The -max argument to the passwd command sets an age limit for the current password. In other words, it specifies the number of days that a password remains valid. After that number of days, a new password must be chosen by the user. Once the maximum number of days have passed, the next time the user tries to login with the old password a Your password has been expired for too long message is displayed and the user is forced to choose a new password in order to finish logging in to the system.
The max argument uses the following format:
passwd -x max username
username is the login ID of the user
max is one of the following values:
Greater than zero. Any number greater than zero sets that number of days before the password must be changed.
Zero (0). A value of zero (0) forces the user to change passwords the next time the user logs in, and it then turns off password aging.
Minus one (-1). A value of minus one (-1) turns off password aging. In other words, entering passwd -x -1 username cancels any previous password aging applied to that user.
For example, to force the user schweik to change passwords every 45 days, you would type the command:
station1% passwd -x 45 schweik