passwd - update a user’s authentication tokens(s)
passwd [-k] [-l] [-u [-f]] [-d] [-n mindays] [-x maxdays] [-w warndays] [-i inactivedays] [-S] [--stdin] [username]
Passwd is used to update a user’s authentication token(s).
Passwd is configured to work through the Linux-PAM API. Essentially, it initializes itself as a “passwd” service with Linux-PAM and utilizes configured password modules to authenticate and then update a user’s password.
A simple entry in the Linux-PAM configuration file for this service would be:
Note, other module-types are not required for this application to function correctly.
Protect your password.
Don’t write down your password - memorize it. In particular, don’t write it down and leave it anywhere, and don’t place it in an unencrypted file! Use unrelated passwords for systems controlled by different organizations. Don’t give or share your password, in particular to someone claiming to be from computer support or a vendor. Don’t let anyone watch you enter your password. Don’t enter your password to a computer you don’t trust or if things Use the password for a limited time and change it periodically.
Choose a hard-to-guess password.
passwd will try to prevent you from choosing a really bad password, but it isn’t foolproof; create your password wisely. Don’t use something you’d find in a dictionary (in any language or jargon). Don’t use a name (including that of a spouse, parent, child, pet, fantasy character, famous person, and location) or any variation of your personal or account name. Don’t use accessible information about you (such as your phone number, license plate, or social security number) or your environment. Don’t use a birthday or a simple pattern (such as backwards, followed by a digit, or preceded by a digit. Instead, use a mixture of upper and lower case letters, as well as digits or punctuation. When choosing a new password, make sure it’s unrelated to any previous password. Use long passwords (say 8 characters long). You might use a word pair with punctuation inserted, a passphrase (an understandable sequence of words), or the first letter of each word in a passphrase.
These principles are partially enforced by the system, but only partly so. Vigilence on your part will make the system much more secure.
On successful completion of its task, passwd will complete with exit code 0. An exit code of 1 indicates an error occurred. Textual errors are written to the standard error stream.
Linux-PAM (Pluggable Authentication modules for Linux). Note, if your distribution of Linux-PAM conforms to the Linux Filesystem Standard, you may find the modules in /lib/security/ instead of /usr/lib/security/, as indicated in the example.
/etc/pam.d/passwd - the Linux-PAM configuration file
pam(8) , and pam_chauthok(2) .
For more complete information on how to configure this application with Linux-PAM, see the Linux-PAM System Administrators’ Guide at <http://parc.power.net/morgan/Linux-PAM/index.html>
Cristian Gafton <email@example.com>
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