在之前Docker的使用中，我们直接从仓库下载需要的镜像到本地，然后稍加配置就可以应用了，通常从仓库下载下来的镜像都是通用的，无任何私有化的东西，我们拿过来就需要加很多的配置，每次使用就很麻烦。如果我们想定制化某一个镜像可以吗？比如Nginx，我不想每次使用都加很多的配置，而是定制化后，我再按照定制化的规则去使用，及时的安装部署我需要的Nginx环境。DockerFile就是做这个工作的，一个用基础镜像来构建新镜像的文本文件，里面包含构建镜像需要的各种指令。 在之前Docker的使用中，我们直接从仓库下载需要的镜像到本地，然后稍加配置就可以应用了，通常从仓库下载下来的镜像都是通用的，无任何私有化的东西，我们拿过来就需要加很多的配置，每次使用就很麻烦。如果我们想定制化某一个镜像可以吗？比如Nginx，我不想每次使用都加很多的配置，而是定制化后，我再按照定制化的规则去使用，及时的安装部署我需要的Nginx环境。DockerFile就是做这个工作的，一个用基础镜像来构建新镜像的文本文件，里面包含构建镜像需要的各种指令。
使用Dockerfile构建Nginx镜像，在一个空目录下创建Dockerfile文件
[root@hadoop101 nginx]# pwd/home/docker_test/docker_files/nginx[root@hadoop101 nginx]# vim Dockerfile[root@hadoop101 nginx]# lltotal 4-rw-r--r-- 1 root root 153 Mar 29 23:33 DockerfileDockerfile内容如下：
FROM nginx?VOLUME ["volume01","volume02"]?RUN echo 'welcome,this is a nginx image of build local.' > /usr/share/nginx/html/index.html?RUN echo '----end----'?RUN /bin/bash[root@hadoop101 nginx]# docker build -t zhangbao/nginx001:1.0 .
[root@hadoop101 nginx]# docker build -t zhangbao/nginx001:1.0 .Sending build context to Docker daemon 2.048kBStep 1/5 : FROM nginx ---> 605c77e624ddStep 2/5 : VOLUME ["volume01","volume02"] ---> Running in d9ff85f068bfRemoving intermediate container d9ff85f068bf ---> 801484ddbb09Step 3/5 : RUN echo '构建本地nginx镜像' > /usr/share/nginx/html/index.html ---> Running in 6614ebace633Removing intermediate container 6614ebace633 ---> 29a385ed17b6Step 4/5 : RUN echo '----end----' ---> Running in 3449cc6cf814----end----Removing intermediate container 3449cc6cf814 ---> 5d6941c830a4Step 5/5 : RUN /bin/bash ---> Running in 1f106444b093Removing intermediate container 1f106444b093 ---> 440fd4b943c7Successfully built 440fd4b943c7Successfully tagged zhangbao/nginx001:1.0[root@hadoop101 nginx]#docker run -d -p 80:80 zhangbao/nginx001:1.0
访问：http://192.168.88.71/
首页可以查看 welcome,this is a nginx image of build local.
