NAME

passwd − change login password

SYNOPSIS

passwd [ name ]

DESCRIPTION

This command changes or installs a password associated with the login name.

Ordinary users may change only the password which corresponds to their login name.

passwd prompts ordinary users for their old password, if any.  It then prompts for the new password twice.  The first time the new password is entered passwd checks to see if the old password has “aged” sufficiently.  Password "aging" is the amount of time (usually a certain number of days) that must elapse between password changes.  If “aging” is insufficient the new password is rejected and passwd terminates;  see passwd(4).

Assuming “aging” is sufficient, a check is made to insure that the new password meets construction requirements.  When the new password is entered a second time, the two copies of the new password are compared.  If the two copies are not identical the cycle of prompting for the new password is repeated for at most two more times. 

Passwords must be constructed to meet the following requirements:

Each password must have at least six characters. Only the first eight characters are significant.

Each password must contain at least two alphabetic characters and at least one numeric or special character.  In this case, “alphabetic” means upper and lower case letters. 

Each password must differ from the user’s login name and any reverse or circular shift of that login name. For comparison purposes, an upper case letter and its corresponding lower case letter are equivalent.

New passwords must differ from the old by at least three characters.  For comparison purposes, an upper case letter and its corresponding lower case letter are equivalent. 

One whose effective user ID is zero is called a super-user; see id(1), and su(1). Super-users may change any password; hence, passwd does not prompt super-users for the old password.  Super-users are not forced to comply with password aging and password construction requirements.  A super-user can create a null password by entering a carriage return in response to the prompt for a new password. 

FILES

/etc/passwd

SEE ALSO

chfn(1), chsh(1), id(1M), login(1), su(1M), crypt(3C), passwd(4)

September 02, 1992