exp:
[root@centos6 ~]# chage -d 0 user1
[root@centos6 ~]# chage -m 0 -M 42 -W 14 -I 7 user1
[root@centos6 ~]# chage -E 2018-09-10 user1
[root@centos6 ~]# chage -l user1
Last password change                                    : password must be changed
Password expires                                        : password must be changed
Password inactive                                       : password must be changed
Account expires                                         : Sep 10, 2018
Minimum number of days between password change          : 0
Maximum number of days between password change          : 42
Number of days of warning before password expires       : 14

[root@centos6 ~]# cat /etc/passwd
root:x:0:0:dongfei,it,11101,131312221:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin

[root@centos6 ~]# cat /etc/group
root:x:0:gentoo,user11
bin:x:1:bin,daemon,gentoo,user11

[root@centos6 ~]# cat /etc/shadow
root:$6$9MvILiAieGOcghCi$2/ZmaouQQZLQPJNPlaVNUmsAijd34JJIPnR4OPiTTyTTo8bkdPAoFDvo5V/Lni1i1hiAyLdRe7tylR2PfZNsM.:17622:0:99999:7:::
bin:*:17622:0:99999:7:::

[root@centos6 ~]# cat /etc/gshadow
root:::gentoo,user11
bin:::bin,daemon,gentoo,user11

[root@centos6 ~]# ls -a /etc/skel/
.  ..  .bash_logout  .bash_profile  .bashrc  .gnome2  .mozilla

[root@centos6 ~]# cat /etc/default/useradd
# useradd defaults file
GROUP=100　　　　　　　　　　 #users组ID
HOME=/home　　　　　　　　　  #家目录位置
INACTIVE=-1　　　　　　　　   #非活动时间不限定
EXPIRE=
SHELL=/bin/bash　　　　　 　 #创建用户时默认shell
SKEL=/etc/skel　　　　　　　　#家目录模板目录
CREATE_MAIL_SPOOL=yes　　　　#是否创建邮箱

[root@centos6 ~]# cat /etc/login.defs 
#
# Please note that the parameters in this configuration file control the
# behavior of the tools from the shadow-utils component. None of these
# tools uses the PAM mechanism, and the utilities that use PAM (such as the
# passwd command) should therefore be configured elsewhere. Refer to
# /etc/pam.d/system-auth for more information.
#

# *REQUIRED*
#   Directory where mailboxes reside, _or_ name of file, relative to the
#   home directory.  If you _do_ define both, MAIL_DIR takes precedence.
#   QMAIL_DIR is for Qmail
#
#QMAIL_DIR      Maildir
MAIL_DIR        /var/spool/mail　　　　　　#创建邮箱目录
#MAIL_FILE      .mail

# Password aging controls:
#
#       PASS_MAX_DAYS   Maximum number of days a password may be used.
#       PASS_MIN_DAYS   Minimum number of days allowed between password changes.
#       PASS_MIN_LEN    Minimum acceptable password length.
#       PASS_WARN_AGE   Number of days warning given before a password expires.
#
PASS_MAX_DAYS   99999　　　　　　　　　　　　#密码最大有效期，300年
PASS_MIN_DAYS   0　　　　　　　　　　　　　　#密码最短有效期
PASS_MIN_LEN    5　　　　　　　　　　　　　　#密码最短长度
PASS_WARN_AGE   7　　　　　　　　　　　　　　#密码警告期限

#
# Min/max values for automatic uid selection in useradd
#
UID_MIN                   500　　　　　　　#登录用户的UID范围 500-60000
UID_MAX                 60000

#
# Min/max values for automatic gid selection in groupadd
#
GID_MIN                   500　　　　　　　　#登录用户的GID范围 500-60000
GID_MAX                 60000

#
# If defined, this command is run when removing a user.
# It should remove any at/cron/print jobs etc. owned by
# the user to be removed (passed as the first argument).
#
#USERDEL_CMD    /usr/sbin/userdel_local

#
# If useradd should create home directories for users by default
# On RH systems, we do. This option is overridden with the -m flag on
# useradd command line.
#
CREATE_HOME     yes　　　　　　　　　　#是否创建家目录

# The permission mask is initialized to this value. If not specified, 
# the permission mask will be initialized to 022.
UMASK           077

# This enables userdel to remove user groups if no members exist.
#
USERGROUPS_ENAB yes

# Use SHA512 to encrypt password.
ENCRYPT_METHOD SHA512　　　　　　　　　#默认加密算法

MD5_CRYPT_ENAB no