1PASSWD(1) User utilities PASSWD(1)
2
6 passwd - update a user's authentication tokens(s)
7
10 passwd [-k] [-l] [-u [-f]] [-d] [-n mindays] [-x maxdays] [-w warndays]
11 [-i inactivedays] [-S] [--stdin] [username]
12
16 Passwd is used to update a user's authentication token(s).
17 Passwd is configured to work through the Linux-PAM API. Essentially,
19 it initializes itself as a "passwd" service with Linux-PAM and utilizes
20 configured password modules to authenticate and then update a user's
21 password.
22 A simple entry in the Linux-PAM configuration file for this service
25 would be:
26 #
28 # passwd service entry that does strength checking of
29 # a proposed password before updating it.
30 #
31 passwd password requisite \
32 /usr/lib/security/pam_cracklib.so retry=3
33 passwd password required \
34 /usr/lib/security/pam_unix.so use_authtok
35 #
36 Note, other module-types are not required for this application to func‐
39 tion correctly.
40
43 -k The option, -k, is used to indicate that the update should only
44 be for expired authentication tokens (passwords); the user
45 wishes to keep their non-expired tokens as before.
46 -l This option is used to lock the specified account and it is
49 available to root only. The locking is performed by rendering
50 the encrypted password into an invalid string (by prefixing the
51 encrypted string with an !).
52 --stdin
55 This option is used to indicate that passwd should read the new
56 password from standard input, which can be a pipe.
57 -u This is the reverse of the -l option - it will unlock the
60 account password by removing the ! prefix. This option is avail‐
61 able to root only. By default passwd will refuse to create a
62 passwordless account (it will not unlock an account that has
63 only "!" as a password). The force option -f will override this
64 protection.
65 -d This is a quick way to disable a password for an account. It
68 will set the named account passwordless. Available to root only.
69 -n This will set the minimum password lifetime, in days, if the
72 user's account supports password lifetimes. Available to root
73 only.
74 -x This will set the maximum password lifetime, in days, if the
77 user's account supports password lifetimes. Available to root
78 only.
79 -w This will set the number of days in advance the user will begin
82 receiving warnings that her password will expire, if the user's
83 account supports password lifetimes. Available to root only.
84 -i This will set the number of days which will pass before an
87 expired password for this account will be taken to mean that the
88 account is inactive and should be disabled, if the user's
89 account supports password lifetimes. Available to root only.
90 -S This will output a short information about the status of the
93 password for a given account. Available to root user only.
94
97 Protect your password.
98 Don't write down your password - memorize it. In particular,
99 don't write it down and leave it anywhere, and don't place it in
100 an unencrypted file! Use unrelated passwords for systems con‐
101 trolled by different organizations. Don't give or share your
102 password, in particular to someone claiming to be from computer
103 support or a vendor. Don't let anyone watch you enter your
104 password. Don't enter your password to a computer you don't
105 trust or if things Use the password for a limited time and
106 change it periodically.
107 Choose a hard-to-guess password.
110 passwd will try to prevent you from choosing a really bad pass‐
111 word, but it isn't foolproof; create your password wisely.
112 Don't use something you'd find in a dictionary (in any language
113 or jargon). Don't use a name (including that of a spouse, par‐
114 ent, child, pet, fantasy character, famous person, and location)
115 or any variation of your personal or account name. Don't use
116 accessible information about you (such as your phone number,
117 license plate, or social security number) or your environment.
118 Don't use a birthday or a simple pattern (such as backwards,
119 followed by a digit, or preceded by a digit. Instead, use a mix‐
120 ture of upper and lower case letters, as well as digits or punc‐
121 tuation. When choosing a new password, make sure it's unrelated
122 to any previous password. Use long passwords (say 8 characters
123 long). You might use a word pair with punctuation inserted, a
124 passphrase (an understandable sequence of words), or the first
125 letter of each word in a passphrase.
126 These principles are partially enforced by the system, but only partly
130 so. Vigilence on your part will make the system much more secure.
131
134 On successful completion of its task, passwd will complete with exit
135 code 0. An exit code of 1 indicates an error occurred. Textual errors
136 are written to the standard error stream.
137
140 Linux-PAM (Pluggable Authentication modules for Linux).
141 Note, if your distribution of Linux-PAM conforms to the Linux Filesys‐
142 tem Standard, you may find the modules in /lib/security/ instead of
143 /usr/lib/security/, as indicated in the example.
144
147 /etc/pam.d/passwd - the Linux-PAM configuration file
148
151 None known.
152
155 pam(8), and pam_chauthok(2).
156 For more complete information on how to configure this application with
159 Linux-PAM, see the Linux-PAM System Administrators' Guide at
160 /usr/share/doc/pam...
161
164 Cristian Gafton <gafton@redhat.com>
165Red Hat Linux Aug 23 2004 PASSWD(1)