.TH PASSWD 1 .SH NAMEpasswd \- change login password.SH SYNOPSIS.B passwd[ name ].SH DESCRIPTIONThis command changes (or installs) a passwordassociated with the user.IR name(your own name by default)..PPThe program prompts for the old password and then for the new one.The caller must supply both.The new password must be typed twice, to forestall mistakes..PPNew passwords must be at least four characters long if they usea sufficiently rich alphabet and at least six characters longif monocase.These rules are relaxed if you are insistent enough..PPOnly the owner of the name or the super-user may change a password;the owner must prove he knows the old password..SH FILES/etc/passwd.SH "SEE ALSO"login(1), passwd(5), crypt(3).brRobert Morris and Ken Thompson,.I Password Security: A Case History