Rules for changing passwords for user accounts

1. A normal user may only change the password for his/her own account.
2. The superuser (root user) may change the password for any account or specific account.
3. The passwd command also changes the account or associated password validity period.

First, login as the root user. Use sudo -s or su - command to login as root. To change password of specific user account, use the following syntax:

passwd userNameHere

To change the password for user called vivek, enter:
# passwd vivek
Sample outputs:

vivek P 05/05/2012 0 99999 7 -1

The status information consists of 7 fields as follows:

1. vivek : Account login name (username)
2. P : This field indicates if the user account has a locked password (L), has no password (NP), or has a usable password (P)
3. 05/05/2012 : Date of the last password change.
4. 0 : Password expiry minimum age
5. 99999 : Password expiry maximum age.
6. 7 : Password expiry warning period.
7. -1 : Inactivity period for the password (see chage command for more information).

To get more info about password aging for a specific user called vivek, enter:
# chage -l vivek