设置密码到期的天数。 
用户必须在天内更改密码。 
此设置仅影响创建用户，而不会影响现有用户。 
如果设置为现有用户，请运行命令“chage -M（days）（user）”。

PASS_MAX_DAYS   60         # 密码到期时间
PASS_MIN_DAYS   3          # 初始密码更改时间
PASS_MIN_LEN    8          # 密码最小长度
PASS_WARN_AGE   7          # 密码过期提示时间

 [root@linuxprobe~]# vi /etc/pam.d/system-auth
# near line 15: prohibit to use the same password for 5 generation in past

password     sufficient     pam_unix.so sha512 shadow nullok try_first_pass use_authtok remember=5

 # set 8 for minimum password length

[root@linuxprobe~]# authconfig --passminlen=8 --update
# the parameter is set in a config below

[root@linuxprobe~]# grep "^minlen" /etc/security/pwquality.conf
minlen = 8 

# 在新密码中设置同一类的允许连续字符的最大数目
 # set 4 for maximum number of allowed consecutive characters of the same class

[root@linuxprobe~]# authconfig --passmaxclassrepeat=4 --update
# the parameter is set in a config below

[root@linuxprobe~]# grep "^maxclassrepeat" /etc/security/pwquality.conf
maxclassrepeat = 4 

# 在新密码中至少需要一个小写字符。
 [root@linuxprobe~]# authconfig --enablereqlower --update
# the parameter is set in a config below
# (if you'd like to edit the value, edit it with vi and others)

[root@linuxprobe~]# grep "^lcredit" /etc/security/pwquality.conf
lcredit = -1 

# 在新密码中至少需要一个大写字符
 [root@linuxprobe~]# authconfig --enablerequpper --update
# the parameter is set in a config below

# (if you'd like to edit the value, edit it with vi and others)
[root@linuxprobe~]# grep "^ucredit" /etc/security/pwquality.conf
ucredit = -1 

# 在新密码中至少需要一个数字
 [root@linuxprobe~]# authconfig --enablereqdigit --update
# the parameter is set in a config below

# (if you'd like to edit the value, edit it with vi and others)
[root@linuxprobe~]# grep "^dcredit" /etc/security/pwquality.conf
dcredit = -1 

# 密码包括至少一个特殊字符
 [root@linuxprobe~]# authconfig --enablereqother --update
# the parameter is set in a config below

# (if you'd like to edit the value, edit it with vi and others)
[root@linuxprobe~]# grep "^ocredit" /etc/security/pwquality.conf
ocredit = -1 

# 在新密码中设置单调字符序列的最大长度。 （ex⇒'12345'，'fedcb'）
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
maxsequence = 3 

# 设置新密码中不能出现在旧密码中的字符数
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
difok = 5 

# 检查来自用户passwd条目的GECOS字段的长度超过3个字符的字是否包含在新密码中。
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
gecoscheck = 1 

# 设置不能包含在密码中的Ssace分隔的单词列表
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
badwords = denywords1 denywords2 denywords3 

# 为新密码设置hash / crypt算法。 （默认为sha512）
# show current algorithm

[root@linuxprobe~]# authconfig --test | grep hashing

password hashing algorithm is md5
# chnage algorithm to sha512

[root@linuxprobe~]# authconfig --passalgo=sha512 --update
[root@linuxprobe~]# authconfig --test | grep hashing
password hashing algorithm is sha512