Provided by:
passwd_4.1.4.2-1ubuntu3_i386 
crypt(3).
crypt(3), for instance ! or *, the user will not be able to use a unix
date of last password change
The date of the last password change, expressed as the number of days
since Jan 1, 1970.
The value 0 has a special meaning, which is that the user should change
her pasword the next time she will log in the system.
An empty field means that password aging features are disabled.
minimum password age
The minimum password age is the number of days the user will have to wait
before she will be allowed to change her password again.
An empty field and value 0 mean that there are no minimum password age.
maximum password age
The maximum password age is the number of days after which the user will
have to change her password.
After this number of days is elapsed, the password may still be valid. The
user should be asked to change her password the next time she will log in.
An empty field means that there are no maximum password age, no password
warning period, and no password inactivity period (see below).
If the maximum password age is lower than the minimum password age, the
user cannot change her password.
password warning period
The number of days before a password is going to expire (see the maximum
password age above) during which the user should be warned.
An empty field and value 0 mean that there are no password warning period.
password inactivity period
The number of days after a password has expired (see the maximum password
age above) during which the password should still be accepted (and the
user should update her password during the next login).
After expiration of the password and this expiration period is elapsed, no
login is possible using the current users password. The user should
contact her administrator.
An empty field means that there are no enforcement of an inactivity
period.
account expiration date
The date of expiration of the account, expressed as the number of days
since Jan 1, 1970.
Note that an account expiration differs from a password expiration. In
case of an acount expiration, the user shall not be allowed to login. In
case of a password expiration, the user is not allowed to login using her
password.
An empty field means that the account will never expire.
The value 0 should not be used as it is interpreted as either an account
with no expiration, or as an expiration on Jan 1, 1970.
reserved field
This field is reserved for future use.
/etc/passwd
/etc/shadow
/etc/shadow-
Backup file for /etc/shadow.
Note that this file is used by the tools of the shadow toolsuite,
but not by all user and password management tools.
chage(1), login(1), passwd(1), passwd(5), pwck(8), pwconv(8),
pwunconv(8), su(1), sulogin(8).
09/03/2010 shadow(5)