Reset password in ubuntu

1. Reboot into recovery mode 
2. Select Drop to root shell prompt option
3. In recent versions of Ubuntu, the filesystem is mounted as read-only, so you need to enter the follow command to get it to remount as read-write, which will allow you to make changes:  mount -rw -o remount /
4. If you have forgotten your username as well, type:  ls /home
5. To reset the password, type:  passwd username  ex: passwd meenu
6. You'll then be prompted for a new password. When you type the password you will get no visual response acknowledging your typing. Your password is still being accepted. Just type the password and hit Enter when you're done. You'll be prompted to retype the password. Do so and hit Enter again.
   Now the password should be reset. Type: exit to return to the recovery menu.