DockerFile介绍——指令——实战1——CMD与ENTRYPOINT的区别——实战2

dockerfile 是用来构建docker镜像的文件! 命令参数脚本!
构建步骤：
1、编写一个 dockerfile 文件
2、docker build 构建成为一个镜像
3、docker run 运行镜像
4、docker push 发布镜像（dockerHub 、 阿里云镜像仓库）

基础知识：
1、每个保留关键字（指令）都必须是大写字母
2、执行从上到下顺序执行
3、#表示注释
4、每一个指令都会创建提交一个新的镜像层，并提交！

dockerfile是面向开发的,我们以后要发布项目,做镜像，就需要编写Dockerfile文件，这个文件十分简单
Docker镜像逐渐成为了企业交付的标准，必须要掌握!
步骤：开发，部署，运维 缺一不可
DockerFile：构建文件，定义了一切的步骤，源代码
Dockerimages：通过DockerFile 构建生成的镜像，最终发布和运行的产品
Docker容器：镜像运行起来提供服务的

FROM                         #基础镜像，一切从这里开始构建
MAINTAINER             # 镜像是谁写的，姓名+邮箱
RUN                           # 镜像构建的时候需要运行的命令
ADD                           #步骤 tomcat镜像 这个tomcat压缩包! 添加内容
WORKDIR                  #镜像的工作目录
VOLUME                    # 挂载到哪儿个目录位置
EXPOST                     # 暴露端口配置
CMD                          # 指定这个容器启动的时候要运行的命令  只有最后一个会生效，可被替代
ENTRYPOINT             # 指定这个容器启动的时候要运行的命令，可以追加命令
ONBUILD                   # 当构建一个被继承 DockerFile 这个时候就会运行 ONBUILD 的指令 ， 触发指令
COPY                         # 类似 ADD ， 将我们文件拷贝到镜像中
ENV                            # 构建的时候设置环境变量!   

Docker Hub 中 99% 镜像都是从这个基础镜像过来的from scratch  然后配置需要的软件和配置来进行的构建

创建一个自己的centos  编写一个 工作路径在/usr/local  ，安装了vim 和 ifconfig 功能的镜像

vim /home/dockerfile/mydockerfile-centos 
[root@localhost dockerfile]# cat mydockerfile-centos 
FROM centos:7
MAINTAINER laoba<2658994997@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 "----end----"
CMD /bin/bash 

  命令 docker build -f  mydockerfile-centos  -t mycentos .  
（前提有centos:7版本的镜像，没有的 docker pull centos:7 下载一个）

# 测试
[root@localhost dockerfile]# docker run -it mycentos
[root@0e2e34546251 local]# pwd
/usr/local
[root@0e2e34546251 local]# vim

  

~                                                                         
~                           VIM - Vi IMproved                             
~                                                                         
~                            version 7.4.629                              
~                        by Bram Moolenaar et al.                         
~                   Modified by                      
~              Vim is open source and freely distributable                
~                                                                         
~                        Sponsor Vim development!                         
~             type  :help sponsor    for information               
~                                                                         
~             type  :q               to exit                       
~             type  :help  or    for on-line help              
~             type  :help version7   for version info              
~                                                                         
~                                                                         
[root@71b3213cb3bd local]# ifconfig
eth0: 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 7  bytes 586 (586.0 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

lo: 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@71b3213cb3bd local]# 


docker histroy 镜像ID  查看镜像制作步骤

CMD                   # 指定这个容器启动的时候要运行的命令，只有最后一个会生效，可被替代
ENTRYPOINT      # 指定这个容器启动的 时候要运行的命令，可以追加命令

1、编写 dockerfile 文件

[root@localhost dockerfile]# cat dockerfile-cmd-test 
FROM centos
CMD ["ls","-a"]

2、构建镜像

[root@localhost dockerfile]# docker run -it cmdtest

3、run运行  发现我们的ls -a 命令生效

[root@localhost dockerfile]# docker run -it cmdtest
WARNING: IPv4 forwarding is disabled. Networking will not work.
.   .dockerenv  dev  home  lib64       media  opt   root  sbin  sys  usr
..  bin         etc  lib   lost+found  mnt    proc  run   srv   tmp  var

4、想追加一个命令  -l   ls -al

[root@localhost dockerfile]# docker run cmdtest -l
WARNING: IPv4 forwarding is disabled. Networking will not work.
docker: Error response from daemon: failed to create shim: OCI runtime create failed: container_linux.go:380: starting container process caused: exec: "-l": executable file not found in $PATH: unknown.
ERRO[0000] error waiting for container: context canceled 

5、# cmd的情况下 -l 替换了CMD ["ls","-a"] 命令 ,-l 不是命令所以报错 !
      正确写法是： docker run  cmdtext ls -al

