1.看完docker容器基本架构和基本知识（一定要看官网英文版，讲的清楚）
2.动手实践一下
A.创建Dockerfile
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]# cat Dockerfile
FROM centos
LABEL maintainer="[email protected]"
RUN yum -y install expect \
&& yum -y install dos2unix
#再容器中创建shell_test_docker并改变权限
RUN mkdir shell_test_docker \
&& chmod 777 shell_test_docker
#将Dockerfile所在路径下的shell_test内容（该目录下只有一个print_test.sh脚本）拷贝到容器目录shell_test_docker
COPY ./shell_test shell_test_docker
#指定后续容器运行时需要执行的上下文目录
WORKDIR shell_test_docker
RUN chmod 777 print_test.sh \
&& cd /shell_test_docker \
&& ./print_test.sh
ENTRYPOINT ["./print_test.sh"]
B.build 镜像
docker build -t zw_shell_test:v1 .
下面是build打印：
Sending build context to Docker daemon 4.096kB
Step 1/8 : FROM centos
---> 0f3e07c0138f
Step 2/8 : LABEL maintainer="[email protected]"
---> Running in 0103bb129716
Removing intermediate container 0103bb129716
---> 33085ff163d1
Step 3/8 : RUN yum -y install expect && yum -y install dos2unix
---> Running in f973384ac248
CentOS-8 - AppStream 2.6 MB/s | 6.3 MB 00:02
CentOS-8 - Base 3.5 MB/s | 7.9 MB 00:02
CentOS-8 - Extras 101 B/s | 2.1 kB 00:21
Dependencies resolved.
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
expect x86_64 5.45.4-5.el8 BaseOS 267 k
Installing dependencies:
tcl x86_64 1:8.6.8-2.el8 BaseOS 1.1 M
Transaction Summary
================================================================================
Install 2 Packages
Total download size: 1.4 M
Installed size: 4.7 M
Downloading Packages:
[MIRROR] tcl-8.6.8-2.el8.x86_64.rpm: Curl error (56): Failure when receiving data from the peer for http://mirror.lzu.edu.cn/centos/8.0.1905/BaseOS/x86_64/os/Packages/tcl-8.6.8-2.el8.x86_64.rpm [Recv failure: Connection reset by peer]
(1/2): expect-5.45.4-5.el8.x86_64.rpm 731 kB/s | 267 kB 00:00
(2/2): tcl-8.6.8-2.el8.x86_64.rpm 420 kB/s | 1.1 MB 00:02
--------------------------------------------------------------------------------
Total 330 kB/s | 1.4 MB 00:04
warning: /var/cache/dnf/BaseOS-f6a80ba95cf937f2/packages/expect-5.45.4-5.el8.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 8483c65d: NOKEY
CentOS-8 - Base 1.6 MB/s | 1.6 kB 00:00
Importing GPG key 0x8483C65D:
Userid : "CentOS (CentOS Official Signing Key) <[email protected]>"
Fingerprint: 99DB 70FA E1D7 CE22 7FB6 4882 05B5 55B3 8483 C65D
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
Preparing : 1/1
Installing : tcl-1:8.6.8-2.el8.x86_64 1/2
Running scriptlet: tcl-1:8.6.8-2.el8.x86_64 1/2
Installing : expect-5.45.4-5.el8.x86_64 2/2
Running scriptlet: expect-5.45.4-5.el8.x86_64 2/2
Verifying : expect-5.45.4-5.el8.x86_64 1/2
Verifying : tcl-1:8.6.8-2.el8.x86_64 2/2
Installed:
expect-5.45.4-5.el8.x86_64 tcl-1:8.6.8-2.el8.x86_64
Complete!
Last metadata expiration check: 0:00:06 ago on Tue Dec 3 08:23:28 2019.
Dependencies resolved.
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
dos2unix x86_64 7.4.0-3.el8 BaseOS 241 k
Transaction Summary
================================================================================
Install 1 Package
Total download size: 241 k
Installed size: 666 k
Downloading Packages:
dos2unix-7.4.0-3.el8.x86_64.rpm 634 kB/s | 241 kB 00:00
--------------------------------------------------------------------------------
Total 104 kB/s | 241 kB 00:02
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
Preparing : 1/1
Installing : dos2unix-7.4.0-3.el8.x86_64 1/1
Running scriptlet: dos2unix-7.4.0-3.el8.x86_64 1/1
Verifying : dos2unix-7.4.0-3.el8.x86_64 1/1
Installed:
dos2unix-7.4.0-3.el8.x86_64
Complete!
