tmp  # 定义环境变量WORKDIR $mypath  # 定义工作目录RUN yum -y install vim  # 执行命令RUN yum -y install net-toolsEXPOSE 80  # 暴露端口号CMD /bin/bash  # 执行最终命令，也可以使用json字符串的形式，比如CMD ["/bin/bash"]

然后编译，-f指定dockerfile，-t指定新的镜像名，.表示当前路径

$ docker build -f my_centos_dockerfile -t szc_centos .

输出如下

Sending build context to Docker daemon  4.096kBStep 1/7 : from centos---> 470671670cacStep 2/7 : ENV mypath /tmp---> Running in eaa3d946fbb4Removing intermediate container eaa3d946fbb4---> 8157d08e287eStep 3/7 : WORKDIR $mypath---> Running in 682be0d895aeRemoving intermediate container 682be0d895ae---> c014d4c29e27Step 4/7 : RUN yum -y install vim---> Running in f532a2aae2c9CentOS-8 - AppStream                            1.5 MB/s | 6.5 MB     00:04CentOS-8 - Base                                 294 kB/s | 5.0 MB     00:17CentOS-8 - Extras                               2.0 kB/s | 2.1 kB     00:01Dependencies resolved.================================================================================Package             Arch        Version                   Repository      Size================================================================================Installing:vim-enhanced        x86_64      2:8.0.1763-13.el8         AppStream      1.4 MInstalling dependencies:gpm-libs            x86_64      1.20.7-15.el8             AppStream       39 kvim-common          x86_64      2:8.0.1763-13.el8         AppStream      6.3 Mvim-filesystem      noarch      2:8.0.1763-13.el8         AppStream       48 kwhich               x86_64      2.21-10.el8               BaseOS          49 kTransaction Summary================================================================================Install  5 PackagesTotal download size: 7.8 MInstalled size: 31 MDownloading Packages:(1/5): gpm-libs-1.20.7-15.el8.x86_64.rpm        198 kB/s |  39 kB     00:00(2/5): vim-filesystem-8.0.1763-13.el8.noarch.rp 868 kB/s |  48 kB     00:00(3/5): vim-enhanced-8.0.1763-13.el8.x86_64.rpm  970 kB/s | 1.4 MB     00:01(4/5): vim-common-8.0.1763-13.el8.x86_64.rpm    1.7 MB/s | 6.3 MB     00:03(5/5): which-2.21-10.el8.x86_64.rpm             6.5 kB/s |  49 kB     00:07--------------------------------------------------------------------------------Total                                           908 kB/s | 7.8 MB     00:08warning: /var/cache/dnf/AppStream-02e86d1c976ab532/packages/gpm-libs-1.20.7-15.el8.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 8483c65d: NOKEYCentOS-8 - AppStream                            1.6 MB/s | 1.6 kB     00:00Importing GPG key 0x8483C65D:Userid     : "CentOS (CentOS Official Signing Key) 
   
    "Fingerprint: 99DB 70FA E1D7 CE22 7FB6 4882 05B5 55B3 8483 C65DFrom       : /etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficialKey imported successfullyRunning transaction checkTransaction check succeeded.Running transaction testTransaction test succeeded.Running transaction  Preparing        :                                                        1/1  Installing       : which-2.21-10.el8.x86_64                               1/5  Installing       : vim-filesystem-2:8.0.1763-13.el8.noarch                2/5  Installing       : vim-common-2:8.0.1763-13.el8.x86_64                    3/5  Installing       : gpm-libs-1.20.7-15.el8.x86_64                          4/5  Running scriptlet: gpm-libs-1.20.7-15.el8.x86_64                          4/5  Installing       : vim-enhanced-2:8.0.1763-13.el8.x86_64                  5/5  Running scriptlet: vim-enhanced-2:8.0.1763-13.el8.x86_64                  5/5  Running scriptlet: vim-common-2:8.0.1763-13.el8.x86_64                    5/5  Verifying        : gpm-libs-1.20.7-15.el8.x86_64                          1/5  Verifying        : vim-common-2:8.0.1763-13.el8.x86_64                    2/5  Verifying        : vim-enhanced-2:8.0.1763-13.el8.x86_64                  3/5  Verifying        : vim-filesystem-2:8.0.1763-13.el8.noarch                4/5  Verifying        : which-2.21-10.el8.x86_64                               5/5Installed:  vim-enhanced-2:8.0.1763-13.el8.x86_64 gpm-libs-1.20.7-15.el8.x86_64  vim-common-2:8.0.1763-13.el8.x86_64   vim-filesystem-2:8.0.1763-13.el8.noarch  which-2.21-10.el8.x86_64Complete!Removing intermediate container f532a2aae2c9---> e7e3f6dfc31bStep 5/7 : RUN yum -y install net-tools---> Running in 3fdcf50a41b2Last metadata expiration check: 0:00:15 ago on Sun Mar  8 08:33:26 2020.Dependencies resolved.================================================================================Package         Architecture Version                        Repository    Size================================================================================Installing:net-tools       x86_64       2.0-0.51.20160912git.el8       BaseOS       323 kTransaction Summary================================================================================Install  1 PackageTotal download size: 323 kInstalled size: 1.0 MDownloading Packages:net-tools-2.0-0.51.20160912git.el8.x86_64.rpm    83 kB/s | 323 kB     00:03--------------------------------------------------------------------------------Total                                            61 kB/s | 323 kB     00:05Running transaction checkTransaction check succeeded.Running transaction testTransaction test succeeded.Running transaction  Preparing        :                                                        1/1  Installing       : net-tools-2.0-0.51.20160912git.el8.x86_64              1/1  Running scriptlet: net-tools-2.0-0.51.20160912git.el8.x86_64              1/1  Verifying        : net-tools-2.0-0.51.20160912git.el8.x86_64              1/1Installed:  net-tools-2.0-0.51.20160912git.el8.x86_64Complete!Removing intermediate container 3fdcf50a41b2---> 654c150a48f3Step 6/7 : EXPOSE 80---> Running in 7b15e7a16d5dRemoving intermediate container 7b15e7a16d5d---> 86ff656eb4cbStep 7/7 : CMD /bin/bash---> Running in 89d9605dcbecRemoving intermediate container 89d9605dcbec---> 57bd622f6cb2Successfully built 57bd622f6cb2Successfully tagged szc_centos:latestSECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host. All files and directories added to build context will have '-rwxr-xr-x' permissions. It is recommended to double check and reset permissions for sensitive files and directories.
   

