1PASSWD(1) User utilities PASSWD(1)
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6 passwd - update user's authentication tokens
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10 passwd [-k] [-l] [-u [-f]] [-d] [-e] [-n mindays] [-x maxdays] [-w
11 warndays] [-i inactivedays] [-S] [--stdin] [username]
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16 The passwd utility is used to update user's authentication token(s).
17 This task is achieved through calls to the Linux-PAM and Libuser API.
19 Essentially, it initializes itself as a "passwd" service with Linux-PAM
20 and utilizes configured password modules to authenticate and then
21 update a user's password.
22 A simple entry in the global Linux-PAM configuration file for this ser‐
25 vice would be:
26 #
28 # passwd service entry that does strength checking of
29 # a proposed password before updating it.
30 #
31 passwd password requisite pam_cracklib.so retry=3
32 passwd password required pam_unix.so use_authtok
33 #
34 Note, other module types are not required for this application to func‐
37 tion correctly.
38
41 -k The option -k, is used to indicate that the update should only
42 be for expired authentication tokens (passwords); the user
43 wishes to keep their non-expired tokens as before.
44 -l This option is used to lock the specified account and it is
47 available to root only. The locking is performed by rendering
48 the encrypted password into an invalid string (by prefixing the
49 encrypted string with an !).
50 --stdin
53 This option is used to indicate that passwd should read the new
54 password from standard input, which can be a pipe.
55 -u This is the reverse of the -l option - it will unlock the
58 account password by removing the ! prefix. This option is avail‐
59 able to root only. By default passwd will refuse to create a
60 passwordless account (it will not unlock an account that has
61 only "!" as a password). The force option -f will override this
62 protection.
63 -d This is a quick way to delete a password for an account. It will
66 set the named account passwordless. Available to root only.
67 -e This is a quick way to expire a password for an account. The
70 user will be forced to change the password during the next login
71 attempt. Available to root only.
72 -n This will set the minimum password lifetime, in days, if the
75 user's account supports password lifetimes. Available to root
76 only.
77 -x This will set the maximum password lifetime, in days, if the
80 user's account supports password lifetimes. Available to root
81 only.
82 -w This will set the number of days in advance the user will begin
85 receiving warnings that her password will expire, if the user's
86 account supports password lifetimes. Available to root only.
87 -i This will set the number of days which will pass before an
90 expired password for this account will be taken to mean that the
91 account is inactive and should be disabled, if the user's
92 account supports password lifetimes. Available to root only.
93 -S This will output a short information about the status of the
96 password for a given account. Available to root user only.
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100 Protect your password.
101 Don't write down your password - memorize it. In particular,
102 don't write it down and leave it anywhere, and don't place it in
103 an unencrypted file! Use unrelated passwords for systems con‐
104 trolled by different organizations. Don't give or share your
105 password, in particular to someone claiming to be from computer
106 support or a vendor. Don't let anyone watch you enter your
107 password. Don't enter your password to a computer you don't
108 trust or if things Use the password for a limited time and
109 change it periodically.
110 Choose a hard-to-guess password.
113 passwd through the calls to the pam_cracklib PAM module will try
114 to prevent you from choosing a really bad password, but it isn't
115 foolproof; create your password wisely. Don't use something
116 you'd find in a dictionary (in any language or jargon). Don't
117 use a name (including that of a spouse, parent, child, pet, fan‐
118 tasy character, famous person, and location) or any variation of
119 your personal or account name. Don't use accessible information
120 about you (such as your phone number, license plate, or social
121 security number) or your environment. Don't use a birthday or a
122 simple pattern (such as backwards, followed by a digit, or pre‐
123 ceded by a digit. Instead, use a mixture of upper and lower case
124 letters, as well as digits or punctuation. When choosing a new
125 password, make sure it's unrelated to any previous password. Use
126 long passwords (say at least 8 characters long). You might use
127 a word pair with punctuation inserted, a passphrase (an under‐
128 standable sequence of words), or the first letter of each word
129 in a passphrase.
130 These principles are partially enforced by the system, but only partly
134 so. Vigilence on your part will make the system much more secure.
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138 On successful completion of its task, passwd will complete with exit
139 code 0. An exit code of 1 indicates an error occurred. Textual errors
140 are written to the standard error stream.
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144 Linux-PAM (Pluggable Authentication modules for Linux).
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148 /etc/pam.d/passwd - the Linux-PAM configuration file
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152 None known.
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156 pam(8), pam.d(5), libuser.conf(5), and pam_chauthtok(3).
157 For more complete information on how to configure this application with
160 Linux-PAM, see the Linux-PAM System Administrators' Guide.
161
164 Cristian Gafton <gafton@redhat.com>
165GNU/Linux Jan 26 2012 PASSWD(1)