A normal user may only change the password for his/her own account, the super user may change the password for any account. The administrator of a group may change the password for the group. passwd also changes account information, such as the full name of the user, user’s login shell, or password expiry date and interval.
Type passwd command as follows:
$ passwd
The user is first prompted for his/her old password, if one is present. This password is then encrypted and compared against the stored password. The user has only one chance to enter the correct password. The super user is permitted to bypass this step so that forgotten passwords may be changed.
A new password is tested for complexity. As a general guideline, passwords should consist of 6 to 8 characters including one or more from each of following sets:
– Lower case alphabetics
– Upper case alphabetics
– Digits 0 thru 9
– Punctuation marks