When adding users, which files will be modified?

• /etc/passwd stores user information
• /etc/group stores user group information
• /etc/shadow store user password
• /etc/gshadow store user group password

[root@localhost ~]# cat /etc/default/useradd
# useradd defaults file
GROUP=100             #It depends on the configuration of Usergroups ﹣ enab in / etc/login.defs. If it is no, it is empty here
HOME=/home            #User home directory location
INACTIVE=-1           #Do you want to enable account expiration and suspension? - 1 is not enabled
EXPIRE=               #Account end date, null value is not enabled
SHELL=/bin/bash       #Default shell
SKEL=/etc/skel        #Home directory default template
CREATE_MAIL_SPOOL=yes #Create user mailbox or not

New user's home directory template / etc/skel/

[root@localhost ~]# ls /etc/skel/ -al
total 20
drwxr-xr-x.  2 root root 4096 Jun  9 16:51 .
drwxr-xr-x. 79 root root 4096 Jul  6 19:04 ..
-rw-r--r--.  1 root root   18 Mar 23 08:15 .bash_logout
-rw-r--r--.  1 root root  176 Mar 23 08:15 .bash_profile #environment variable
-rw-r--r--.  1 root root  124 Mar 23 08:15 .bashrc #alias

Case - the command line prompt is: - bash-4.1$

Reason:
Use rm command to delete. Bash? Profile and. bashrc in zzz home directory by mistake
Phenomenon:

[root@localhost ~]# su - zzz
-bash-4.1$

Solution:

Copying files from a home directory template

-bash-4.1$ cp /etc/skel/.bash* ~
-bash-4.1$ logout
[root@localhost ~]# su - zzz
[zzz@localhost ~]$

Specify new user password rule / etc/login.defs

[root@localhost ~]# egrep -v '^#|^$' /etc/login.defs
MAIL_DIR        /var/spool/mail
PASS_MAX_DAYS   99999          #Maximum password life
PASS_MIN_DAYS   0              #Minimum password life (change cycle)
PASS_MIN_LEN    5              #Minimum password length
PASS_WARN_AGE   7              #Warning days in advance of password failure
UID_MIN         1000
UID_MAX         60000
SYS_UID_MIN     201
SYS_UID_MAX     999
GID_MIN         1000
GID_MAX         60000
SYS_GID_MIN     201
SYS_GID_MAX     999
CREATE_HOME     yes
UMASK           077            #Default permission mask
USERGROUPS_ENAB yes
ENCRYPT_METHOD  SHA512