构建一个新镜像，我们可以大致分为三个步骤：编写Dockerfile文件 > docker build > docker run
Dockerfile的基础知识
每个关键字（指令）都必须大写
执行过程从上到下，顺序执行
#为注释
每个指令代表一层，都会创建提交一个新的镜像层
Dockerfile指令
FROM 指定基础镜像MAINTAINER 指定作者RUN 执行参数中定义的命令，构建镜像时需要的命令EXPOSE 向容器外部公开的端口号WORKDIR 设置容器内默认工作目录USER 指定用户ENTROYPOINT 指定一个容器启动时运行的命令ENV 设置环境变量ADD|COPY 复制文件到镜像中VOLUME 容器数据卷，向镜像创建的容器添加卷CMD 容器启动时要运行的命令，可以有多个，但只有最后一个生效Dockerfile的构建过程就是build的执行过程
1.把当前目录和子目录当做上下文传递给docker服务，命令最后的点表示当前上下文。2.从当前目录（不包括子目录）找到Dockerfile文件，如果不指定文件，必须是此文件名。3.检查docker语法。4.从基础镜像运行一个容器。5.执行指令，修改容器，如上面操作添加数据卷，修改首页。6.对修改后的容器提交一个新的镜像层，也可叫做中间层镜像。7.针对中间层生成的镜像，运行新的容器。8.重复执行修改容器、提交镜像、运行容器指令，直到所有指令执行完成。注：每条指令都会生成新的镜像，也就是生成中间层镜像，这样执行速度其实会很慢，可以不使用缓存。在构建命令中加上
--no-cache=true即可。可根据实际场景选择是否需要缓存。
我们已经熟悉了构建Dockerfile的基础指令，现在可以做一些基本实践了。
首先我们运行一个原生的centos，然后做一些linux的基本操作
[root@hadoop101 ~]# docker run -it centos /bin/bash[root@a0db59573b95 /]# lsbin dev etc home lib lib64 lost+found media mnt opt proc root run sbin srv sys tmp usr var[root@a0db59573b95 /]# llbash: ll: command not found[root@a0db59573b95 /]# vim testbash: vim: command not found[root@a0db59573b95 /]# ifconfigbash: ifconfig: command not found[root@a0db59573b95 /]#可以看到，我们已经运行一个centos，然后发现一些基础的命令是没有的，这就说明这个contos是一个压缩版的，如果我们想运行一个有这些命令的镜像呢？这就需要在Dockerfile中做一些操作了？
记住在一个空白的目录下创建Dockerfile文件，我这里文件名dockerfile-mycentos，内容如下：
FROM centos#指定作者MAINTAINER zhangbao<zhangbaohpu@163.com>?ENV MYPATH /usr/localWORKDIR $MYPATH?#下载需要的工具类RUN yum -y install vimRUN yum -y install net-tools?EXPOSE 80?CMD echo "--end--"CMD /bin/bash如果是自定义Dockerfile文件名，则构建时必须指定文件名，否则文件名必须是：Dockerfile
[root@hadoop101 mycentos]# docker build -f dockerfile-mycentos -t mysentos:1.0 .Sending build context to Docker daemon 2.048kBStep 1/9 : FROM centos ---> 5d0da3dc9764Step 2/9 : MAINTAINER zhangbao<zhangbaohpu@163.com> ---> Running in d9b4afe40ef6Removing intermediate container d9b4afe40ef6 ---> 87e522a4dcb6Step 3/9 : ENV MYPATH /usr/local ---> Running in 2fe975209f1eRemoving intermediate container 2fe975209f1e ---> 30491c2e1634Step 4/9 : WORKDIR $MYPATH ---> Running in cd9b1810f244Removing intermediate container cd9b1810f244 ---> d2addbefe4f6Step 5/9 : RUN yum -y install vim ---> Running in d6a8caa012e9CentOS Linux 8 - AppStream 64 B/s | 38 B 00:00Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlistThe command '/bin/sh -c yum -y install vim' returned a non-zero code: 1[root@hadoop101 mycentos]#这时候发现失败了，查问题是centos8的官方源已经下线了，导致yum下载失败。那刚好，我们在自定义镜像的时候可以修复这些问题。只需修改yum的默认源就可以了，这个操作也放在Dockerfile文件内。我们修复后Dockerfile文件如下：
FROM centos#指定作者MAINTAINER zhangbao<zhangbaohpu@163.com>#ENV kv格式，这里指定工作目录，及默认进入容器的目录ENV MYPATH /usr/localWORKDIR $MYPATH#将原有的yum配置备份下RUN tar cvf /etc/yum.repos.d.tar /etc/yum.repos.d#修改yum源配置，RUN curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo#删除掉多于的repo文件RUN rm -rf /etc/yum.repos.d/CentOS-Linux-*#使yum配置更新RUN yum clean allRUN yum makecache#下载需要的工具类RUN yum -y install vimRUN yum -y install net-toolsEXPOSE 80CMD echo "--end--"CMD /bin/bash重新构建下修改后的Dockerfile文件
docker build -f dockerfile-mycentos -t mysentos:1.0 .