[root@localhost dockerfile]# docker run cmdtest ls -al
total 0
drwxr-xr-x.   1 root root   6 May 15 12:31 .
drwxr-xr-x.   1 root root   6 May 15 12:31 ..
-rwxr-xr-x.   1 root root   0 May 15 12:31 .dockerenv
lrwxrwxrwx.   1 root root   7 Nov  3  2020 bin -> usr/bin
drwxr-xr-x.   5 root root 340 May 15 12:31 dev
drwxr-xr-x.   1 root root  66 May 15 12:31 etc
drwxr-xr-x.   2 root root   6 Nov  3  2020 home
lrwxrwxrwx.   1 root root   7 Nov  3  2020 lib -> usr/lib
lrwxrwxrwx.   1 root root   9 Nov  3  2020 lib64 -> usr/lib64
drwx------.   2 root root   6 Sep 15  2021 lost+found
drwxr-xr-x.   2 root root   6 Nov  3  2020 media
drwxr-xr-x.   2 root root   6 Nov  3  2020 mnt
drwxr-xr-x.   2 root root   6 Nov  3  2020 opt
dr-xr-xr-x. 235 root root   0 May 15 12:31 proc
dr-xr-x---.   2 root root 162 Sep 15  2021 root
drwxr-xr-x.  11 root root 163 Sep 15  2021 run
lrwxrwxrwx.   1 root root   8 Nov  3  2020 sbin -> usr/sbin
drwxr-xr-x.   2 root root   6 Nov  3  2020 srv
dr-xr-xr-x.  13 root root   0 May  2 07:13 sys
drwxrwxrwt.   7 root root 171 Sep 15  2021 tmp
drwxr-xr-x.  12 root root 144 Sep 15  2021 usr
drwxr-xr-x.  20 root root 262 Sep 15  2021 var
[root@localhost dockerfile]# 

[root@localhost dockerfile]# vim dockerfile-cmd-entrypoint
FROM centos
ENTRYPOINT ["ls","-a"]
[root@localhost dockerfile]# docker build -f dockerfile-cmd-entrypoint -t  entrypoint-test .
Sending build context to Docker daemon  4.096kB
Step 1/2 : FROM centos
 ---> 5d0da3dc9764
Step 2/2 : ENTRYPOINT ["ls","-a"]
 ---> [Warning] IPv4 forwarding is disabled. Networking will not work.
 ---> Running in 4ada8776f743
Removing intermediate container 4ada8776f743
 ---> 96d79621f6d6
Successfully built 96d79621f6d6
Successfully tagged entrypoint-test:latest
[root@localhost dockerfile]# docker run -it entrypoint-test
WARNING: IPv4 forwarding is disabled. Networking will not work.
.   .dockerenv  dev  home  lib64       media  opt   root  sbin  sys  usr
..  bin         etc  lib   lost+found  mnt    proc  run   srv   tmp  var

# 我们的追加命令，是直接拼接在我们的 ENTRYPOINT 命令的后面!

[root@localhost dockerfile]# docker run entrypoint-test -l
WARNING: IPv4 forwarding is disabled. Networking will not work.
total 0
drwxr-xr-x.   1 root root   6 May 15 11:50 .
drwxr-xr-x.   1 root root   6 May 15 11:50 ..
-rwxr-xr-x.   1 root root   0 May 15 11:50 .dockerenv
lrwxrwxrwx.   1 root root   7 Nov  3  2020 bin -> usr/bin
drwxr-xr-x.   5 root root 340 May 15 11:50 dev
drwxr-xr-x.   1 root root  66 May 15 11:50 etc
drwxr-xr-x.   2 root root   6 Nov  3  2020 home
lrwxrwxrwx.   1 root root   7 Nov  3  2020 lib -> usr/lib
lrwxrwxrwx.   1 root root   9 Nov  3  2020 lib64 -> usr/lib64
drwx------.   2 root root   6 Sep 15  2021 lost+found
drwxr-xr-x.   2 root root   6 Nov  3  2020 media
drwxr-xr-x.   2 root root   6 Nov  3  2020 mnt
drwxr-xr-x.   2 root root   6 Nov  3  2020 opt
dr-xr-xr-x. 233 root root   0 May 15 11:50 proc
dr-xr-x---.   2 root root 162 Sep 15  2021 root
drwxr-xr-x.  11 root root 163 Sep 15  2021 run
lrwxrwxrwx.   1 root root   8 Nov  3  2020 sbin -> usr/sbin
drwxr-xr-x.   2 root root   6 Nov  3  2020 srv
dr-xr-xr-x.  13 root root   0 May  2 07:13 sys
drwxrwxrwt.   7 root root 171 Sep 15  2021 tmp
drwxr-xr-x.  12 root root 144 Sep 15  2021 usr
drwxr-xr-x.  20 root root 262 Sep 15  2021 var
[root@localhost dockerfile]#

待更新