passwd command help
passwd - update a user's authentication tokens(s)
passwd [-k] [-l] [-u [-f]] [-d] [-S] [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 \
passwd password required \
Note, other module-types are not required for this appli
cation 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
unlock the account password by removing the ! pre
fix. 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 password
less. Available to root only.
-S This will output a short information about the sta
tus 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 any
where, 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 any
one 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, par
ent, 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 environ
ment. Don't use a birthday or a simple pattern
(such as backwards, followed by a digit, or pre
ceded by a digit. Instead, use a mixture of upper
and lower case letters, as well as digits or punc
tuation. 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
These principles are partially enforced by the system, but
only partly so. Vigilence on your part will make the sys
tem 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
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
Cristian Gafton <email@example.com>
Comments - most recent first
(Please feel free to answer questions posted by others!)
(23 Sep 2012, 08:06
hi Vishal P
Sudo stand for "super user do"..
its work as apply as administer like in windows..it give u temporally
accessibility on the system for installing application in linux system.
(23 Mar 2012, 22:27
How to verify when root password was changed in GNU Linux. I want to know
in past 6 month how many times it was changed and when was it changed.
(17 Jan 2012, 23:15
Im trying to set the same password for multiple users.. im using sudo
passwd ace (ace being the username) and then im asked for the password..
but how do i add multiple users int hat same line of code?.. any help would
(21 Sep 2011, 09:04
How can I give password when I create a new user using "adduser" command
(07 Jun 2011, 02:07
What is SUDO in ubantu ?
(24 Feb 2011, 03:51
i want to change my password in linux, but i forgot the old one. so how can
I change my password another way?
(27 Dec 2010, 17:57
i would like to change my password from the one i have now how do i do that
(19 Dec 2010, 23:39
how to change my password?
(12 Dec 2010, 12:49
@zaralee - Logging in as root is the same as logging in as any other user.
"root" is the username, there's nothing special about it, in terms of
(07 Dec 2010, 09:56
how do you log in as root? i dont know what this means. Please explain.
(03 Aug 2010, 15:16
@Sarah - You'll need to login as root, or have someone with root privileges
issue the passwd command.
(03 Aug 2010, 14:57
I want to change my password but i forgot the old one. so how can I change
my password another way?
(15 Jul 2010, 14:55
We adopted this Knoppix Linux, which is ok, and it has this CUPS software
which governs print jobs. It wants the system username and password(root),
in order to just cancel a printjob that is stuck. Would it also be possible
to use a pw from the 'console'? Thankyou for this course, it is realy fine.
(05 Jun 2010, 11:09
i need to change my e-mail password.
(31 May 2010, 10:07
will these stop me from down loading,and others that use my computer, i
dont no one to down load anything but me.
(28 May 2010, 23:57
how can not password skip
(28 May 2010, 20:59
(28 May 2010, 20:51
(28 May 2010, 20:39
iwant to change this because my friends have it.
(28 May 2010, 10:27
@nuri, to change ur password, u have to login by root , the superuser and
then put the passwd command for the user ,
it will change the password,
Gideon C. Gucilatar
(07 May 2010, 22:02
How to change my password?
(04 May 2010, 05:37
I want to can my password because all my friends know the password so,how
can i change my password.
I welcome your comments. However... I am puzzled by many people
who say "Please send me the Linux tutorial." This website *is* your Linux Tutorial! Read everything here, learn
all you can, ask questions if you like. But don't ask me to send what you already have. :-)
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by Bob Rankin
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