1SHADOW(5)                File Formats and Conversions                SHADOW(5)
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NAME

6       shadow - shadowed password file
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DESCRIPTION

9       shadow is a file which contains the password information for the
10       system's accounts and optional aging information.
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12       This file must not be readable by regular users if password security is
13       to be maintained.
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15       Each line of this file contains 9 fields, separated by colons (“:”), in
16       the following order:
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18       login name
19           It must be a valid account name, which exist on the system.
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21       encrypted password
22           This field may be empty, in which case no passwords are required to
23           authenticate as the specified login name. However, some
24           applications which read the /etc/shadow file may decide not to
25           permit any access at all if the password field is empty.
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27           A password field which starts with an exclamation mark means that
28           the password is locked. The remaining characters on the line
29           represent the password field before the password was locked.
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31           Refer to crypt(3) for details on how this string is interpreted.
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33           If the password field contains some string that is not a valid
34           result of crypt(3), for instance ! or *, the user will not be able
35           to use a unix password to log in (but the user may log in the
36           system by other means).
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38       date of last password change
39           The date of the last password change, expressed as the number of
40           days since Jan 1, 1970 00:00 UTC.
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42           The value 0 has a special meaning, which is that the user should
43           change her password the next time she will log in the system.
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45           An empty field means that password aging features are disabled.
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47       minimum password age
48           The minimum password age is the number of days the user will have
49           to wait before she will be allowed to change her password again.
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51           An empty field and value 0 mean that there are no minimum password
52           age.
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54       maximum password age
55           The maximum password age is the number of days after which the user
56           will have to change her password.
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58           After this number of days is elapsed, the password may still be
59           valid. The user should be asked to change her password the next
60           time she will log in.
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62           An empty field means that there are no maximum password age, no
63           password warning period, and no password inactivity period (see
64           below).
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66           If the maximum password age is lower than the minimum password age,
67           the user cannot change her password.
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69       password warning period
70           The number of days before a password is going to expire (see the
71           maximum password age above) during which the user should be warned.
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73           An empty field and value 0 mean that there are no password warning
74           period.
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76       password inactivity period
77           The number of days after a password has expired (see the maximum
78           password age above) during which the password should still be
79           accepted (and the user should update her password during the next
80           login).
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82           After expiration of the password and this expiration period is
83           elapsed, no login is possible for the user. The user should contact
84           her administrator.
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86           An empty field means that there are no enforcement of an inactivity
87           period.
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89       account expiration date
90           The date of expiration of the account, expressed as the number of
91           days since Jan 1, 1970 00:00 UTC.
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93           Note that an account expiration differs from a password expiration.
94           In case of an account expiration, the user shall not be allowed to
95           login. In case of a password expiration, the user is not allowed to
96           login using her password.
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98           An empty field means that the account will never expire.
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100           The value 0 should not be used as it is interpreted as either an
101           account with no expiration, or as an expiration on Jan 1, 1970.
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103       reserved field
104           This field is reserved for future use.
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FILES

107       /etc/passwd
108           User account information.
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110       /etc/shadow
111           Secure user account information.
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113       /etc/shadow-
114           Backup file for /etc/shadow.
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116           Note that this file is used by the tools of the shadow toolsuite,
117           but not by all user and password management tools.
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SEE ALSO

120       chage(1), login(1), passwd(1), passwd(5), pwck(8), pwconv(8),
121       pwunconv(8), su(1), sulogin(8).
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125shadow-utils 4.8.1                11/16/2020                         SHADOW(5)