构建完成，然后运行此镜像的一个容器

$ docker run -it szc_centos[root@32a8169c4044 tmp]#

会发现默认路径就是我们在dockerfile里指定的工作目录/tmp，并且ifconfig、vim命令是可用的

[root@32a8169c4044 tmp]# ifconfigeth0: 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 14  bytes 1116 (1.0 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 0lo: 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@32a8169c4044 tmp]# vim test.txt[root@32a8169c4044 tmp]#
    
   

我们也可以查看这个镜像的历史

$ docker images                                                                                                         REPOSITORY           TAG                 IMAGE ID            CREATED             SIZEszc_centos           latest              57bd622f6cb2        5 minutes ago       327MB...$ docker history 57bd622f6cb2IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT57bd622f6cb2        6 minutes ago       /bin/sh -c #(nop)  CMD ["/bin/sh" "-c" "/bin…   0B86ff656eb4cb        6 minutes ago       /bin/sh -c #(nop)  EXPOSE 80                    0B654c150a48f3        6 minutes ago       /bin/sh -c yum -y install net-tools             26.5MBe7e3f6dfc31b        6 minutes ago       /bin/sh -c yum -y install vim                   63.2MBc014d4c29e27        6 minutes ago       /bin/sh -c #(nop) WORKDIR /tmp                  0B8157d08e287e        6 minutes ago       /bin/sh -c #(nop)  ENV mypath=/tmp              0B470671670cac        7 weeks ago         /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
   
               7 weeks ago         /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
    
                7 weeks ago         /bin/sh -c #(nop) ADD file:aa54047c80ba30064…   237MB
    
   

CMD与ENDTRYPOINT

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

$ docker run -it -p 7777:8080 tomcat ls -ltotal 156-rw-r--r-- 1 root root 19318 Feb  5 22:30 BUILDING.txt-rw-r--r-- 1 root root  5408 Feb  5 22:30 CONTRIBUTING.md-rw-r--r-- 1 root root 57011 Feb  5 22:30 LICENSE-rw-r--r-- 1 root root  1726 Feb  5 22:30 NOTICE-rw-r--r-- 1 root root  3255 Feb  5 22:30 README.md-rw-r--r-- 1 root root  7136 Feb  5 22:30 RELEASE-NOTES-rw-r--r-- 1 root root 16262 Feb  5 22:30 RUNNING.txtdrwxr-xr-x 2 root root  4096 Feb 27 07:56 bindrwxr-xr-x 2 root root  4096 Feb  5 22:30 confdrwxr-xr-x 2 root root  4096 Feb 27 07:56 includedrwxr-xr-x 2 root root  4096 Feb 27 07:56 libdrwxrwxrwx 2 root root  4096 Feb  5 22:26 logsdrwxr-xr-x 3 root root  4096 Feb 27 07:56 native-jni-libdrwxrwxrwx 2 root root  4096 Feb 27 07:56 tempdrwxr-xr-x 2 root root  4096 Feb 27 07:56 webappsdrwxr-xr-x 7 root root  4096 Feb  5 22:28 webapps.distdrwxrwxrwx 2 root root  4096 Feb  5 22:26 work

