1）目标：自定义镜像
wokong_centos。2）所用到的保留字指令：
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（端口映射）。WORKDIR：指定在创建容器后，终端默认登陆进来的工作目录，一个落脚点，也就是pwd的位置。ENV：用来在构建镜像过程中设置环境变量。CMD：指定一个容器启动时要运行的命令。3）新Docker命令：
docker history，查看镜像的变更历史。
我们运行官方的CentOS镜像。
# 1.查看本地Docker镜像[root@192 home]# docker imagesREPOSITORY TAG IMAGE ID CREATED SIZEcentos latest 300e315adb2f 3 months ago 209MB# 2.查看正确运行的Docker容器，此时没有容器正在运行。[root@192 home]# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES# 3.启动centos镜像[root@192 home]# docker run -it centos[root@ed92adeebf72 /]# # 4.在容器中执行如下操作# 4.1 查看容器当前工作目录，在根目录[root@ed92adeebf72 /]# pwd/# 4.2 使用vim命令编辑文件，发现没有vim命令[root@ed92adeebf72 /]# vim abc.txtbash: vim: command not found# 4.3 查看Docker容器的IP地址，发现无法使用ifconfig命令。[root@ed92adeebf72 /]# ifconfigbash: ifconfig: command not found出现以上问题是因为，CentOS方镜像为了保证镜像的大小，是使用最小启动系统的精简版Linux系统，其中会有很多命令没有。
所以，自定义wokong_centos镜像的目的，使我们自己的镜像具备如下：
/tmp。vim编辑器。ifconfig命令。在宿主机的home目录中创建mydockerfile文件夹，用于存放我们编写的Dockerfile文件。
# 创建mydockerfile文件夹[root@192 home]# ll总用量 0[root@192 home]# mkdir mydockerfile[root@192 home]# ll总用量 0drwxr-xr-x. 2 root root 6 3月 20 14:59 mydockerfile# 创建dockerfile文件:Dockerfile_centos# 作为wokong_centos镜像的dockerfile文件。[root@192 mydockerfile]# vim Dockerfile_centos提示：Dockerfile文件可以自定义。
Dockerfile文件内容如下：
FROM centos # 继承了本地的centos镜像MAINTAINER wukong<wukong6688@126.com> # 镜像作者的名字和邮箱信息ENV MYPATH /tmp # 配置环境变量,是一个key：value模式的键值对存储。也可以用=号。WORKDIR $MYPATH # 定义容器初始工作目录，并引用了上边的ENV变量。RUN yum -y install vim # 容器构建时需要运行的命令。RUN yum -y install net-toolsEXPOSE 80 # 暴露80端口到服务器CMD echo "success---------ok"CMD /bin/bash说明：
我自定义的
wokong_centos镜像是以CentOS官方镜像为基础进行修改的。而CentOS官方镜像的Base镜像是
FROM scratch。Docker Hub中99%的镜像都是通过
scratch镜像，作为最底层的镜像，然后安装和配置出所需要的软件，最后得到我们需要的镜像。（
scratch镜像是一个空的镜像，可以真正的从零开始构建属于自己的镜像。）
执行命令：docker build -f Dockerfile文件路径 -t 新镜像名字:TAG .
