Password policy is a critical factor in PC security since user passwords are too often the main purpose behind computer system security break. The secret word approach expected to characterize the minimum length of a password, the number of days a password is valid, the strength of a passowrd, and a notice period to alert people that their password is going to expire.
Configure Password Policy – Aging and Length
The maximum number of days allowed, minimum number of days allowed, and number of warning days before the password expires refers to password aging, same as the number of characters needed to have for the password to be allowed refers to password length. This setting impact only when creating a user, not impact to exisiting users.
# vim /etc/login.defs
# 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.