所以上面的命令根本没有启动tomcat，只是列出了tomcat根目录下的文件

ENTRYPOINT:docker run之后的参数会被传递给ENTRYPOINT指令，形成新的指令组合

例如，以下是用ENTRYPOINT访问http://ip.cn的dockerfile

FROM centosRUN yum install -y curlENTRYPOINT ["curl", "-s", "http://ip.cn"]

而后编译

$ docker build -f myip_docker  -t myip .Sending build context to Docker daemon  6.144kBStep 1/3 : FROM centos---> 470671670cacStep 2/3 : RUN yum install -y curl---> Running in 1b3f6d832cfcCentOS-8 - AppStream                            807 kB/s | 6.5 MB     00:08CentOS-8 - Base                                 161 kB/s | 5.0 MB     00:31CentOS-8 - Extras                               734  B/s | 2.1 kB     00:02Last metadata expiration check: 0:00:01 ago on Sun Mar  8 09:00:19 2020.Package curl-7.61.1-11.el8.x86_64 is already installed.Dependencies resolved.Nothing to do.Complete!Removing intermediate container 1b3f6d832cfc---> e1fe1b0a21a5Step 3/3 : ENTRYPOINT ["curl", "-s", "http://ip.cn"]---> Running in b6dbd548d2f0Removing intermediate container b6dbd548d2f0---> d144c16678cdSuccessfully built d144c16678cdSuccessfully tagged myip:latestSECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host. All files and directories added to build context will have '-rwxr-xr-x' permissions. It is recommended to double check and reset permissions for sensitive files and directories.

运行myip容器时可以加上新的选项，来传给dockerfile里的curl命令

$ docker run -it myip -iHTTP/1.1 403 ForbiddenDate: Sun, 08 Mar 2020 09:01:12 GMTContent-Type: text/plain; charset=UTF-8Transfer-Encoding: chunkedConnection: keep-aliveSet-Cookie: __cfduid=d1143a1df005fa16e02870ec8c10c51811583658072; expires=Tue, 07-Apr-20 09:01:12 GMT; path=/; domain=.ip.cn; HttpOnly; SameSite=Lax; SecureCache-Control: max-age=15Expires: Sun, 08 Mar 2020 09:01:27 GMTAlt-Svc: h3-27=":443"; ma=86400, h3-25=":443"; ma=86400, h3-24=":443"; ma=86400, h3-23=":443"; ma=86400Server: cloudflareCF-RAY: 570b5ec859dfd93a-HKGerror code: 1020

ONBUILD案例

ONBUILD关键字用来指定当此dockerfile被引用时执行的命令。

以下是案例：先构建myip_docker

FROM centosRUN yum install -y curlENTRYPOINT ["curl", "-s", "https://www.uestc.edu.cn/"]ONBUILD RUN echo "Father image onbuild finished.."

然后构建镜像

$ docker build -f myip_docker  -t myip .

再编写mydocker_son，引用镜像myip

FROM myipRUN yum install -y curlCMD ["curl", "-s", "http://www.baidu.com"]

使用此文件构建镜像时，myip的dockerfile中的ONBUILD语句就会执行

$ docker build -f myip_son  -t myip_son ....Father image onbuild finished.....Successfully built 770b567e828fSuccessfully tagged myip_son:latest...

自定义tomcat

dockerfile内容如下，编译此文件需要其所在目录下有c.txt、jdk-8u171-linux-x64.tar.gz和apache-tomcat-9.0.8.tar.gz三个文件

FROM centosMAINTAINER songzecengCOPY c.txt /usr/local/c_s.txt  # 把文件复制到镜像指定文件中ADD jdk-8u171-linux-x64.tar.gz /usr/local/  # 把压缩包解压后复制到镜像指定目录中ADD apache-tomcat-9.0.8.tar.gz /usr/local/RUN yum -y install vimENV MYPATH /usr/localWORKDIR $MYPATHENV JAVA_HOME /usr/local/jdk1.8.0_171ENV CLASSPATH $JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jarENV CATALINA_HOME /usr/local/apache-tomcat-9.0.8ENV CATALINA_BASE /usr/local/apache-tomcat-9.0.8ENV PATH $PATH:$JAVA_HOME/bin:$CATALINA_HOME/lib:$CATALINA_HOME/binEXPOSE 8080CMD $CATALINA_HOME/bin/startup.sh && tail -F $CATALINA_HOME/bin/logs/logs.txt  # 输出日志

而后编译

$ docker build -f my_tomcat_docker -t szc_tomcat .

最后运行

$ docker run -d -p 9080:8080 --name szc_tomcat_00 -v /c/Users/songzeceng/tomcat/out:/usr/local/apache-tomcat-9.0.8/webapps/test -v /c/Users/songzeceng.tomcat/logs:/usr/local/apache-tomcat-9.0.8/logs --privileged=true szc_tomcat

-d表示后台运行容器，然后指定端口映射、容器名字，以及两个数据卷，最后--privileged=true确保容器可写

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