安装过程如下：
# 完整安装过程[root@192 mydockerfile]# docker build -f /home/mydockerfile/Dockerfile_centos \> -t wokong_centos:1.6 .Sending build context to Docker daemon 2.048kBStep 1/9 : FROM centos ---> 300e315adb2fStep 2/9 : MAINTAINER wukong<wukong6688@126.com> ---> Running in 38481c4819a3Removing intermediate container 38481c4819a3 ---> 96a9036d8cadStep 3/9 : ENV MYPATH /tmp ---> Running in bb236291ff01Removing intermediate container bb236291ff01 ---> 6cf48c1a740aStep 4/9 : WORKDIR $MYPATH ---> Running in 15ce861a59c1Removing intermediate container 15ce861a59c1 ---> 537898233556Step 5/9 : RUN yum -y install vim ---> Running in 99f06b342bf8CentOS Linux 8 - AppStream 1.8 MB/s | 6.3 MB 00:03CentOS Linux 8 - BaseOS 1.7 MB/s | 2.3 MB 00:01CentOS Linux 8 - Extras 13 kB/s | 9.2 kB 00:00Last metadata expiration check: 0:00:01 ago on Sat Mar 20 08:10:25 2021.Dependencies resolved.================================================================================ Package Arch Version Repository Size================================================================================Installing: vim-enhanced x86_64 2:8.0.1763-15.el8 appstream 1.4 MInstalling dependencies: gpm-libs x86_64 1.20.7-15.el8 appstream 39 k vim-common x86_64 2:8.0.1763-15.el8 appstream 6.3 M vim-filesystem noarch 2:8.0.1763-15.el8 appstream 48 k which x86_64 2.21-12.el8 baseos 49 kTransaction Summary================================================================================Install 5 PackagesTotal download size: 7.8 MInstalled size: 30 MDownloading Packages:(1/5): gpm-libs-1.20.7-15.el8.x86_64.rpm 157 kB/s | 39 kB 00:00(2/5): vim-enhanced-8.0.1763-15.el8.x86_64.rpm 3.0 MB/s | 1.4 MB 00:00(3/5): vim-filesystem-8.0.1763-15.el8.noarch.rp 181 kB/s | 48 kB 00:00(4/5): which-2.21-12.el8.x86_64.rpm 122 kB/s | 49 kB 00:00(5/5): vim-common-8.0.1763-15.el8.x86_64.rpm 5.7 MB/s | 6.3 MB 00:01--------------------------------------------------------------------------------Total 1.5 MB/s | 7.8 MB 00:05CentOS Linux 8 - AppStream 1.6 MB/s | 1.6 kB 00:00warning: /var/cache/dnf/appstream-02e86d1c976ab532/packages/gpm-libs-1.20.7-15.el8.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 8483c65d: NOKEYImporting GPG key 0x8483C65D: Userid : "CentOS (CentOS Official Signing Key) <security@centos.org>" Fingerprint: 99DB 70FA E1D7 CE22 7FB6 4882 05B5 55B3 8483 C65D From : /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-2.21-12.el8.x86_64 1/5 Installing : vim-filesystem-2:8.0.1763-15.el8.noarch 2/5 Installing : vim-common-2:8.0.1763-15.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-2:8.0.1763-15.el8.x86_64 5/5 Running scriptlet: vim-enhanced-2:8.0.1763-15.el8.x86_64 5/5 Running scriptlet: vim-common-2:8.0.1763-15.el8.x86_64 5/5 Verifying : gpm-libs-1.20.7-15.el8.x86_64 1/5 Verifying : vim-common-2:8.0.1763-15.el8.x86_64 2/5 Verifying : vim-enhanced-2:8.0.1763-15.el8.x86_64 3/5 Verifying : vim-filesystem-2:8.0.1763-15.el8.noarch 4/5 Verifying : which-2.21-12.el8.x86_64 5/5Installed: gpm-libs-1.20.7-15.el8.x86_64 vim-common-2:8.0.1763-15.el8.x86_64 vim-enhanced-2:8.0.1763-15.el8.x86_64 vim-filesystem-2:8.0.1763-15.el8.noarch which-2.21-12.el8.x86_64Complete!Removing intermediate container 99f06b342bf8 ---> c58485da8447Step 6/9 : RUN yum -y install net-tools ---> Running in a5e4191e9fb2Last metadata expiration check: 0:00:19 ago on Sat Mar 20 08:10:25 2021.Dependencies resolved.