Removing intermediate container f973384ac248
---> 78a662cb3b01
Step 4/8 : RUN mkdir shell_test_docker && chmod 777 shell_test_docker
---> Running in 7f6794c8d204
Removing intermediate container 7f6794c8d204
---> 3c8c4769b02d
Step 5/8 : COPY ./shell_test shell_test_docker
---> a0205096dfcb
Step 6/8 : WORKDIR shell_test_docker
---> Running in ceb35e80cbe0
Removing intermediate container ceb35e80cbe0
---> aedf9fb069bb
Step 7/8 : RUN chmod 777 print_test.sh && cd /shell_test_docker && ./print_test.sh
---> Running in 92e5e4069eab
hello dockter //此处为print_test.sh打印的内容，说明目录进出访问执行都没有问题
Removing intermediate container 92e5e4069eab
---> 62ca449639e8
Step 8/8 : ENTRYPOINT ["print_test.sh"]
---> Running in 0ed2a73aeeca
Removing intermediate container 0ed2a73aeeca
---> 9dde304179dc
Successfully built 9dde304179dc
Successfully tagged zw_shell_test:v1
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]#
C.运行image
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]# docker image list
REPOSITORY TAG IMAGE ID CREATED SIZE
zw_shell_test v1 9dde304179dc About a minute ago 266MB
centos latest 0f3e07c0138f 2 months ago 220MB
docker run -d 9dde304179dc //后台运行
报错如下：反复都查找不到原因
d2f5b90ee9db112253f9d66130a0463c1b530d8a540359be04301eb19bb2d403
docker: Error response from daemon: OCI runtime create failed: container_linux.go:346: starting container process caused "exec: \"print_test.sh\": executable file not found in $PATH": unknown.
查了很多资料，说是路径或权限的问题，干脆从新修改Dockerfile，删除最后一行：ENTRYPOINT ["./print_test.sh"]，再次运行进去看看该脚本到底有没有执行权限以及目录问题
重新编译
再次运行：docker container run -idt 37ff5cc05f28 //该命令是后台shell的方式运行image，便于调试，和一般运行参数不同
//发现up成功了，说明是那条ENTRYPOINT使用有问题
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
f69659e40111 37ff5cc05f28 "/bin/bash" 30 seconds ago Up 29 seconds silly_varahamihira
再次进入该容器：docker container exec -it f69659e40111 bash
//发现容器内当前路径确实是我们在Dockerfile中WORKDIR设置的默认路径
[root@f69659e40111 shell_test_docker]# pwd
/shell_test_docker
[root@f69659e40111 shell_test_docker]# ls -al
total 12
drwxrwxrwx 1 root root 4096 Dec 3 08:31 .
drwxr-xr-x 1 root root 4096 Dec 3 08:33 ..
-rwxrwxrwx 1 root root 31 Dec 3 02:34 print_test.sh //在容器中查看该脚本权限也是可读可写可执行，那为什么原Dockerfile报错呢
[root@f69659e40111 shell_test_docker]# ./print_test.sh //在容器中执行该脚本也能顺利执行，那到底为什么原Dockerfile报错
hello dockter
问题解决：
docker image inspect zw_shell_test:v1,
看查是路径似乎不对
将ENTRYPOINT ["./print_test.sh"] 修改成ENTRYPOINT ["print_test.sh"]
重编译一下
docker stop $(docker ps -q) & docker rm $(docker ps -aq) //删除所有已经运行的容器
docker image rm 744c0eba96fe //删除旧的image
docker build -t zw_shell_test:v1 . //再次编译
docker run -d zw_shell_test:v1 //运行image
还是出现：
docker: Error response from daemon: OCI runtime create failed: container_linux.go:346: starting container process caused "exec: \"print_test.sh\": executable file not found in $PATH": unknown.