[root@hadoop101 mycentos]# docker build -f dockerfile-mycentos -t mysentos:1.0 .Sending build context to Docker daemon 2.56kBStep 1/14 : FROM centos ---> 5d0da3dc9764Step 2/14 : MAINTAINER zhangbao<zhangbaohpu@163.com> ---> Running in 79ff0ddc554dRemoving intermediate container 79ff0ddc554d ---> 0cc1bf4a4ba0Step 3/14 : ENV MYPATH /usr/local ---> Running in 59d3d432c58cRemoving intermediate container 59d3d432c58c ---> 839ed1e4b944Step 4/14 : WORKDIR $MYPATH ---> Running in d085e4887d92Removing intermediate container d085e4887d92 ---> 41c10774900bStep 5/14 : RUN tar cvf /etc/yum.repos.d.tar /etc/yum.repos.d ---> Running in 1ab58ab850c0/etc/yum.repos.d//etc/yum.repos.d/CentOS-Linux-AppStream.repo/etc/yum.repos.d/CentOS-Linux-BaseOS.repo/etc/yum.repos.d/CentOS-Linux-ContinuousRelease.repo/etc/yum.repos.d/CentOS-Linux-Debuginfo.repo/etc/yum.repos.d/CentOS-Linux-Devel.repo/etc/yum.repos.d/CentOS-Linux-Extras.repo/etc/yum.repos.d/CentOS-Linux-FastTrack.repo/etc/yum.repos.d/CentOS-Linux-HighAvailability.repo/etc/yum.repos.d/CentOS-Linux-Media.repo/etc/yum.repos.d/CentOS-Linux-Plus.repo/etc/yum.repos.d/CentOS-Linux-PowerTools.repo/etc/yum.repos.d/CentOS-Linux-Sources.repotar: Removing leading `/' from member namesRemoving intermediate container 1ab58ab850c0 ---> bfd1c4cd694cStep 6/14 : RUN curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo ---> Running in 73ebef623f8a % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed100 2495 100 2495 0 0 12351 0 --:--:-- --:--:-- --:--:-- 12351Removing intermediate container 73ebef623f8a ---> 22812c68f967Step 7/14 : RUN rm -rf /etc/yum.repos.d/CentOS-Linux-* ---> Running in eb8426f499b0Removing intermediate container eb8426f499b0 ---> 8dc6bd0b4e84Step 8/14 : RUN yum clean all ---> Running in a508fb5031580 files removedRemoving intermediate container a508fb503158 ---> c6831cfda20fStep 9/14 : RUN yum makecache ---> Running in 67c3f0dc0a6aCentOS-8.5.2111 - Base - mirrors.aliyun.com 16 MB/s | 4.6 MB 00:00CentOS-8.5.2111 - Extras - mirrors.aliyun.com 45 kB/s | 10 kB 00:00CentOS-8.5.2111 - AppStream - mirrors.aliyun.co 16 MB/s | 8.4 MB 00:00Metadata cache created.Removing intermediate container 67c3f0dc0a6a ---> 6ca3b2fbeb13Step 10/14 : RUN yum -y install vim ---> Running in e81b9f1a4705Last metadata expiration check: 0:00:05 ago on Tue Apr 5 09:35:43 2022.Dependencies resolved.================================================================================ Package Arch Version Repository Size================================================================================Installing: vim-enhanced x86_64 2:8.0.1763-16.el8 AppStream 1.4 MInstalling dependencies: gpm-libs x86_64 1.20.7-17.el8 AppStream 39 k vim-common x86_64 2:8.0.1763-16.el8 AppStream 6.3 M vim-filesystem noarch 2:8.0.1763-16.el8 AppStream 49 k which x86_64 2.21-16.el8 base 49 kTransaction Summary================================================================================Install 5 PackagesTotal download size: 7.8 MInstalled size: 30 MDownloading Packages:(1/5): gpm-libs-1.20.7-17.el8.x86_64.rpm 235 kB/s | 39 kB 00:00(2/5): which-2.21-16.el8.x86_64.rpm 203 kB/s | 49 kB 00:00(3/5): vim-filesystem-8.0.1763-16.el8.noarch.rp 776 kB/s | 49 kB 00:00(4/5): vim-common-8.0.1763-16.el8.x86_64.rpm 16 MB/s | 6.3 MB 00:00(5/5): vim-enhanced-8.0.1763-16.el8.x86_64.rpm 5.4 MB/s | 1.4 MB 00:00--------------------------------------------------------------------------------Total 