how to change user password without current password.

If you dont know the current user password ,Then only root user can change the password .

login as root user  and then try as below steps .

syntax :-  passwd <username>

example :- 

[root@tstvm ~]# passwd sai

Changing password for user sai.

New password:

Retype new password:

passwd: all authentication tokens updated successfully.

[root@tstvm ~]#

BAD PASSWORD: it is based on a dictionary word