================================================================================ Package Architecture Version Repository Size================================================================================Installing: net-tools x86_64 2.0-0.52.20160912git.el8 baseos 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 1.7 MB/s | 322 kB 00:00--------------------------------------------------------------------------------Total 195 kB/s | 322 kB 00:01Running 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 1/1 Installed: net-tools-2.0-0.52.20160912git.el8.x86_64Complete!Removing intermediate container a5e4191e9fb2 ---> 5e7dba859606Step 7/9 : EXPOSE 80 ---> Running in e5b3c11088d3Removing intermediate container e5b3c11088d3 ---> 5d8199d84409Step 8/9 : CMD echo "success---------ok" ---> Running in 0d8b83e6008bRemoving intermediate container 0d8b83e6008b ---> 94ff44f5e94cStep 9/9 : CMD /bin/bash ---> Running in 31a13253e359Removing intermediate container 31a13253e359 ---> 6441f63090d4Successfully built 6441f63090d4Successfully tagged wokong_centos:1.6# 查看本地Docker镜像。[root@192 mydockerfile]# docker imagesREPOSITORY TAG IMAGE ID CREATED SIZEwokong_centos 1.6 6441f63090d4 10 seconds ago 291MBcentos latest 300e315adb2f 3 months ago 209MB我们可以看到新构建的wokong_centos镜像，比官方CentOS镜像多了80多M。
说明：
docker build命令最后有一个.，这个.有的说表示当前目录，有的说表示将当前目录的上下文路径中使用Dockerfile构建。安装后一种说法，上面的构建命令中，
.也可以替换成/home/mydockerfile/。（我尝试了，可行）但你就记住是固定写法就好了。
我们把刚刚构建的wokong_centos镜像启动起来。
# 启动进入wokong_centos容器[root@192 mydockerfile]# docker run -it wokong_centos:1.6[root@55e0b688c9fb tmp]## 1.查看默认工作路径[root@55e0b688c9fb tmp]# pwd/tmp# 2.查看当前容器IP[root@55e0b688c9fb tmp]# 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# 3.查看是否可以使用vim编辑器[root@55e0b688c9fb tmp]# vim --helpVIM - Vi IMproved 8.0 (2016 Sep 12, compiled Jun 18 2020 15:49:08)usage: vim [arguments] [file ..] edit specified file(s) or: vim [arguments] - read text from stdin or: vim [arguments] -t tag edit file where tag is defined or: vim [arguments] -q [errorfile] edit file with first error我们可以看到，进入容器的默认工作目录变成了/tmp目录了，而不是之前根目录了。
同时ifconfig命令，和vim编辑器都可以使用了。
命令：docker history 镜像名/ID。
作用：可以列出本地镜像的变更历史。
示例：
# 查看本地Docker镜像[root@192 mydockerfile]# docker imagesREPOSITORY TAG IMAGE ID CREATED SIZEwokong_centos 1.6 6441f63090d4 17 minutes ago 291MBcentos latest 300e315adb2f 3 months ago 209MB# 查看wokong_centos镜像的变更历史[root@192 mydockerfile]# docker history wokong_centos:1.6 IMAGE CREATED CREATED BY SIZE COMMENT6441f63090d4 18 minutes ago /bin/sh -c #(nop) CMD ["/bin/sh" "-c" "/bin… 0B94ff44f5e94c 18 minutes ago /bin/sh -c #(nop) CMD ["/bin/sh" "-c" "echo… 0B5d8199d84409 18 minutes ago /bin/sh -c #(nop) EXPOSE 80 0B5e7dba859606 18 minutes ago /bin/sh -c yum -y install net-tools 23.3MBc58485da8447 18 minutes ago /bin/sh -c yum -y install vim 58MB537898233556 18 minutes ago /bin/sh -c #(nop) WORKDIR /tmp 0B6cf48c1a740a 18 minutes ago /bin/sh -c #(nop) ENV MYPATH=/tmp 0B96a9036d8cad 18 minutes ago /bin/sh -c #(nop) MAINTAINER wukong<wukong6… 0B300e315adb2f 3 months ago /bin/sh -c #(nop) CMD ["/bin/bash"] 0B<missing> 3 months ago /bin/sh -c #(nop) LABEL org.label-schema.sc… 0B<missing> 3 months ago /bin/sh -c #(nop) ADD file:bd7a2aed6ede423b7… 209MB