19 MB/s | 7.8 MB 00:00Running transaction checkTransaction check succeeded.Running transaction testTransaction test succeeded.Running transaction Preparing : 1/1 Installing : vim-filesystem-2:8.0.1763-16.el8.noarch 1/5 Installing : vim-common-2:8.0.1763-16.el8.x86_64 2/5 Installing : gpm-libs-1.20.7-17.el8.x86_64 3/5 Running scriptlet: gpm-libs-1.20.7-17.el8.x86_64 3/5 Installing : which-2.21-16.el8.x86_64 4/5 Installing : vim-enhanced-2:8.0.1763-16.el8.x86_64 5/5 Running scriptlet: vim-enhanced-2:8.0.1763-16.el8.x86_64 5/5 Running scriptlet: vim-common-2:8.0.1763-16.el8.x86_64 5/5 Verifying : which-2.21-16.el8.x86_64 1/5 Verifying : gpm-libs-1.20.7-17.el8.x86_64 2/5 Verifying : vim-common-2:8.0.1763-16.el8.x86_64 3/5 Verifying : vim-enhanced-2:8.0.1763-16.el8.x86_64 4/5 Verifying : vim-filesystem-2:8.0.1763-16.el8.noarch 5/5Installed: gpm-libs-1.20.7-17.el8.x86_64 vim-common-2:8.0.1763-16.el8.x86_64 vim-enhanced-2:8.0.1763-16.el8.x86_64 vim-filesystem-2:8.0.1763-16.el8.noarch which-2.21-16.el8.x86_64Complete!Removing intermediate container e81b9f1a4705 ---> 3d731b0904e6Step 11/14 : RUN yum -y install net-tools ---> Running in f45f6c7c9c8cLast metadata expiration check: 0:00:17 ago on Tue Apr 5 09:35:43 2022.Dependencies resolved.================================================================================ Package Architecture Version Repository Size================================================================================Installing: net-tools x86_64 2.0-0.52.20160912git.el8 base 322 kTransaction Summary================================================================================Install 1 PackageTotal download size: 322 kInstalled size: 942 kDownloading Packages:net-tools-2.0-0.52.20160912git.el8.x86_64.rpm 934 kB/s | 322 kB 00:00--------------------------------------------------------------------------------Total 930 kB/s | 322 kB 00:00Running transaction checkTransaction check succeeded.Running transaction testTransaction test succeeded.Running transaction Preparing : 1/1 Installing : net-tools-2.0-0.52.20160912git.el8.x86_64 1/1 Running scriptlet: net-tools-2.0-0.52.20160912git.el8.x86_64 1/1 Verifying : net-tools-2.0-0.52.20160912git.el8.x86_64 1/1Installed: net-tools-2.0-0.52.20160912git.el8.x86_64Complete!Removing intermediate container f45f6c7c9c8c ---> adc0f183e07eStep 12/14 : EXPOSE 80 ---> Running in 9422041e18c2Removing intermediate container 9422041e18c2 ---> e94ae254891fStep 13/14 : CMD echo "--end--" ---> Running in 9183b6a1444dRemoving intermediate container 9183b6a1444d ---> c3978bb3cb17Step 14/14 : CMD /bin/bash ---> Running in 536c8de964d3Removing intermediate container 536c8de964d3 ---> 68f0ddc7c99fSuccessfully built 68f0ddc7c99fSuccessfully tagged mysentos:1.0[root@hadoop101 mycentos]#总共分为14步，即每个指令一步，也表示每一步算一层。整个构建过程还是很详细的。
自定义镜像已经构建完成，下面我们开始运行镜像，并检测下基础命令
[root@hadoop101 mycentos]# docker run -it mysentos:1.0[root@2f70cc22b493 local]# pwd/usr/local[root@2f70cc22b493 local]# llbash: ll: command not found[root@2f70cc22b493 local]# vim test[root@2f70cc22b493 local]# ifconfigeth0: 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 8 bytes 656 (656.0 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 0lo: 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@2f70cc22b493 local]#可以看到 vim 和 ifconfig 命令已经可以使用，ll 命令还需要下载对应的工具包，这里就不在下载了。
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