Module 100 passwd | Illustrated Unix System V/Bsd

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Module 100
passwd

DESCRIPTION

The external passwd command allows you to create or change the password associated with your user name . The super-user (system administrator) can change any user s password and is not prompted for the old password. As a user you can only change your password.

COMMAND FORMAT

Following is the general format for the passwd command.

 passwd [ user_name ]      passwd [ -df ][ -n min ][ -x max ][ -w warn ]user_name      passwd [ -fl ][ -n min ][ -x max ][ -w warn ]user_name      passwd -s[-a ]      passwd -s[ user_name ]

BSD (Berkeley)

	`passwd [ -fs ][ user_name ]`

Options

The following list describes the options used to control how passwd functions.

-d	Deletes the password for user_name . The user_name will not be prompted for a password.
-f	Force the password to expire. The user_name is forced to enter a new password at the next login.
-l	Lock the password entry for user_name . No changes may be made.
-n min	Set the minimum number of days between password changes.
-s	Display (show) password attributes for user user_name . If no user_name is specified, your login user_name is used. The format of the information is,

		`user-name status mm/dd/yy min max warn`
	or, if no password aging information is present
		`user-name status`
	where

		user_name	The login ID of a user
		status	The password status

		PS	Passworded
		LK	Locked
		NP	No password

	mm/dd/yy	The date the password was last changed
	min	The minimum number of days between password changes. The label MINWEEKS specifies the default. It is located in the /etc/default/passwd file and is set to NULL. If min is greater than max , the user may not change the password. Always use with the -x option.
	max	The maximum number of days the password is valid. The user is forced to change the password every max days. The label MAXWEEKS specifies the default. It is located in the /etc/default/passwd file and is set to NULL. If max is set to -1 then aging is turned off. If it is set to 0 then user_name is forced to change the password at the next login and aging is turned off.
	warn	The number of days before the password expires , based on max , that the user_name will be warned .
-a	Display password attributes for all entries in the password file.
-w warn	Set the number of days before the password expires to notify the user_name .
-x max	Set the maximum number of days the password is valid.

BSD(Berkeley)

-f	Allows you to change the information field of the /etc/passwd file for your login. Refer to chfn in Module 15 for further information.
-s	Allows you to change the login shell in the /etc/passwd file for your login.

Arguments

The following list describes the argument that may be passed to the passwd command.

user_name

A valid user name in the /etc/passwd file. The user name is the first column ( colon -separated columns ) of the /etc/passwd file. Only the super-user can change another user s password.

FURTHER DISCUSSION

The use of passwords and their implementation is highly dependent upon your company s security policy and your system administrator. Some system administrators don t require passwords, while others require passwords, perform full accounting on every user, and implement password aging. Check with you system administrator for the requirements placed on your account.

PASSWORD AGING

The passwd command is capable of checking the elapsed time since the password was last changed, referred to as password aging . If the elapsed time is sufficient, then the user is allowed to change the password. Password aging also requires that a user must change passwords after a specified amount of time. The system administrator decides if password aging is activated and how long each password is aged.

BSD (Berkeley)

Most BSD based systems do not provide password aging. You should check your reference manual for specific password implementations on your system.

PASSWORD REQUIREMENTS

The following is a list of requirements that a password must meet before passwd will allow it as your password.

1. Must contain six characters. Only the first 8 characters are significant. The label PASSLEN specifies the maximum length for a password. It is in the file /etc/default/passwd.

2. Must contain 2 alphabetic characters (upper or lowercase letters ) and at least one special character or number.

3. Must not be any circular shift combination or reversal of the user name. For example, if your user name is bill, your password could not be lbil, llbi, illb, or llib, blli, ibll, libl.

4. New passwords must have at least 3 characters that differ from the old password.

BSD (Berkeley)

Berkeley is much more lenient about passwords. The following requirements must be met for a valid password.
	1. Must contain four characters. Upper and lowercase.
	2. Must contain six characters if only monocase.

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