Password

Access to a UNIX system historically was granted by means of passwords. These consisted of all keys on a typical US keyboard and were at first limited in length. Implementations exist for one time passwords also called skey. Another method for access to UNIX systems are Kerberos passwords. A Unix system is not limited to it's own password database to grant access to users, alternative are NIS or using PAM for a variety of password implementations.

How to change a password

To change your password type passwd and the system will ask you to enter your current password as a security measure, unless you are root.