The difference between CMD and ENTRYPOINT
# CMD测试
# 1.编写dockerfile-cmd使用CMD命令，在容器运行后自动运行ls -a命令
[root@amumu zzl-dockerfile]# cat dockerfile-cmd
FROM centos
MAINTAINER zhuzhonglang<[email protected]>
CMD ["ls","-a"]
# 2.构建镜像
[root@amumu zzl-dockerfile]# docker build -f dockerfile-cmd -t dockercmd-test:1.0 .
Sending build context to Docker daemon 3.072kB
Step 1/3 : FROM centos
---> 300e315adb2f
Step 2/3 : MAINTAINER zhuzhonglang<[email protected]>
---> Using cache
---> 313fbe570c8d
Step 3/3 : CMD ["ls","-a"]
---> Running in 6f376bf9727a
Removing intermediate container 6f376bf9727a
---> 50e092624b77
Successfully built 50e092624b77
Successfully tagged dockercmd-test:1.0
[root@amumu zzl-dockerfile]#
# 3.运行刚刚创建的镜像，运行镜像后，自动执行了ls -a命令
[root@amumu zzl-dockerfile]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
dockercmd-test 1.0 50e092624b77 18 seconds ago 209MB
mycentos 1.0 ff0a2b5b0669 5 hours ago 291MB
mysql 5.7 87eca374c0ed 3 weeks ago 447MB
nginx latest 62d49f9bab67 4 weeks ago 133MB
centos latest 300e315adb2f 5 months ago 209MB
[root@amumu zzl-dockerfile]# docker run 50e092624b77
..
.dockerenv
bin
dev
etc
home
lib
lib64
lost+found
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var
# 4.运行镜像，并在镜像后面加上-l ,这时并没有按照理想中的情况自动执行ls -al命令，而是报错了
[root@amumu zzl-dockerfile]# docker run 50e092624b77 -l
docker: Error response from daemon: OCI runtime create failed: container_linux.go:367: starting container process caused: exec: "-l": executable file not found in $PATH: unknown.
# 5.运行镜像，并在镜像后面加上ls -al命令，这时容器启动并正常执行了ls -al，说明ls -al命令代替了容器中原来的ls -a命令
[root@amumu zzl-dockerfile]# docker run 50e092624b77 ls -al
total 0
drwxr-xr-x. 1 root root 6 May 12 14:44 .
drwxr-xr-x. 1 root root 6 May 12 14:44 ..
-rwxr-xr-x. 1 root root 0 May 12 14:44 .dockerenv
lrwxrwxrwx. 1 root root 7 Nov 3 2020 bin -> usr/bin
drwxr-xr-x. 5 root root 340 May 12 14:44 dev
drwxr-xr-x. 1 root root 66 May 12 14:44 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 Dec 4 17:37 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. 166 root root 0 May 12 14:44 proc
dr-xr-x---. 2 root root 162 Dec 4 17:37 root
drwxr-xr-x. 11 root root 163 Dec 4 17:37 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 9 08:45 sys
drwxrwxrwt. 7 root root 145 Dec 4 17:37 tmp
drwxr-xr-x. 12 root root 144 Dec 4 17:37 usr
drwxr-xr-x. 20 root root 262 Dec 4 17:37 var
[root@amumu zzl-dockerfile]#
# ENTRYPOINT测试
# 1.编写dockerfile-entrypoint 使用ENTRYPOINT命令，在容器运行后自动运行ls -a命令
[root@amumu zzl-dockerfile]# cat dockerfile-entrypoint
FROM centos
MAINTAINER zhuzhonglang<[email protected]>
ENTRYPOINT ["ls","-a"]
# 2.构建镜像
[root@amumu zzl-dockerfile]# docker build -f dockerfile-entrypoint -t dockerentrypoint-test:1.0 .
Sending build context to Docker daemon 4.096kB
Step 1/3 : FROM centos
---> 300e315adb2f
Step 2/3 : MAINTAINER zhuzhonglang<[email protected]>
---> Using cache
---> 313fbe570c8d
Step 3/3 : ENTRYPOINT ["ls","-a"]
---> Running in 5048d75aff02
Removing intermediate container 5048d75aff02
---> 022c0f02e90a
Successfully built 022c0f02e90a
Successfully tagged dockerentrypoint-test:1.0
# 3.运行刚刚创建的镜像，运行镜像后，自动执行了ls -a命令
[root@amumu zzl-dockerfile]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
dockerentrypoint-test 1.0 022c0f02e90a 7 seconds ago 209MB
dockercmd-test 1.0 50e092624b77 14 minutes ago 209MB
mycentos 1.0 ff0a2b5b0669 5 hours ago 291MB
mysql 5.7 87eca374c0ed 3 weeks ago 447MB
nginx latest 62d49f9bab67 4 weeks ago 133MB
centos latest 300e315adb2f 5 months ago 209MB
[root@amumu zzl-dockerfile]# docker run 022c0f02e90a
.
..
.dockerenv
bin
dev
etc
home
lib
lib64
lost+found
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var
# 4.运行镜像，并在镜像后面加上-l ,这时会按照理想中的情况自动执行ls -al命令
[root@amumu zzl-dockerfile]# docker run 022c0f02e90a -l
total 0
drwxr-xr-x. 1 root root 6 May 12 14:54 .
drwxr-xr-x. 1 root root 6 May 12 14:54 ..
-rwxr-xr-x. 1 root root 0 May 12 14:54 .dockerenv
lrwxrwxrwx. 1 root root 7 Nov 3 2020 bin -> usr/bin
drwxr-xr-x. 5 root root 340 May 12 14:54 dev
drwxr-xr-x. 1 root root 66 May 12 14:54 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 Dec 4 17:37 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. 168 root root 0 May 12 14:54 proc
dr-xr-x---. 2 root root 162 Dec 4 17:37 root
drwxr-xr-x. 11 root root 163 Dec 4 17:37 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 9 08:45 sys
drwxrwxrwt. 7 root root 145 Dec 4 17:37 tmp
drwxr-xr-x. 12 root root 144 Dec 4 17:37 usr
drwxr-xr-x. 20 root root 262 Dec 4 17:37 va
#总结：
#CMD:在docker run时添加命令参数，并不会把参数合并到原来CMD对应的命令中，而是把参数作为命令运行了
#ENTRYPOINT:在docker run时添加命令参数，这时会把参数合并到ENTRYPOINT对应的命令中
# CMD和ENTRYPOINT同时存在的时候，CMD不会被执行
[root@amumu zzl-dockerfile]# vi cmd-entrypoint
FROM centos
MAINTAINER zhuzhonglang<[email protected]>
CMD ls -a
ENTRYPOINT echo "hello world"
CMD echo "zhuzhonglnag"
[root@amumu zzl-dockerfile]# docker run 1fb81421a7a6
hello world
[root@amumu zzl-dockerfile]# docker