docker run -ti -v my_passwd:/etc/passwd -v my_shadow:/etc/shadow --rm centos
[root@681a5489f3b0 /]# useradd test # does not work !?
useradd: failure while writing changes to /etc/passwd
[root@681a5489f3b0 /]# ll /etc/passwd /etc/shadow # permission check
-rw-r--r-- 1 root root 157 Oct 8 10:17 /etc/passwd
-rw-r----- 1 root root 100 Oct 7 18:02 /etc/shadow
使用passwd时出现类似问题：
[root@681a5489f3b0 /]# passwd test
Changing password for user test.
New password:
BAD PASSWORD: The password is shorter than 8 characters
Retype new password:
passwd: Authentication token manipulation …