設(shè)置密碼到期的天數(shù)。 
用戶必須在天內(nèi)更改密碼。 
此設(shè)置僅影響創(chuàng)建用戶，而不會(huì)影響現(xiàn)有用戶。 
如果設(shè)置為現(xiàn)有用戶，請(qǐng)運(yùn)行命令“chage -M（days）（user）”。

PASS_MAX_DAYS   60         # 密碼到期時(shí)間
PASS_MIN_DAYS   3          # 初始密碼更改時(shí)間
PASS_MIN_LEN    8          # 密碼最小長(zhǎng)度
PASS_WARN_AGE   7          # 密碼過(guò)期提示時(shí)間

 [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 

# 在新密碼中設(shè)置同一類的允許連續(xù)字符的最大數(shù)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 

# 在新密碼中至少需要一個(gè)小寫(xiě)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 

# 在新密碼中至少需要一個(gè)大寫(xiě)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 

# 在新密碼中至少需要一個(gè)數(shù)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 

# 密碼包括至少一個(gè)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 

# 在新密碼中設(shè)置單調(diào)字符序列的最大長(zhǎng)度。 （ex⇒'12345'，'fedcb'）
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
maxsequence = 3 

# 設(shè)置新密碼中不能出現(xiàn)在舊密碼中的字符數(shù)
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
difok = 5 

# 檢查來(lái)自用戶passwd條目的GECOS字段的長(zhǎng)度超過(guò)3個(gè)字符的字是否包含在新密碼中。
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
gecoscheck = 1 

# 設(shè)置不能包含在密碼中的Ssace分隔的單詞列表
 [root@linuxprobe~]# vi /etc/security/pwquality.conf
# add to the end
badwords = denywords1 denywords2 denywords3 

# 為新密碼設(shè)置hash / crypt算法。 （默認(rèn)為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