View Linux passwd command Manual.


   The example below show how to use man command to view Linux passwd command manual on Linux Fedora operating system.  To display Linux passwd command manual just type in man command and the command name that you want to display the manual page... in this example we want to view Linux passwd command manual... so after the man command we type in passwd (the Linux command name that we want to view the manual).


Linux passwd command manual example:


Open the shell terminal, type in man passwd as example below.

View Linux passwd command Manual

[root@fedora11 ~]# man passwd

PASSWD(1)                       User utilities                       PASSWD(1)



       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:



        # passwd service entry that does strength checking of

        # a proposed password before updating it.


        passwd password requisite \

                    /usr/lib/security/ retry=3

        passwd password required \

                    /usr/lib/security/ use_authtok



       Note, other module-types are not required for this application to function correctly.



       -k     The option, -k, is used to indicate that the update should only be for expired  authentication  tokens  (passwords);  the

              user wishes to keep their non-expired tokens as before.


       -l     This option is used to lock the specified account and it is available to root only. The locking is performed by rendering

              the encrypted password into an invalid string (by prefixing the encrypted string with an !).



              This option is used to indicate that passwd should read the new password from standard input, which can be a pipe.


       -u     This is the reverse of the -l option - it will unlock the account password by removing  the  !  prefix.  This  option  is

              available  to  root  only.  By default passwd will refuse to create a passwordless account (it will not unlock an account

              that has only "!" as a password). The force option -f will override this protection.


       -d     This is a quick way to disable a password for an account. It will set the named account passwordless. Available  to  root



       -n     This  will  set  the minimum password lifetime, in days, if the user's account supports password lifetimes.  Available to

              root only.


       -x     This will set the maximum password lifetime, in days, if the user's account supports password  lifetimes.   Available  to

              root only.


       -w     This  will set the number of days in advance the user will begin receiving warnings that her password will expire, if the

              user's account supports password lifetimes.  Available to root only.


       -i     This will set the number of days which will pass before an expired password for this account will be taken to  mean  that

              the  account  is  inactive  and should be disabled, if the user's account supports password lifetimes.  Available to root



       -S     This will output a short information about the status of the password for a given account. Available to root user only.


Remember the following two principles

       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



       None known.



       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




       Cristian Gafton <>


Red Hat Linux                     Aug 23 2004                        PASSWD(1)



Type in 'q' to exit the manual page.


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