CMD和ENTRYPOINT的区别

CMD测试

编写dockerfile文件

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# cat CMDos 
FROM centos:7

CMD ["ls","-a"]

构建镜像

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# docker build -f CMDos -t cmdos:1.0 .

启动镜像

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# docker run -it 7083385c1517
.   .dockerenv	       bin  etc   lib	 media	opt   root  sbin  sys  usr
..  anaconda-post.log  dev  home  lib64  mnt	proc  run   srv   tmp  var

发现启动镜像时，执行了CMD命令
我们尝试在启动镜像时追加命令 发现报错

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# docker run 7083385c1517 -l
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.

ENTRYPOINT测试编写

dockerfile文件

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# cat ENTRYPOINTos 
FROM centos

ENTRYPOINT ["ls","-a"]

构建镜像

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# docker build -f ENTRYPOINTos . # 没有指定镜像名和版本号（建议设置tag）
Sending build context to Docker daemon  4.096kB
Step 1/2 : FROM centos
 ---> 5d0da3dc9764
Step 2/2 : ENTRYPOINT ["ls","-a"]
 ---> Running in a9e6cee88acf
Removing intermediate container a9e6cee88acf
 ---> c7f77b087635
Successfully built c7f77b087635

运行镜像

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# docker run -it c7f77b087635 
.  ..  .dockerenv  bin	dev  etc  home	lib  lib64  lost+found	media  mnt  opt  proc  root  run  sbin	srv  sys  tmp  usr  var

发现在运行镜像后，执行了ENTRYPOINT命令

到这里好像和CMD命令没有区别

在运行ENTRYPOINT镜像时，追加命令

[root@iZbp1htnoa70qlle394f3wZ dockerfile]# docker run c7f77b087635 -l
total 56
drwxr-xr-x   1 root root 4096 Apr 23 01:59 .
drwxr-xr-x   1 root root 4096 Apr 23 01:59 ..
-rwxr-xr-x   1 root root    0 Apr 23 01:59 .dockerenv
lrwxrwxrwx   1 root root    7 Nov  3  2020 bin -> usr/bin
drwxr-xr-x   5 root root  340 Apr 23 01:59 dev
drwxr-xr-x   1 root root 4096 Apr 23 01:59 etc
drwxr-xr-x   2 root root 4096 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 4096 Sep 15  2021 lost+found
drwxr-xr-x   2 root root 4096 Nov  3  2020 media
drwxr-xr-x   2 root root 4096 Nov  3  2020 mnt
drwxr-xr-x   2 root root 4096 Nov  3  2020 opt
dr-xr-xr-x 103 root root    0 Apr 23 01:59 proc
dr-xr-x---   2 root root 4096 Sep 15  2021 root
drwxr-xr-x  11 root root 4096 Sep 15  2021 run
lrwxrwxrwx   1 root root    8 Nov  3  2020 sbin -> usr/sbin
drwxr-xr-x   2 root root 4096 Nov  3  2020 srv
dr-xr-xr-x  13 root root    0 Apr 21 15:07 sys
drwxrwxrwt   7 root root 4096 Sep 15  2021 tmp
drwxr-xr-x  12 root root 4096 Sep 15  2021 usr
drwxr-xr-x  20 root root 4096 Sep 15  2021 var

这时区别就出来了，ENTRYPOINT可以在运行时追加参数，而CMD不行