Passwd
passwd is a tool on most Unix and Linux systems used to change a user's password.
passwd generally works by manipulating the local username and password storage file (/etc/passwd, and on some systems /etc/shadow where shadow passwords are in use), which means the changed password applies only for the computer on which the command was run. For environments which allow a single password to be used for the same user on a number of networked machines (such as Sun's NIS) the equivalent command is yppasswd. Some versions of passwd warn the user if they choose a weak password (such as one less than six characters long).