既然目录和路径执行权限都对，看到提示$PATH，那么是不是环境变量有问题呢，再次docker image inspect zw_shell_test:v1,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" //这里并没有我们要执行的脚本路径
],
"Cmd": null,
所以我们尝试一下添加执行脚本的环境变量看看，在Dockerfile中添加一行：
ENV PATH /shell_test_docker:$PATH //将shell所在路径添加到环境变量目录路径中
重编后再次docker image inspect zw_shell_test:v1,
"Env": [
"PATH=/shell_test_docker:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" //这里出现要执行的脚本路径
],
"Cmd": null,
再次运行image
container ps -al
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]# docker ps -al
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b202e5b4f82b zw_shell_test:v1 "print_test.sh" 5 minutes ago Exited (0) 5 minutes ago nervous_cohen
发现虽然没报错，但是出于Exited状态。百思不得其解。
查了很多资料，包括官网文档，发现Entrypoint其实相当于main函数，main执行完了，进程就退出了，Entrypoint也是这样。所以执行完shell脚本就退出了，这个状态是对的。
C.下面我们写一段代码，保持主循环，再从Entrypoint启动。
再shell_test目录下添加测试代码test.c并编译成test执行程序：
[root@iZbp1g8nzni5lhsdvd3a6aZ shell_test]# cat test.c
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int main()
{
while(1)
{
}
return 1;
}
修改Dockerfile如下：
#test for omm
FROM centos
LABEL maintainer="[email protected]"
RUN yum -y install expect \
&& yum -y install dos2unix
#拷贝Dockerfile所在目录下CNV4WG文件夹到运行容易目录中
RUN mkdir shell_test_docker \
&& chmod 777 shell_test_docker
COPY ./shell_test shell_test_docker
#设置环境变量，后续函数入口默认调用程序先从这里找
ENV PATH /shell_test_docker:$PATH
#设置容器工作目录，进入容器后默认就是该目录
WORKDIR shell_test_docker
RUN chmod 777 print_test.sh \
&& ./print_test.sh //注意改行是之前执行的脚本，执行脚本之类的我们可以使用run执行即可
ENTRYPOINT ["./test"] //启动一个不会执行退出的应用程序
重编译发现问题：
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]# docker build -t zw_shell_test:v1 .
Sending build context to Docker daemon 15.36kB
Step 1/9 : FROM centos
---> 0f3e07c0138f
Step 2/9 : LABEL maintainer="[email protected]"
---> Running in 4719322c9603
Removing intermediate container 4719322c9603
---> b9b54d7c3938
Step 3/9 : RUN yum -y install expect && yum -y install dos2unix
---> Running in 16692b61fee5
CentOS-8 - AppStream 571 kB/s | 6.3 MB 00:11
CentOS-8 - Base 0.0 B/s | 0 B 00:23
CentOS-8 - Extras 2.5 kB/s | 2.1 kB 00:00
Failed to synchronize cache for repo 'BaseOS', ignoring this repo.
No match for argument: expect
Error: Unable to find a match
The command '/bin/sh -c yum -y install expect && yum -y install dos2unix' returned a non-zero code: 1 //单独执行可以成功，有可能是云环境网络出现问题。
重新编译一次，发现变成成功。然后再次启动image。
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
12d42e366c07 zw_shell_test:v1 "./test" 16 seconds ago Up 15 seconds vigilant_khayyam
为UP状态，我们自制的容器启动成功了。
下面进去一探，后台shell执行进去。
docker container exec -it 12d42e366c07 bash
[root@iZbp1g8nzni5lhsdvd3a6aZ script_test]# docker container exec -it 12d42e366c07 bash
[root@12d42e366c07 shell_test_docker]# pwd
/shell_test_docker
[root@12d42e366c07 shell_test_docker]# ls -al
total 32
drwxrwxrwx 1 root root 4096 Dec 4 06:52 .
drwxr-xr-x 1 root root 4096 Dec 4 06:53 ..
-rwxrwxrwx 1 root root 55 Dec 3 11:24 print_test.sh
-rwxr-xr-x 1 root root 9536 Dec 4 02:21 test
-rw-r--r-- 1 root root 106 Dec 4 02:21 test.c
drwxr-xr-x 2 root root 4096 Dec 4 06:52 test_test_Test
[root@12d42e366c07 shell_test_docker]# cat print_test.sh
#!/bin/bash
mkdir test_test_Test
[root@12d42e366c07 shell_test_docker]# expect
expect1.1>
[root@12d42e366c07 shell_test_docker]# dos2unix --help
Usage: dos2unix [options] [file ...] [-n infile outfile ...][root@12d42e366c07 shell_test_docker]# export
declare -x HOME="/root"
declare -x HOSTNAME="12d42e366c07"
declare -x LANG="en_US.UTF-8"
declare -x LESSOPEN="||/usr/bin/lesspipe.sh %s"
declare -x OLDPWD
declare -x PATH="/shell_test_docker:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" //我们Dockerfile中定义的环境变量
declare -x PWD="/shell_test_docker"
declare -x SHLVL="1"
declare -x TERM="xterm"
发现我们在Dockerfile执行的东西都已经存在在容器中了。
总结：初探容器的使用，发现容器真是太强大了，可以在一台机器上构建自己不同的应用，无数个开发者可以在其中构建自己的开发环境。